Nucleus Taeniae Research Articles

Distribution of aromatase‐immunoreactive cells in the forebrain of zebra finches (Taeniopygia guttata): Implications for the neural action of steroids and nuclear definition in the avian hypothalamus

Cells immunoreactive for the enzyme aromatase were localized in the forebrain of male zebra finches with the use of an immunocytochemistry procedure. Two polyclonal antibodies, one directed against human placental aromatase and the other directed against quail recombinant aromatase, revealed a heterogeneous distribution of the enzyme in the telencephalon, diencephalon, and mesencephalon. Staining was enhanced in some birds by the administration of the nonsteroidal aromatase inhibitor, R76713 (racemic Vorozole) prior to the perfusion of the birds as previously described in Japanese quail. Large numbers of cells immunoreactive for aromatase were found in nuclei in the preoptic region and in the tuberal hypothalamus. A nucleus was identified in the preoptic region based on the high density of aromatase immunoreactive cells within its boundaries that appears to be homologous to the preoptic medial nucleus (POM) described previously in Japanese quail. In several birds alternate sections were stained for immunoreactive vasotocin, a marker of the paraventricular nucleus (PVN). This information facilitated the clear separation of the POM in zebra finches from nuclei that are adjacent to the POM in the preoptic area-hypothalamus, such as the PVN and the ventromedial nucleus of the hypothalamus. Positively staining cells were also detected widely throughout the telencephalon. Cells were discerned in the medial parts of the ventral hyperstriatum and neostriatum near the lateral ventricle and in dorsal and medial parts of the hippocampus. They were most abundant in the caudal neostriatum where they clustered in the dorsomedial neostriatum, and as a band of cells coursing along the dorsal edge of the lamina archistriatalis dorsalis. They were also present in high numbers in the ventrolateral aspect of the neostriatum and in the nucleus taeniae. None of the telencephalic vocal control nuclei had appreciable numbers of cells immunoreactive for aromatase within their boundaries, with the possible exception of a group of cells that may correspond to the medial part of the magnocellular nucleus of the neostriatum. The distribution of immunoreactive aromatase cells in the zebra finch brain is in excellent agreement with the distribution of cells expressing the mRNA for aromatase recently described in the finch telencephalon. This widespread telencephalic distribution of cells immunoreactive for aromatase has not been described in non-songbird species such as the Japanese quail, the ring dove, and the domestic fowl. © 1996 John Wiley & Sons, Inc.

Distribution of aromatase-immunoreactive cells in the forebrain of zebra finches (Taeniopygia guttata): implications for the neural action of steroids and nuclear definition in the avian hypothalamus.

Cells immunoreactive for the enzyme aromatase were localized in the forebrain of male zebra finches with the use of an immunocytochemistry procedure. Two polyclonal antibodies, one directed against human placental aromatase and the other directed against quail recombinant aromatase, revealed a heterogeneous distribution of the enzyme in the telencephalon, diencephalon, and mesencephalon. Staining was enhanced in some birds by the administration of the nonsteroidal aromatase inhibitor, R76713 racemic Vorozole) prior to the perfusion of the birds as previously described in Japanese quail. Large numbers of cells immunoreactive for aromatase were found in nuclei in the preoptic region and in the tuberal hypothalamus. A nucleus was identified in the preoptic region based on the high density of aromatase immunoreactive cells within its boundaries that appears to be homologous to the preoptic medial nucleus (POM) described previously in Japanese quail. In several birds alternate sections were stained for immunoreactive vasotocin, a marker of the paraventricular nucleus (PVN). This information facilitated the clear separation of the POM in zebra finches from nuclei that are adjacent to the POM in the preoptic area-hypothalamus, such as the PVN and the ventromedial nucleus of the hypothalamus. Positively staining cells were also detected widely throughout the telencephalon. Cells were discerned in the medial parts of the ventral hyperstriatum and neostriatum near the lateral ventricle and in dorsal and medial parts of the hippocampus. They were most abundant in the caudal neostriatum where they clustered in the dorsomedial neostriatum, and as a band of cells coursing along the dorsal edge of the lamina archistriatalis dorsalis. They were also present in high numbers in the ventrolateral aspect of the neostriatum and in the nucleus taeniae. None of the telencephalic vocal control nuclei had appreciable numbers of cells immunoreactive for aromatase within their boundaries, with the possible exception of a group of cells that may correspond to the medial part of the magnocellular nucleus of the neostriatum. The distribution of immunoreactive aromatase cells in the zebra finch brain is in excellent agreement with the distribution of cells expressing the mRNA for aromatase recently described in the finch telencephalon. This widespread telencephalic distribution of cells immunoreactive for aromatase has not been described in non-songbird species such as the Japanese quail, the ring dove, and the domestic fowl.

Telencephalic afferents to the caudolateral neostriatum of the pigeon

The pigeon caudolateral neostriatum (NCL) shares a dopaminergic innervation with mammalian frontal cortical areas and is implicated in the regulation of avian cognitive behavior. Retrograde tracing methods were used to identify forebrain projections to NCL and to suggest a possible role of this area in mediating spatial behavior. NCL receives telencephalic projections from the hyperstriatum accessorium, cells along the border of hyperstriatum dorsale and hyperstriatum ventrale, anterolateral hyperstriatum adjacent to the vallecula, confined cell groups within the anterior neostriatum, and subdivisions of the archistriatum In addition, labeling of a small number of large cells near the fasciculus prosencephali lateralis was observed at the level of the anterior commissure. In accordance with previous studies, projections of subtelencephalic areas were revealed to originate from the thalamic posterior dorsolateral nucleus and nucleus subrotundus, as well as from the tegmental nucleus pedunculopontinus and locus coeruleus. Forebrain connections of NCL show that somatosensory, visual, and olfactory information can combine in this division of the neostriatum. NCL is therefore suited to participate in a neural circuit that regulates spatial behavior. Moreover, the present study reveals that NCL is reached by a limbic projection from the nucleus taeniae. This projection also suggests similarity between NCL and mammalian frontal cortical areas.

Efferent connectivity of the hippocampal formation of the zebra finch (Taenopygia guttata): An anterograde pathway tracing study usingPhaseolus vulgaris leucoagglutinin

The avian hippocampal formation (HP) is considered to be homologous to the mammalian hippocampus, being involved in memory formation and spatial memory in particular. The subdivisions and boundaries of the pigeon hippocampus have been defined previously by various morphological methods to detect further similarities with the mammalian homologue. We studied the efferent projections of the zebra finch hippocampus by applying Phaseolus vulgaris leucoagglutinin, and three main subdivisions were distinguished on the basis of the connectivity patterns. Dorsolateral injections gave rise to projections innervating the rostralmost extension of the HP, a laminar complex including the dorsal and ventral hyperstriata and the lamina frontalis superior, the rostral lobus parolfactorius, the medial and ventral paleostriatal regions, the lateral septal nucleus, the nucleus of the diagonal band, the dorsolateral corticoid area, the archistriatum posterius, and the nucleus taeniae in the telencephalon. In the diencephalon, labelled axons were seen in the periventricular and lateral hypothalamus, including the lateral mammillary nuclei, and in the dorsolateral and the dorsomedial posterior thalamic nuclei, whereas, in the midbrain, only the area ventralis of Tsai contained hippocampal fibres. With the exception of the bilateral archistriatal efferents, all projections were ipsilateral. Dorsomedial injections gave rise to a local fibre system that was almost completely restricted to the ipsilateral hippocampal formation. In addition, lectin-containing fibres continued in the dorsal septal region and a thin band in the hyperstriatum accessorium, adjacent to the lateral ventricle. Ventral injections gave rise to axons innervating ipsilaterally the dorsolateral subdivision, and bilaterally the medial septal nuclei and the contralateral ventral hippocampus.

Distribution of serotonin-immunoreactivity in the brain of the pigeon (Columba livia).

The distribution of serotonin (5-HT)-containing perikarya, fibers and terminals in the brain of the pigeon (Columba livia) was investigated, using immunohistochemical and immunofluorescence methods combined with retrograde axonal transport. Twenty-one different groups of 5-HT immunoreactive (IR) cells were identified, 2 of which were localized at the hypothalamic level (periventricular organ, infundibular recess) and 19 at the tegmental-mesencephalic and rhombencephalic levels. Ten of the cell groups were situated within the region of the midline from the isthmic to the posterior rhombencephalic level and constituted the raphe system (nucleus annularis, decussatio brachium conjunctivum, area ventralis, external border of the nucleus interpeduncularis, zona peri-nervus oculomotorius, zona perifasciculus longitudinalis medialis, zona inter-flm, nucleus linearis caudalis, nucleus raphe superior pars ventralis, nucleus raphe inferior). The 9 other cell populations belonged to the lateral group and extended from the posterior mesencephalic tegmentum to the caudal rhombencephalon [formatio reticularis mesencephali, nucleus ventrolateralis tegmenti, ectopic area (Ec) of the nucleus isthmo-opticus (NIO), nucleus subceruleus, nucleus ceruleus, nucleus reticularis pontis caudalis, nucleus vestibularis medialis, nucleus reticularis parvocellularis and nucleus reticularis magnocellularis]. Combining the retrograde axonal transport of rhodamine beta-isothiocyanate (RITC) after intraocular injection and immunohistofluorescence (fluoresceine isothiocyanate: FITC/5-HT) showed the centrifugal neurons (NIO, Ec) to be immunonegative. Serotonin-IR fibers and terminals were found to be very broadly distributed within the brain and were particularly prominent in several structures of the telencephalon (archistriatum pars dorsalis, nucleus taeniae, area parahippocampalis, septum), diencephalon (nuclei preopticus medianus, magnocellularis, nucleus geniculatus lateralis pars ventralis, nucleus triangularis, nucleus pretectalis), mesencephalon-rhombencephalon (superficial layers of the optic tectum, nucleus ectomamillaris, nucleus isthmo-opticus and in most of the cranial nerve nuclei). Comparing the present results with those of previous studies in birds suggests some major serotonin-containing pathways in the avian brain and clarifies the possible origin of the serotonin innervation of some parts of the brain. Moreover, comparing our results in birds with those obtained in other vertebrate species shows that the organization of the serotoninergic system in many regions of the avian brain is much like that found in reptiles and mammals.

Critical re-examination of the distribution of aromatase-immunoreactive cells in the quail forebrain using antibodies raised against human placental aromatase and against the recombinant quail, mouse or human enzyme

Mouse and quail aromatase cDNAs were isolated from libraries of mouse ovary and quail brain by using a human aromatase cDNA fragment (hA-24) as a probe. These three cDNAs were inserted into plasmid vectors and expressed in Escherichia coli. Antisera against these purified recombinant proteins were raised in rabbit and purified by ammonium sulfate fractionation and affinity chromatography. The three antibodies directed against recombinant human, mouse and quail proteins were used to visualize aromatase-immunoreactive cells in the quail brain. They were compared with the antibody raised against human placental aromatase used in previous experiments and with another antibody recently developed by similar methods. The signal obtained with all antibodies was completely abolished by preadsorption with the homologous recombinant antigens and the signal produced by the two antibodies raised against placental aromatase was similarly abolished by a preadsorption with recombinant quail aromatase. The antibodies raised against recombinant proteins identified the major groups of aromatase cells previously described in the quail brain. The antibodies directed against the mouse and quail antigen identified more positive cells and stained them more densely than the antibodies raised against human recombinant antigen or purified placental aromatase. The new cell groups identified by the antibody raised against quail recombinant aromatase were located in an area ventral to the fasciculus prosencephali lateralis, the nucleus accumbens, the paleostriatum ventrale, the nucleus taeniae, the area around the nucleus ovoidalis, the caudal tuber and the mesencephalic central gray. A critical re-examination of the distribution and nomenclature of the aromatase-positive cells is proposed based on these new findings.

Connections of the Olfactory Bulb in the Chinook Salmon <i>(Oncorhynchus tshawytscha)</i>

This report describes the connections of the olfactory bulb in juvenile chinook salmon (Oncorhynchus tshawytscha) as revealed by the retrograde and anterograde transport of biotinylated dextran amine (BDA). Pressure injections of BDA to discrete locations within the bulb reveal that the olfactory bulb projects via medial and lateral tracts to various regions of the dorsal and ventral telencephalon as well as to the diencephalon. Terminal-like boutons are present in the ventral, dorsal, lateral and supracommissural nuclei of the ventral telencephalon and in the lateral-ventral and posterior zones of the dorsal telencephalon. There is also a projection to the nucleus taenia and to the contralateral olfactory bulb. A diencephalic terminal field occurs in the posterior tuberal region of the ventral diencephalon. Olfactory bulb fibers in the preoptic region have axonal varicosities near neurons containing releasing hormones. A synaptic connection is suggested allowing for the possibility that output from the olfactory bulb may directly modulate the activity of these neurons. Telencephalic injections of BDA are used to determine the origins of olfactory bulb efferents. Neurons are retrogradely labeled by BDA in a Golgi-like manner, allowing one to visualize the morphology of olfactory bulb efferents. Three types of neurons in the bulb are filled by injections into the posterior zone of the dorsal telencephalon: mitral cells and ruffed cells in the external cellular layer, and neurons in the internal cellular layer. Although it has been known that both mitral cells and neurons in the internal cellular layer project out of the bulb in teleosts, the use of BDA allowed for an accurate description of the morphology of these extrinsically projecting neurons. This is the first evidence that the ruffed cells in salmon project out of the bulb. The results of this study suggest that the secondary olfactory projections in chinook salmon are consistent with those in other teleosts with minor variations. The data also show that olfactory bulb efferents originate not solely from mitral cells in the external cellular layer but also from ruffed cells in the external cellular layer and neurons in the internal cellular layer. It is proposed that the extrinsically projecting neurons in the internal cellular layer constitute an anterior olfactory nucleus in salmon.

Radioautographic demonstration and localization of glucagon receptors in duck brain

The discovery of glucagon biosynthesis and receptors within mammalian brain has led one to suspect a neurotransmitter role for glucagon. In order to address this hypothesis in birds, we investigated the existence of glucagon receptors in duck brain by radioligand binding on fresh tissue sections and radioautography. Specific high-affinity [ 125I]glucagon binding sites similar to those in the liver were demonstrated in the avian brain. Mapping of these putative glucagon receptors revealed a discrete distributional pattern. Most of the [ 125I]glucagon binding capacity in duck brain is concentrated within the telencephalon, mainly in components of motor and limbic systems. Specific labeling densities were associated with avian equivalents of the mammalian pyramidal system (hyperstriatum accessorium; archistriatum intermedium and tractus occipitomesencephalicus) and extrapyramidal system (paleostriatum augmentatum, paleostriatum primitivum and lobus parolfactorius), as well as several limbic structures (hippocampal formation, nucleus taeniae and the caudal part of the archistriatum). Few glucagon-reactive foci were detected in the diencephalon (the nucleus dorsomedialis of hypothalamus, the two circumventricular organs, organum vasculosum of the lamina terminalis and median eminence and the nucleus habenularis medialis). These findings suggest that glucagon might be involved in the central control of somatic motricity and basic behaviors and point therefore to glucagon as a new neuroactive messenger in avian brain. The extensive difference between the distribution of glucagon binding sites observed in duck brain and that previously reported in rat brain suggests that glucagon does not subserve the same physiological role(s) in avian and mammalian brains.

Effects of steroidal and non steroidal aromatase inhibitors on sexual behavior and aromatase-immunoreactive cells and fibers in the quail brain

Castrated quail were treated with Silastic implants filled with testosterone (T) in association with injections of the aromatase inhibitors, R76713 (racemic vorozole; 1 mg/kg twice a day) or 4-hydroxyandrostenedione (OHA; 5 mg/bird twice a day). Control birds received no treatment (CX group) or were implanted with T capsules only (CX + T group). Both R76713 and OHA strongly inhibited the T-activated male copulatory behavior. This inhibition had the same magnitude in both groups. The growth of the cloacal gland, a strictly androgen-dependent process was not affected by these compounds. The treatments significantly affected the number of aromatase-immunoreactive (ARO-ir) cells in each of the six brain areas that were studied: the anterior and posterior parts of the sexually dimorphic medial preoptic nucleus (POM), the septal region, the bed nucleus of the stria terminalis (BNST) and the anterior and posterior parts of the tuber. This number was significantly increased in all areas by T. In agreement with our previous study, R76713 significantly inhibited this effect of T in the tuberal hypothalamus but not in the anterior POM nor in the BNST. By contrast the effect of T on the number of ARO-ir cells was completely blocked by OHA in all brain nuclei. The two inhibitors had statistically different effects in all brain regions. Like in a previous study, R76713 increased the intensity of the staining of all ARO-ir cells. This effect took several days to develop suggesting a progressive build-up of the enzyme concentration. This was also suggested by the fact that a rebound in aromatase activity was observed 16 to 24 h after a single injection of R76713. The increased immunoreactivity was not observed in OHA-treated birds. The denser immunoreactivity in R76713-treated birds and the better tissue preservation due to the aldehyde fixative that had been used provided here a clearer picture of the cellular and subcellular localization of ARO-ir material. This allowed to identify new groups of immunoreactive cells, namely in the nucleus accumbens, in the area of the paleostriatum ventrale, in the nucleus taeniae, in the medial and caudal hypothalamus and in the medial part of the mesencephalon and of the pons. Most of the immunoreactive material was located in perikarya but some of these cells were also surrounded by dense networks of ARO-ir fibers often associated with immunopositive punctate structures. These fibers and punctate structures were seen also in areas that were quite distant from the closest ARO-ir cells. They were detected in periventricular position throughout the preoptic area and hypothalamus.

Topographical distribution of reduced nicotinamide adenine dinucleotide phosphate‐diaphorase in the brain of the Japanese quail

The distribution of reduced nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase activity was histochemically investigated in the Japanese quail brain. This enzyme is now considered responsible for the synthesis of nitric oxide, a novel neural messenger whose distribution has not been described in the avian brain until now. The histochemical technique provides a simple and reliable method for staining selected populations of neurons throughout the avian brain. In the telencephalon several regions showed heavily stained NADPH-diaphorase positive neurons and processes. In particular the paleostriatal-paraolfactory lobe complex showed the greatest presence of both positive cells and processes. Neurons and processes were also observed in several regions of the hyperstriatum as well as in the archistriatal nucleus taeniae. Some regions, such as the ectostriatum and the hippocampus, had no positive elements. In the diencephalon, the magnocellular hypothalamic system, which in mammals shows NADPH-diaphorase activity, did not show any particular accumulation of reaction product. On the contrary, retinorecipient areas, such as the visual suprachiasmatic nucleus and the lateral geniculate complex, displayed a composite structure of both positive neurons and processes. The brainstem revealed a large NADPH-diaphorase positive population extending through the tegmental nuclei to the locus coeruleus and subcoeruleus. A complex organization was also observed in the optic lobe, where fusiform elements were distributed within the stratum griseum and superficialis of the tectum. In the medulla, a dense terminal field was observed at the level of the nucleus of the solitary tract, whereas scattered neurons were located within the reticular nuclei. Although the staining of neurons and tracts was highly selective, the positive cells did not correspond to any single known neurotransmitter, neuropeptide, or neuroactive molecule system. Several sensory pathways were heavily stained for the NADPH-diaphorase, including part of the olfactory, visual, and auditory pathways. The findings of the present study reveal that the NADPH-diaphorase-containing systems in the avian brain are organized according to a pattern comparable, because of its complexity, to that observed in mammals. However, important interspecific differences suggest that this novel neural system might be involved in diverse tasks.

Localization of NADPH‐diaphorase in the brain of the chicken

NADPH-diaphorase, an enzyme catalyzed reaction thought to reflect the activity of nitric oxide synthase in the mammalian nervous system, was mapped in the brain of the chicken. Intensely stained neurons and fibers were found in most parts of the telencephalon, in particular in the neostriatum, paleostriatum augmentatum, olfactory tubercle, lobus parolfactorius, hyperstriatum accessorium, and hyperstriatum ventrale. Medial to the nucleus taeniae, an accumulation of stained cells was observed that appeared to merge with a band of stained neurons located dorsal to the occipitomesencephalic tract. These are considered to belong to the nucleus interstitialis of the dorsal olfactory projection. Further caudally, neurons with different staining intensities were found in the lateral hypothalamic area, lateral mammillary nucleus, periventricular organ, ventral tegmental area, medial spiriform nucleus, optic tectum, isthmooptic nucleus, mesencephalic trigeminal nucleus, interpeduncular nucleus, and central gray of the mesencephalon. A particularly dense cluster of NADPH-diaphorase positive neurons was located in the locus coeruleus. It is proposed that these might represent cholinergic cells intermingled with catecholaminergic neurons, thus forming the avian counterpart of the tegmental cholinergic nuclei of mammals. Several NADPH-diaphorase reactive neurons were seen in the parabrachial nucleus and medial and dorsal vestibular nucleus, as well as scattered in the reticular formation. In the caudal medulla, intensely stained cells were grouped around the central canal. Therefore the pattern of expression of NADPH-diaphorase, and thus possibly of nitric oxide synthase, within the avian and mammalian brain might be largely conserved.

Immunohistochemical localization of chicken gonadotropin‐releasing hormones I and II (cGnRH I and II) in turkey hen brain

The distribution of cells and fibers immunoreactive (ir) for either chicken gonadotropin-releasing hormone I (cGnRH I; [Gln8]GnRH) or II ([His5,Trp7,Tyr8]GnRH) was determined in brains of turkey hens to reveal whether these peptides occur in separate neuronal systems. ir-cGnRH I cells were located: along the medial aspect of the ventriculus lateralis, nucleus accumbens, and bed nucleus of the stria terminalis; ventral to the tractus septomesencephalicus and extending medially to the third ventricle, and caudally into the lateral hypothalamic area; and in a diffuse band extending from the nucleus preopticus medialis to the nucleus dorsomedialis anterior thalami. cGnRH I fibers were evident in these areas in addition to the hippocampus, nucleus subhabenularis medialis, nucleus ventromedialis hypothalami, and median eminence. Two groups of ir-cGnRH II cells were observed: a magnocellular group lying between the substantia grisea centralis and the nucleus ruber; and a parvicellular group lying medial to the nucleus of the basal optic root and extending into the lateral hypothalamic area. ir-cGnRH II fibers were prominent in limbic structures (cortex piriformis, lateral to nucleus taeniae, hippocampus); olfactory areas (tuberculum olfactorium, nucleus subhabenularis lateralis, nucleus septalis lateralis); areas that in other avian species have steroid-concentrating cells or receptors (medial edge of lobus parolfactorius, nucleus septalis medialis, nucleus periventricularis magnocellularis, nucleus dorsomedialis posterior thalami); and areas containing ir-GnRH I cells or fibers but not in median eminence. These results suggest that cGnRH I and II occur in separate neuronal systems and that cGnRH II does not directly promote pituitary gonadotropin secretion.

Localization of neuropeptide Y-immunoreactive cells and fibres in the brain of the Japanese quail

In the present study, we have demonstrated, by means of the biotin-avidin method, the widespread distribution of neuropeptide Y (NPY)-immunoreactive structures throughout the whole brain of the Japanese quail (Coturnix coturnix japonica). The prosencephalic region contained the highest concentration of both NPY-containing fibres and perikarya. Immunoreactive fibres were observed throughout, particularly within the paraolfactory lobe, the lateral septum, the nucleus taeniae, the preoptic area, the periventricular hypothalamic regions, the tuberal complex, and the ventrolateral thalamus. NPY-immunoreactive cells were represented by: a) small scattered perikarya in the telencephalic portion (i.e. archistriatal, neostriatal and hyperstriatal regions, hippocampus, piriform cortex); b) medium-sized cell bodies located around the nucleus rotundus, ventrolateral, and lateral anterior thalamic nuclei; c) small clustered cells within the periventricular and medial preoptic nuclei. The brainstem showed a less diffuse innervation, although a dense network of immunopositive fibres was observed within the optic tectum, the periaqueductal region, and the Edinger-Westphal, linearis caudalis and raphes nuclei. Two populations of large NPY-containing perikarya were detected: one located in the isthmic region, the other at the boundaries of the pons with the medulla. The wide distribution of NPY-immunoreactive structures within regions that have been demonstrated to play a role in the control of vegetative, endocrine and sensory activities suggests that, in birds, this neuropeptide is involved in the regulation of several aspects of cerebral functions.

Sex- and age-related differences in the activity of testosterone-metabolizing enzymes in microdissected nuclei of the zebra finch brain

Many effects of testosterone (T) in the zebra finch ( Taeniopygia guttata) can be mimicked by T-metabolites, mainly estradiol and 5α-dihydrotestosterone. We have therefore studied the neuroanatomical distribution of testosterone-metabolizing enzymes by means of the Palkovits punch technique combined with radioenzyme assay in the brain of adult and young male and female zebra finches. The activity of these enzymes was studied by a one-point assay in 5 nuclei of the song system (X, MAN, HVc, RA, ICo), 2 nuclei of the visual system (ectostriatum, nucleus rotundus) and in limbic and hypothalamic areas. Very noticeable was the presence of a very high aromatase activity in the hippocampal and parahippocampal region and in the nucleus taeniae and the absence of this enzyme in ICo. We found a higher aromatase activity in female than male HVc and RA and a higher 5α-reductase activity in MAN, HVc, RA and ICo of males compared to females. The 5α-reductase was more active in the preoptic area of females. A few sex-related differences in the activity of the 5β-reductase were also observed (higher activity in females than in males for area X and RA, but difference in the opposite direction for the ectostriatum). The statistical significance of these differences depended, to some extent, on the statistical technique used to demonstrate them, with the sex differences in RA being by far the most robust ones. Many age-related metabolic differences were also detected but these do not have a clear interpretation since the K m of these enzymes also changes with age. Extremely low levels of 5β-reductase activity were found in the nuclei of the visual system in adult birds while this enzymatic activity was very high in yound birds. The biological significance of this change with age remains obscure. Correlations are thus observed between the neuroanatomical distribution of T-metabolizing enzymes and of androgen and estrogen receptors with the important exception of ICo which has no aromatase but contains high concentrations of estrogen receptors. Testosterone-metabolizing enzymes are however also present in areas which are not known as steroid targets.

Neuroanatomical regions of the chick brain involved in monitoring amino acid deficient diets

Chicks fed a diet deficient in tryptophan will reduce food intake dramatically. Chicks will select a balanced diet over one that is deficient in tryptophan (trp). The amygdala and prepiriform cortex have been implicated in monitoring amino acid (AA) balanceand hence food intake in rats. Therefore, comparable regions of the chick brain were studied to determine if they were involved in monitoring AA deficient diets. In each of four experiments, 48 chicks were used (24 experimentally-operated and 24 sham-operated controls). After starting on a commercial diet, chicks were fed semipurified diets: balanced (bal) or trp deficient (def). The following dietary regimen was followed in all experiments in both pre- and postoperatively; 1. 1) bal diet for an adjustment period; 2. 2) bal diet for 1–2 days; 3. 3) def diet for 2–3 days; 4. 4) choice of both diets presented simultaneously. This was followed by ablation of a brain region and then a repetition of the dietary regimen. Brain regions ablated or isolated include the nucleus taeniae (Tn), piriform cortex (CPi), frontal archistriatum (FA) and ventral archistriatum (AV). No differences in selection were observed when lesions ablating the FA, AV or Tn were performed. A significant decrease in selection of the bal diet was observed after knife cuts which isolated the piriform cortex from medial connections. It is suggested that this brain region may be involved in monitoring AA profiles in the plasma.

A comparison of aromatase, 5 alpha-, and 5 beta- reductase activities in the brain and pituitary of male and female quail (C. c. japonica).

In numerous vertebrate species including Japanese quail (Coturnix coturnix japonica), actions of testosterone (T) on neuroendocrine target tissues are mediated in part by conversion to estrogenic and androgenic metabolites. In order to assess which pathways were favored in each identified androgen target area in quail brain and whether there were discernible sex differences, we developed an assay for simultaneously quantifying aromatase, 5 alpha-, and 5 beta-reductase. In addition, we made the first definitive identification of aromatase in quail pituitary and compared all three enzyme activities in the pituitary of males and females. Enzymes were measured in tissue homogenates by the conversion of [3H]androstenedione to [3H]estrone, [3H]5 alpha-androstanedione, and 5 beta-androstanedione. Aromatase activity was restricted to limbic tissues (anterior hypothalamus greater than posterior hypothalamus greater than septum greater than archistriatum containing nucleus taenia) while hyperstriatum, cerebellum, and midbrain containing nucleus intercollicularis were aromatase-negative. Quail pituitary aromatized androgen at rates equivalent to anterior hypothalamus/pre-optic area (aHPOA). 5 alpha- and 5 beta-reductase were present in all tissues tested. Aromatase was significantly higher in aHPOA and pituitary of males, whereas 5 alpha-reductase was significantly higher in female pituitary. These data suggest that a complex of androgen-metabolizing enzymes controls the neuroanatomic (spatial) distribution of active hormone in neuroendocrine tissues and that quantitative differences between males and females may account for sex differences in behavior.

Telencephalic projections from midbrain and isthmal cell groups in the pigeon. I. Locus coeruleus and subcoeruleus

Horseradish peroxidase (HRP) and amino acid autoradiography were used in pigeon to determine the trajectories and projection patterns of neurons within the locus coeruleus and subcoeruleus nuclei upon the cerebral hemispheres. The specific cell groups investigated include the locus coeruleus (LoC), nucleus subcoeruleus dorsalis, and nucleus subcoeruleus ventralis. Efferents from each of these nuclei ascend to the telencephalon via the medial and lateral forebrain bundles, ansa lenticularis, and the quintofrontal and occipitomesencephalic tracts. A separate dorsally situated bundle derived from LoC neurons reaches many dorsal thalamic nuclei. The telencephalic projections of the LoC and subcoeruleus nuclei are bilateral and symmetrical, although projections to the contralateral hemisphere are sparse. Crossing fibers project to contralateral targets primarily via the dorsal supraoptic decussation and along the dorsal and ventral margins of the anterior commissure. Within the telencephalon, the following neural structures receive input from neurons in the LoC and subcoeruleus cell groups: the paleostriatal complex including the paleostriatum augmentatum and lobus parolfactorius, septal nuclei, nucleus accumbens, olfactory tubercle, hippocampus and parahippocampal area, nucleus taeniae, dorsal archistriatum, lateral neostriatum, hyperstriatum dorsale, hyperstriatum ventrale, and preoptic area. Large portions of the cerebral hemispheres including the hyperstriatum accessorium, much of the neostriatum and hyperstriatum ventrale, and all but the dorsal portion of the archistriatum receive little or no input from either the locus coeruleus or subcoeruleus cell groups. This is apparently different from the condition in mammals in which virtually all cortical fields receive input from neurons within the LoC. Moreover, the pattern of projections of the subcoeruleus nuclei upon telencephalic fields described here as well as recent histochemical data suggest that these cell groups are comparable to the lateral tegmental (A8) cell group of mammals rather than to the mammalian subcoeruleus nuclei.

Connections of the pigeon dorsomedial forebrain studied with WGA‐HRP and 3H‐proline

The afferent-efferent connections of the pigeon dorsomedial forebrain, which is composed of the "hippocampus" (Hp) and "parahippocampus" (APH), presumed homologues of the mammalian hippocampal complex, were studied. Afferent projections were identified by wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) and efferent projections were identified by 3H-proline and WGA-HRP. In addition to identified intrinsic connections within Hp and APH, both Hp and APH were found to be in receipt of ipsilateral forebrain afferents from each other, the hyperstriatum accessorium, nucleus of the diagonal band, nucleus taeniae, and area corticoidea dorsolateralis. Only Hp received input from the contralateral Hp while only APH received input from the ipsilateral hyperstriatum dorsale and archistriatum, pars ventralis. Both Hp and APH received ipsilateral diencephalic afferents from the nucleus mamillaris lateralis, stratum cellulare internum, nucleus lateralis hypothalami, and nucleus paramedianus internus thalami. Only APH received bilateral input from the nucleus superficialis parvicellularis (this nucleus may send a small projection to Hp) and nucleus dorsolateralis anterior thalami, pars medialis, and an ipsilateral projection from the nucleus subrotundus. Brainstem afferents to Hp and APH included ipsilateral projections from the area ventralis (Tsai) nucleus reticularis pontis oralis, nucleus raphes, nucleus subceruleus dorsalis, and nucleus centralis superior of Bechterew, and bilateral projections from the nucleus linearis caudalis and locus ceruleus, of which the nucleus subceruleus dorsalis, nucleus centralis superior of Bechterew, and locus ceruleus projected to APH only. Forebrain efferents from both Hp and APH were found to project ipsilaterally to the septum, the area of the fasciculus diagonalis Brocae, nucleus taeniae, and area corticoidea dorsolateralis. Only Hp appeared to send efferents to the contralateral septum and Hp, while only APH sent efferents to the hyperstriatum dorsale and the archistriatum. A hypothalamic projection from Hp and APH was found to partially terminate near the nucleus mamillaris lateralis. At the level of pathway connections, the results demonstrate a striking similarity between the avian dorsomedial forebrain and the dorsomedial cortex of reptiles and the mammalian hippocampus.

Immunohistochemical demonstration of serotonin-containing nerve fibers in the corpus striatum of the rat, cat and monkey

The discovery of glucagon biosynthesis and receptors within mammalian brain has led one to suspect a neurotransmitter role for glucagon. In order to address this hypothesis in birds, we investigated the existence of glucagon receptors in duck brain by radioligand binding on fresh tissue sections and radioautography. Specific high-affinity [125I]glucagon binding sites similar to those in the liver were demonstrated in the avian brain. Mapping of these putative glucagon receptors revealed a discrete distributional pattern. Most of the [125I]glucagon binding capacity in duck brain is concentrated within the telencephalon, mainly in components of motor and limbic systems. Specific labeling densities were associated with avian equivalents of the mammalian pyramidal system (hyperstriatum accessorium; archistriatum intermedium and tractus occipitomesencephalicus) and extrapyramidal system (paleostriatum augmentatum, paleostriatum primitivum and lobus parolfactorius), as well as several limbic structures (hippocampal formation, nucleus taeniae and the caudal part of the archistriatum). Few glucagon-reactive foci were detected in the diencephalon (the nucleus dorsomedialis of hypothalamus, the two circumventricular organs, organum vasculosum of the lamina terminalis and median eminence and the nucleus habenularis medialis). These findings suggest that glucagon might be involved in the central control of somatic motricity and basic behaviors and point therefore to glucagon as a new neuroactive messenger in avian brain. The extensive difference between the distribution of glucagon binding sites observed in duck brain and that previously reported in rat brain suggests that glucagon does not subserve the same physiological role(s) in avian and mammalian brains.

Organization of the telencephalon in the channel catfish, Ictalurus punctatus.

The cytoarchitectonics of the telencephalon of the channel catfish, Ictalurus punctatus, are described as a basis for experimental analysis of telencephalic afferents and efferents. The olfactory bulb comprises: (1) an outer layer of olfactory nerve fibers, (2) a glomerular layer, (3) an external cell layer, (4) an inner fiber layer, and (5) an internal cell layer. The telencephalic hemispheres comprise the areas ventralis and dorsalis telencephali. The area ventralis consists of: (1) a precommissural, periventricular zone including nucleus 'nother (Vn), the ventral nucleus (Vv), and the dorsal nucleus (Vd); (2) a precommissural, migrated zone of central (Vc) and lateral (VI) nuclei; (3) a supracommissural nucleus (Vs); (4) a caudal commissural zone of postcommissural (Vp) and intermediate (Vi) nuclei; and (5) a preoptic area (PP). The area dorsalis comprises: (1) medial (DM), (2) dorsal (Dd), (3) lateral [DL, containing dorsal (DLd), ventral (DLv), and posterior (DLp) regions], (4) posterior (DP), and (5) central (DC-1, -2, -3) areas. Nucleus taeniae (NT) is transitional between areas dorsalis and ventralis.