R Complex Research Articles

Overview of the main and accessory olfactory bulb projections in reptiles.

The present account is a review of the main and accessory olfactory bulb projections in reptiles. From previous studies by means of the classical degeneration techniques and recent studies using the autoradiographic method or the Phaseolus vulgarus-leucoagglutinin (PHA-L) tracing technique, it has become evident that, in the brain of reptiles, the vomeronasal and main olfactory systems are segregated. Moreover, the PHA-L studies have demonstrated that the main olfactory bulbs project not only to the anterior olfactory nucleus, the olfactory tubercle, and the lateral cortex, but also to the rostral portions of the external and central amygdaloid nuclei. The latter studies also provided evidence that, apart from a massive projection to the nucleus sphericus, at least in some reptilian species, the accessory olfactory bulbs project to the caudal portion of the central amygdaloid nucleus and the bed nucleus of the stria terminalis. A comparison of the olfactory projections between the various reptilian species studied revealed a considerable variation in the course of the main olfactory bulb efferents that reach the contralateral hemisphere.

The brain looks at diversity

This paper provides a neurobiological perspective on diversity and ethnic relations. Three neural metaphors, the hunter‐gather brain, the triune brain and the split brain, are used to account for biological tendencies which can create problems for multiethnic societies. It is argued that the neocortex can control these tendencies, but that such control requires considerable effort.

Narine occlusion decreases basal levels of fos protein in the cerebral cortex of the lizard Podarcis hispanica

Immunocytochemical study of cerebral cortex of the lizard Podarcis hispanica using an antibody directed to the M peptide of the rat c-Fos protein showed a distinct pattern of Fos distribution. Abundant Fos-immunoreactive neuronal nuclei were detected in the cell layers of the medial, the dorsal and the lateral cortices, whereas only a few nuclei were found in the cell layer of the dorsomedial cortex. The Fos immunoreactivity was characterized by Western blot analysis of nuclear extracts from lizard brain and showed a distinct band with an apparent molecular weight of 30,000. In band-shift assays, nuclear extracts from lizard brain were shown to contain AP-1 complexes. The basal expression of Fos immunoreactivity is related to sensory olfactory input in the cerebral cortex of the lizard since experiments with olfactory-deprived animals resulted in a complete absence of Fos immunoreactivity in the cortical areas.

Absence of maternal behavior in rats with lithium/pilocarpine seizure-induced brain damage: Support of MacLean's triune brain theory

Female rats, with and without maternal experience, received limbic seizure-inducing (SC) injections of lithium and pilocarpine. Following the subsequent parturitions, these rats displayed a complete absence of maternal behavior. Rats that did not display seizures after receiving the lithium/pilocarpine injections displayed behaviors that were comparable to normal controls. Although the multifocal limbic, thalamic, and cingulate damage abolished maternal care, there was no evidence of aberrant effects upon fecundity, litter size, or mammary function; infanticide was negligible. The pattern of brain damage involves the evolutionarily more recent thalamocingulate system of mammals and supports MacLean's theory that these pathways are required for normal mother-offspring interaction.

Sexual dimorphisms in the soma size of neurons in the brain of whiptail lizards ( Cnemidophorus species)

Soma area was significantly larger in the anterior hypothalamus-preoptic area of male than female Cnemidophorus inornatus, and it was significantly larger in females than males in the ventromedial hypothalamus. These results parallel those on the volume of the brain areas in these animals, and therefore probably explain at least part of the dimorphisms seen in this sexually reproducing species. Soma size in parthenogenetic C. uniparens also parallels volume.

Asymmetric distribution of melatonin receptors in the brain of the lizard Anolis carolinensis

The pineal hormone melatonin may regulate seasonal reproduction and entrainment of circadian rhythms by binding to specific brain receptors. An analysis of melatonin receptor distribution in the lizard brain revealed an asymmetry of melatonin binding in the diencephalon. A high degree of melatonin binding was present in the left habenular nucleus, but no binding was observed in the habenulum of the right brain hemisphere. It is intriguing that the left habenular nucleus, in contrast to the right habenulum, both possesses a high density of melatonin receptors and receives primary photic input from the parietal eye. Similarly, the optic tectum, which receives primary visual input from the retina, is also rich in melatonin receptors. These observations suggest that the left habenulum is under dual control (neuronal and hormonal) of the parietal eye/pineal complex, and that melatonin may play a significant role in neural processing of visual information.

The Triune Brain in Evolution: Role in Paleocerebml Functions

The Triune Brain in Evolution: Role in Paleocerebml Functions

Distribution of neuropeptide Y-like immunoreactivity in the brain of the lizard Gallotia galloti.

The distribution of neuropeptide Y (NPY)-like immunoreactivity was studied in the brain of the lizard Gallotia galloti, in order to gain insight into the comparative topography of this peptide. Antisera against both NPY and its C-terminal flanking peptide (C-PON) were used, demonstrating a general coexistence of both peptides, as described in other vertebrates. Most NPY-like immunoreactive (NPY-LI) cell bodies were observed in the telencephalon, specifically in various olfactory structures, all cortices, septum, basal ganglia (except for the globus pallidus), the nucleus of the diagonal band of Broca, the amygdaloid complex, and the bed nucleus of the anterior commissure. NPY-LI cells were also seen in the preoptic and hypothalamic regions and the dorsal thalamus (mainly in the perirotundal belt), as well as in the mesencephalic tegmentum (in the ventral tegmental area, the substantia nigra, and the retrorubral area). NPY-LI fibers and terminals were widely distributed in the brain. All visual and auditory neuropiles were densely innervated. Specially dense plexuses were seen in the nucleus accumbens, the ventral pallidum, the suprachiasmatic and ventromedial hypothalamic nuclei, the nucleus medialis thalami, the left habenula, and the central nucleus of the torus semicircularis. Our analysis shows that the distribution of NPY-like immunoreactivity in the forebrain of Gallotia largely resembles that of other vertebrates, whereas differences are mainly observed in the brainstem. The widespread distribution of NPY in the lizard brain suggests several modulatory functional roles, either in local-circuit systems of the forebrain, or in various limbic, neuroendocrine, and sensory pathways.

Immunohistochemical demonstration of the presence and localization of diverse molecular forms of gonadotropin-releasing hormone in the lizard ( Podarcis s. sicula) brain

The immunoshistochemical presence and the distribution pattern of four different molecular forms of gonadotropin-releasing hormone (GnRH) were investigated in the brain of both sexes of the lizard, Podarcis s. sicula. Animals used in this study were collected in November and April, representing two different periods of the reproductive cycle. The antisera used were those raised against synthetic mammalian GnRH, chicken GnRH-I and II, and salmon GnRH. Strong immunoreaction was obtained for salmon, chicken-I, and chicken-II GnRHs, whereas a very weak reaction was seen for the mammalian form of GnRH. The distribution of immunoreactive-GnRH perikarya and fibers did not vary with the sex, the reproductive condition of the animals, or the antiserum used. Also, the intensity of immunoreaction with any one antiserum was quite similar in both periods of the year and in all brains examined. The immunoreactive perikarya were seen as two distinct groups, one in the mesencephalon and the other in the infundibulum. Immunoreactive fiber endings were seen in the telencephalon, the optic tectum, the anterior preoptic area, the median eminence, the central grey matter, the rhombencephalon, and the cerebellum. No immunoreactive perikarya were seen in the telencephalon or the anterior preoptic area.

Histochemical distribution of zinc in the brain of the rainbow trout, Oncorhynchos myciss. I. The telencephalon.

The present paper which describes the distribution of zinc in the telencephalon of the rainbow trout, Oncorhynchos myciss, is the first report on the distribution of a heavy metal in the fish brain. Zinc was demonstrated histochemically by silver enhancement using the Neo-Timm method. The staining was mainly confined to the neuropil, but both moderately and intensely stained nerve cell bodies were of common occurrence. Stained fibers were never observed. The staining revealed a specific distribution pattern which could easily be correlated with the telencephalic nuclei defined on the basis of cytoarchitectural features. However, the telencephalon stained much more weakly than the rest of the brain, in striking contrast to the situation in the reptilian, mammalian, and avian brain. In these classes, high staining intensities are observed almost exclusively in the telencephalon. The staining was essentially restricted to the nuclei of the ventral telencephalic area. In the dorsal telencephalic area, only the medial and central zones and medial part of the posterior zone showed comparable staining intensities. The Neo-Timm staining pattern lends support to the view that the pallio-subpallial boundary is between the medial and dorsal zones of the dorsal telencephalic area. The distribution of zinc has been compared with the terminal field of afferent projections, known from experimental mapping, and also with the distribution of substance P and vasoactive intestinal peptide. Finally, the possible functional implications of zinc in synaptic vesicles are considered.

The relationship between reproductive state and “sexually” dimorphic brain areas in sexually reproducing and parthenogenetic whiptail lizards

The anterior hypothalamus-preoptic area and ventromedial hypothalamus are sexually dimorphic in the reproductively active whiptail lizard Cnemidophorus inornatus. The anterior hypothalamus-preoptic area, which is involved in the control of male-typical copulatory behaviors, is larger in males, whereas the ventromedial hypothalamus, which is involved in the control of female-typical receptivity, is larger in females. In the parthenogenetic whiptail lizard C. uniparens, which is a direct descendant of C. inornatus and exhibits both male-like and female-like pseudosexual behaviors, both brain areas are comparable in size to those of female C. inornatus. This study was conducted to determine whether these brain areas change in size in either species or sex during a time of year when these animals are reproductively inactive, or after removal of the gonads. In male C. inornatus both brain areas changed during reproductive inactivity (either seasonally or surgically induced) and became equivalent to the size characteristic of reproductively active female C. inornatus. When corrected for brain size, the anterior hypothalamus-preoptic area was significantly smaller in intact hibernating and castrated males than in intact males from the summer breeding season. Conversely, the ventromedial hypothalamus was significantly larger in intact hibernating and castrated males than in intact males from the summer breeding season. The two brain areas were not significantly different among the groups of female C. inornatus or parthenogenetic C. uniparens. These results suggest that 1) the brain of whiptail lizards may differentiate seasonally and 2) the female state may be a neutral one to which the male brain reverts during reproductive inactivity.

Age-related changes in brain and spinal cord lipids of the male garden lizard

The lipid composition (cholesterol, phospholipid triglyceride and fatty acids) of brain and spinal cord of the male garden lizard was traced during maturation and ageing. The total brain cholesterol content of both the tissues showed a significant rise during maturation, remaining almost constant thereafter. The free cholesterol content of the brain increased between middle and old age and that of the spinal cord increased during maturation. The esterified cholesterol content of the brain increased during maturation, the same parameter being not age-dependent in the spinal cord. While in the brain the phospholipid content increased during maturation followed by a decrease in old age, it showed a reverse trend in the spinal cord. The level of triglyceride in the brain declined during maturation followed by an increase in old age with no appreciable age change in the spinal cord. A comparison between young and old age-groups revealed a decrease in fatty acid content of the brain. A similar trend of decline was observed during maturation in the spinal cord. The pattern of age changes in the lipid profile of nervous tissue of the lizard, a non-mammalian vertebrate, almost conform to the pattern observed in a majority of mammals.

Amino acid uptake systems in lizard and chick brain cells

The uptake of seven amino acids, alpha-aminoisobutyric acid (AIB), cyclo-leucine (cyclo-Leu), gamma-aminobutyric acid (GABA), glycine (Gly), glutamic acid (Glu), lysine (Lys), and taurine (Tau), representatives of different amino acid transport systems, was studied in slices of brain from Tokay lizards and White Leghorn chicks. In descending order, the rate of the initial uptake of the amino acids in both species was Glu greater than Gly greater than GABA greater than Cyclo-Leu greater than AIB greater than Lys greater than Tau. The substrate specificities and the differences in sodium and temperature dependence of the uptake of the amino acids indicate the presence of several distinct amino acid transport systems, some sodium-dependent and some sodium-independent. The structural specificity of amino acid transport classes in the brain of these species is similar to that in other vertebrate brain preparations.

Homology and Evolutionary Origins of the 'Neocortex'

The telencephalon of mammals is characterized by the presence of a hexalaminated structure on its external surface, with specific auditory, visual, somatosensory and motor regions. Due to its seeming unique presence in mammals, it is frequently designated as the neocortex. The evolutionary origins of the so-called neocortex have long puzzled comparative neuroanatomists, in view of the seeming absence of a neocortical-like anlage in nonmammalian amniotes. The resolution of this puzzle requires analysis of both adult and embryonic brains. Experimental neuroanatomical, physiological and behavioral methods applied to adult avian and reptilian brains have finally clarified several fundamental questions regarding the origins of 'neocortex' and have indicated that these origins can be viewed as consequent to two separate events: (1) The elaboration of constituent neuronal populations and their associated connections that are common to the telencephalae of both nonmammalian and mammalian amniotes. In mammals these populations are found within the so-called neocortex. In birds and reptiles, most of these neurons are found within the dorsal and dorsolateral ventricular ridges (DVR and DLVR). (2) In mammals, the components of the DVR and DLVR are incorporated into the thin overlying pallium to form a laminated 'neocortex'. Analysis of development in domestic chicks suggests that the DVR is one of several prosencephalic neuromeres ('Prosomeres') that contribute to the ontogeny of comparable structures in birds. Perhaps in mammals, as well, cortical development is consequent to incorporation of these several prosomeres into proliferative ependyma of the pallial mantle.

Solubilization and Purification of Melatonin Receptors from Lizard Brain*

Melatonin receptors in lizard brain were identified and characterized using 125I-labeled melatonin ([125I]MEL) after solubilization with the detergent digitonin. Saturation studies of solubilized material revealed a high affinity binding site, with an apparent equilibrium dissociation constant of 181 +/- 45 pM. Binding was reversible and inhibited by melatonin and closely related analogs, but not by serotonin or norepinephrine. Treatment of solubilized material with the non-hydrolyzable GTP analog, guanosine 5'-(3-O-thiotriphosphate) (GTP-gamma-S), significantly reduced receptor affinity. Gel filtration chromatography of solubilized melatonin receptors revealed a high affinity, large (Mr 400,000) peak of specific binding. Pretreatment with GTP-gamma-S before solubilization resulted in elution of a lower affinity, smaller (Mr 150,000) peak of specific binding. To purify solubilized receptors, a novel affinity chromatography resin was developed by coupling 6-hydroxymelatonin with Epoxy-activated Sepharose 6B. Using this resin, melatonin receptors were purified approximately 10,000-fold. Purified material retained the pharmacologic specificity of melatonin receptors. These results show that melatonin receptors that bind ligand after detergent treatment can be solubilized and substantially purified by affinity chromatography.

Sexually Dimorphic Areas in the Brain of Whiptail Lizards

The whiptail lizard species Cnemidophorus inornatus exhibits sexually dimorphic mating behaviors. We report that complementary sexual dimorphisms exist in two hypothalamic regions in male and female C. inornatus. The anterior hypothalamus-preoptic area (AH-POA), which is involved in male-typical mounting and intromission behaviors, is larger in males. The ventromedial hypothalamus (VMH), which controls female-typical receptivity, is larger in females. The all-female whiptail lizard Cnemidophorus uniparens, a direct descendant of C. inornatus, regularly and reliably displays both male-like mounting and female-like receptive (pseudosexual) behaviors. Rather than having a male-like AH-POA, however, the AH-POA as well as the VMH of C. uniparens resemble that of female C. inornatus. The biological basis of pseudosexual behavior in the parthenogen appears to be due to an unusual sensitivity to ovarian progesterone rather than to a difference in brain morphology.

Microvascular Geometry in the Brain of the Lizard Trachydosaurus-Rugosus

The vasculature and microvasculature in the central nervous system of the lizard Trnchydosaurus rugosus was examined by means of scanning electron microscopy of vascular corrosion casts. The arterial supply to the brain is from paired internal carotids. Secondary branches from these feeder arteries form a network over the surface of the lizard brain, giving rise to artery-vein vessel pairs. The vessel pairs bend at right angles to the brain surface, giving rise to terminal arteriole-venular pairs which penetrate the brain substance. Capillaries arise at fairly regular intervals along the vessel pairs, each originating from the arteriole and terminating in the venule at a site contiguous with its origin from the arteriole. In this way all of the capillaries in the central nervous system of the lizard form countercurrent loops. Anastomotic connections between arteriole-venular pairs do not occur, each arterial vessel being an end artery.

Reptilian dorsal column nucleus lacks GAD immunoreactive neurons

Brains of reptiles, Caiman crocodilus, were processed by standard immunocytochemical methodology using a polyclonai antibody to glutamic acid decarboxylase (GAD) as well as several monoclonal antibodies to GAD. No neurons immunoreactive for GAD, GAD(+), were observed in the dorsal column nucleus, although GAD(+) puncta were seen. These findings suggest that in Caiman, the dorsal column nucleus, like the dorsal thalamus, lacks local circuit neurons.

Guanine nucleotide-binding protein regulation of melatonin receptors in lizard brain.

Melatonin receptors were identified and characterized in crude membrane preparations from lizard brain by using 125I-labeled melatonin (125I-Mel), a potent melatonin agonist. 125I-Mel binding sites were saturable; Scatchard analysis revealed high-affinity and lower affinity binding sites, with apparent Kd of 2.3 +/- 1.0 x 10(-11) M and 2.06 +/- 0.43 x 10(-10) M, respectively. Binding was reversible and inhibited by melatonin and closely related analogs but not by serotonin or norepinephrine. Treatment of crude membranes with the nonhydrolyzable GTP analog guanosine 5'-[gamma-thio]triphosphate (GTP[gamma S]), significantly reduced the number of high-affinity receptors and increased the dissociation rate of 125I-Mel from its receptor. Furthermore, GTP[gamma S] treatment of ligand-receptor complexes solubilized by Triton X-100 also led to a rapid dissociation of 125I-Mel from solubilized ligand-receptor complexes. Gel filtration chromatography of solubilized ligand-receptor complexes revealed two major peaks of radio-activity corresponding to Mr greater than 400,000 and Mr ca. 110,000. This elution profile was markedly altered by pretreatment with GTP[gamma S] before solubilization; only the Mr 110,000 peak was present in GTP[gamma S]-pretreated membranes. The results strongly suggest that 125I-Mel binding sites in lizard brain are melatonin receptors, with agonist-promoted guanine nucleotide-binding protein (G protein) coupling and that the apparent molecular size of receptors uncoupled from G proteins is about 110,000.

Effect of cold shock on age-related changes in the glucose uptake of brain slices of male garden lizard.

The glucose uptake of lizard brain slices decreased between young and middle-aged groups. There was a significant increase in the parameter between the middle-aged and old-age groups. Cold shock induced a decrease in glucose uptake of brain slices in the old, with no appreciable effect in the young and middle aged.