Posteromedial Cortical Amygdaloid Nucleus Research Articles

Two Preputial Gland-Secreted Pheromones Evoke Sexually Dimorphic Neural Pathways in the Mouse Vomeronasal System.

Hexadecanol (16OH) and hexadecyl acetate (16Ac) are two pheromones secreted in a large quantity by mouse preputial glands and act on male and female mice differentially. Yet the underlying molecular and cellular mechanisms remain to be elucidated. In this study, we examined the activation of vomeronasal sensory neurons (VSNs) by these two pheromones and mapped the downstream neural circuits that process and relay their chemosignals. Using the calcium imaging method and immunohistochemistry, we found that a small number of VSNs were activated by 16OH, 16AC, or both in the male and female mice, most of which were located apically in the vomeronasal epithelium, and their numbers did not increase when the concentrations of 16OH and 16Ac were raised by 10,000-fold except that of female VSNs in response to 16OH. In the accessory olfactory bulb (AOB), the two pheromones evoked more c-Fos+ neurons in the anterior AOB (aAOB) than in the posterior AOB (pAOB); and the increases in the number of c-Fos+ neurons in both aAOB and pAOB were dose-dependent; and between sexes, the female AOB responded more strongly to 16OH than to 16Ac whereas the male AOB had the opposite response pattern. This sexual dimorphism was largely retained in the downstream brain regions, including the bed nucleus of the stria terminalis (BNST), the medial amygdaloid nucleus (MeA), the posteromedial cortical amygdaloid nucleus (PMCo), the medial preoptic area (MPA), and the ventromedial hypothalamic nucleus (VmH). Taken together, out data indicate that there is one V1r receptor each for 16OH, 16Ac, or both, and that activation of these receptors evokes sexually dimorphic neural circuits, directing different behavioral outputs and possibly modulating other pheromone-induced responses.

The time course of blood brain barrier leakage and its implications on the progression of methamphetamine-induced seizures

The initial goals of these experiments were to determine: 1) if blood-brain barrier (BBB) breakdown was a cause or an effect of METH-induced seizures; 2) all the brain regions where BBB is disrupted as seizures progress; and 3) the correlations between body temperature and vascular leakage and neurodegeneration. A fourth objective was added after initial experimentation to determine if sub-strain differences existed in adult male C57 B6 J (Jackson laboratories, JAX) versus C57 B6N (Charles River, CR) mice involving their susceptibility to BBB breakdown and seizure severity. With the 1st “maximal” intensity myoclonic-tonic seizure (MCT) varying degrees of IgG infiltration across the BBB (≤1 mm2) were prominent in olfactory system (OS) associated regions and in thalamus, hypothalamus and neocortex. IgG infiltration areas in the OS-associated regions of the bed nucleus of the stria terminalis, septum and more medial amygdala nuclei, and the hypothalamus were increased significantly by the time continuous behavioral seizures (CBS) developed. Mice receiving METH that had body temperatures of ≥40 °C had IgG infiltration along with MCT or CBS but peak body temperatures above 40 °C did not significantly increase IgG infiltration. Neurodegeneration seen at ≥6 h was restricted to the OS in both JAX and CR mice and was most prominent in the posteromedial cortical amygdaloid nucleus. Neurodegeneration in the anterior septum (tenia tecta) was seen only in the JAX mice. We hypothesize that METH-induced hypertension and hyperthermia lead to BBB breakdown and other vascular dysfunctions in the OS brain regions resulting in OS hyperexcitation. Excitation of the OS neural network then leads to the development of seizures. These seizures in turn exacerbate the energy depletions and the reactive oxygen stress produced by hyperthermia further damaging the BBB and vascular function. These events form a recurrent cycle that results in ever increasing seizure activity and neurotoxicity.

Persistent Neurological Damage Associated With Spontaneous Recurrent Seizures and Atypical Aggressive Behavior of Domoic Acid Epileptic Disease

The harmful alga Pseudo-nitzschia sp. is the cause of human amnesic shellfish poisoning and the stranding of thousands of sea lions with seizures as a hallmark symptom. A human case study and epidemiological report of hundreds of stranded sea lions found individuals presenting months after recovery with a neurological disease similar to temporal lobe epilepsy. A rat model developed to establish and better predict how epileptic disease results from domoic acid poisoning demonstrated that a single episode of status epilepticus (SE), after a latent period, leads to a progressive state of spontaneous recurrent seizure (SRS) and expression of atypical aggressive behaviors. Structural damage associated with domoic acid-induced SE is prominent in olfactory pathways. Here, we examine structural damage in seven rats that progressed to epileptic disease. Diseased animals show progressive neuronal loss in the piriform cortex and degeneration of terminal fields in these layers and the posteromedial cortical amygdaloid nucleus. Animals that display aggressive behavior had additional neuronal damage to the anterior olfactory cortex. This study provides insight into the structural basis for the progression of domoic acid epileptic disease and relates to the California sea lion, where poisoned animals progress to a disease characterized by SRS and aggressive behaviors.

Amygdaloid?Striatal Substrates Underlying Odor Hedonics and Odor-Guided Behaviors

tory tubercle by the amygdala. The olfac-tory tubercle is a striatal structure with a cortical-like organization which displays odor-evoked activity and may be criti-cal for olfactory perception (Wesson and Wilson, 2011). The anatomical findings by Novejarque et al. (2011) along with those of previous groups (Usunoff et al., 2009) suggest the involvement of the olfactory tubercle (and perhaps the tubercle’s strong connections with the basal ganglia) in the emotional regulation of olfactory percep-tion and the strong hedonic responses evoked by odors (e.g., Herz and Cupchick, 1995). Despite this, without data showing the role of the olfactory tubercle to olfactory processing, little can be inferred regarding the amygdala innervation of the olfactory tubercle.Another major contribution of the pre-sent study was the finding that all cortical amygdaloid nuclei (excluding the piri-form cortex) innervate the major island of Calleja. This was especially the case for the posteromedial cortical amygdaloid nucleus. The islands of Calleja are dense granule cell clusters residing mostly within layers II and III of the olfactory tubercle in rodents and largely in the nucleus accum-bens in humans. However, the function of the islands of Calleja is unknown. Thus while this finding by Novejarque et al. (2011) is difficult to interpret in terms of functional consequences, it is almost undoubted that the amygdala’s dense innervation of the major island of Calleja will be found important to the emotional modulation of odor perception (given their positioning within the olfactory tubercle) and to the regulation of socio-sexual behaviors.There are ample future directions to link these anatomical findings by Novejarque et al. (2011) to functional significance. First, and most recently discussed, would elimi-nation or inactivation of the major island of Calleja abolish associative changes in odor hedonics? This of course is based upon the

Vomeronasal inputs to the rodent ventral striatum

Vertebrates sense chemical signals through the olfactory and vomeronasal systems. In squamate reptiles, which possess the largest vomeronasal system of all vertebrates, the accessory olfactory bulb projects to the nucleus sphericus, which in turn projects to a portion of the ventral striatum known as olfactostriatum. Characteristically, the olfactostriatum is innervated by neuropeptide Y, tyrosine hydroxylase and serotonin immunoreactive fibers. In this study, the possibility that a structure similar to the reptilian olfactostriatum might be present in the mammalian brain has been investigated. Injections of dextran-amines have been aimed at the posteromedial cortical amygdaloid nucleus (the putative mammalian homologue of the reptilian nucleus sphericus) of rats and mice. The resulting anterograde labeling includes the olfactory tubercle, the islands of Calleja and sparse terminal fields in the shell of the nucleus accumbens and ventral pallidum. This projection has been confirmed by injections of retrograde tracers into the ventral striato-pallidum that render retrograde labeling in the posteromedial cortical amygdaloid nucleus. The analysis of the distribution of neuropeptide Y, tyrosine hydroxylase, serotonin and substance P in the ventral striato-pallidum of rats, and the anterograde tracing of the vomeronasal amygdaloid input in the same material confirm that, similar to reptiles, the ventral striatum of mammals includes a specialized vomeronasal structure (olfactory tubercle and islands of Calleja) displaying dense neuropeptide Y-, tyrosine hydroxylase- and serotonin-immunoreactive innervations. The possibility that parts of the accumbens shell and/or ventral pallidum could be included in the mammalian olfactostriatum cannot be discarded.

Efferent connections of the main olfactory bulb in the opossum ( Monodelphis domestica): A characterization of the olfactory entorhinal cortex in a marsupial

Olfactory projections have been investigated for decades, but few reports using modern, sensitive neural tracers are available. In marsupials, only lesion-degeneration studies exist and they are restricted to the genera Didelphis and Trichosurus. Some of the territories described as olfactory-recipient such as the upper portion of the rhinal fissure and the vomeronasal amygdala are, however, controversial. Also, the characterization of the olfactory portion of the entorhinal cortex is far from clear in acallosal mammals. The present report investigates, using biotinylated dextran-amine, the olfactory connections in the short-tailed opossum ( Monodelphis domestica) and characterizes the olfactory portion of the entorhinal cortex in non-placental mammals. The data indicate that olfactory projections do not reach the upper portion of the rhinal fissure, but partially end in the vomeronasal amygdala, i.e., the medial and posteromedial cortical amygdaloid nuclei; thus, although olfactory and vomeronasal system have largely segregated outputs, areas of overlap should be restudied. The olfactory portion of the entorhinal cortex is much larger than previously described, extending up to the occipital pole of the cerebral hemisphere. Collectively, these data contribute to our understanding of the organization of the hippocampal formation in marsupials.

Autoradiographic evidence that prenatal morphine exposure sex-dependently alters μ-opioid receptor densities in brain regions that are involved in the control of drug abuse and other motivated behaviors

The present study examined the effects of prenatal morphine exposure on μ-opioid receptor density in young adult male and female rats to assess the long-term alterations in several brain areas including the nucleus accumbens (NAc), bed nucleus of stria terminalis (BNST), and the basolateral (BLA), lateral (LA), central (CeA), and posteromedial cortical (PMCoA) amygdaloid nuclei. These brain areas are involved in motivating and rewarding behaviors of opiates and other drugs of abuse. The reinforcing actions of opiates appear to be μ-opioid receptor dependent. The results demonstrate that in male rats, prenatal morphine exposure significantly increases the density of μ-opioid receptors in the NAc and PMCoA. In contrast, the same prenatal morphine exposure reduces the density of μ-opioid receptors in the BLA, while increasing it in the CeA and without effects in the LA or BNST. In female rats, prenatal morphine exposure has no effects on the density of μ-opioid receptors in the above six brain areas, but the density of these receptors is dependent on the presence or absence of ovarian hormones. Thus, the present study demonstrates that mid- to late gestational morphine exposure induces long-term, sex-specific alterations in the density of μ-opioid receptors in the NAc and amygdala. Moreover, this prenatal morphine exposure also eliminates sex differences in the density of μ-opioid receptors in the NAc, CeA, and PMCoA but not in the BLA, LA, and BNST.

A spontaneous recurrent seizure-related Rattus NSF gene identified by linker capture subtraction

Spontaneous recurrent seizures (SRS) are the major clinical characteristic of epilepsy. In this study, using a SRS-behavior test combined with linker capture subtraction (LCS) to identify genes altered in their expression in response to a single kainic acid (KA)-induced SRS at 3 weeks in the rat hippocampal formation. Dot blot analysis of the differentially expressed cDNA fragments with LCS showed the down-regulation of one cDNA related to SRS, which was designated epilepsy-related gene 1 ( ERG1). Northern blot analysis showed that ERG1 mRNA was reduced by KA administration with and without SRS, but more so with SRS. This differential expression had also been confirmed by in situ hybridization, which showed that ERG1 mRNA was down-regulated in the dorsal dentate granule cells (dDGCs) of the hippocampal formation, but remarkable up-regulated in the amygdalohippocampal area (AHi), posteromedial cortical amygdaloid nucleus (PMCo) and perirhinal cortex (PRh). The complete cDNA of ERG1 was cloned, sequenced (AF142097). It encodes a Rattus homologue of N-ethylmaleimide-sensitive fusion protein (NSF), which is an ATPase that plays a key role in mediating docking and/or fusion of transport vesicles in the multi-step pathways of vesicular transport. Sequence analysis revealed that ERG1 has high sequence similarity with the cDNA of the Mus musculus suppressor of K + transport growth defect (SKD2), N-ethylmaleimide(NEM)-sensitive fusion protein of Chinese hamster and human NEM-sensitive factor (HSU03985).

Estradiol masculinizes the posteromedial cortical nucleus of the amygdala in the rat

It has been demonstrated that the posteromedial cortical amygdaloid nucleus (PMCo), is sexually dimorphic. It is shown (Experiment 1) that male orchidectomy on the day of birth (D1) decreases the volume and number of neurons of the PMCo, while a single injection of propionate testosterone to the female on D1 masculinizes the PMCo in this gender. Since male gonadectomy on D1 (Experiment 2) is counteracted by a single injection of estradiol benzoate in males it has been suggested that the masculinization of the PMCo is due to the aromatization of testosterone to estradiol in this structure. These findings support the hypothesis that the development of sex differences in structures that belong to the vomeronasal system are due to the aromatization of testosterone to estradiol shortly after birth.

Autoradiographic localization of [ 3H]nociceptin binding sites in the rat brain

The binding sites of nociceptin (also named orphanin FQ), the endogenous ligand of ORL1 (opiate receptor like 1), were localized in rat brain, using an autoradiographic procedure. High levels of binding were observed in the cingulate, retrosplenial, perirhinal, insular and occipital cortex, anterior and posteromedial cortical amygdaloid nuclei, basolateral amygdaloid nucleus, amygdaloid complex, posterior hippocampus, dorsal endopiriform, central medial thalamic, paraventricular, rhomboid thalamic, suprachiasmatic, ventromedial hypothalamic nuclei, mammillary complex, superficial gray layer of the superior colliculus, locus coeruleus, dorsal raphe nucleus. More moderate labelling was observed in the prefrontal, fronto–parietal, temporal, piriform cortex, dentate gyrus, anterior olfactory nucleus, olfactory tubercle, shell of nucleus accumbens, claustrum, lateral septum, laterodorsal thalamic, medial habenular, subthalamic, reuniens thalamic nuclei, subiculum, periaqueductal grey matter and pons. A lower binding site density was observed in the anterior and medial hippocampus, olfactory bulb, caudate putamen, the core of the nucleus accumbens, medial septum, ventrolateral, ventroposterolateral and mediodorsal thalamic nuclei, lateral and medial geniculate nuclei, hypothalamic area, substantia nigra, ventral tegmentum area and interpedoncular nucleus. A moderate and similar labelling was found in the dorsal and ventral horn of the spinal cord. No labelling was apparent in the corpus callosum. Thus, it appears that the ORL1 receptor is particularly abundant in the cerebral cortex, limbic system of the rat brain and some areas involved in pain perception.

Convergence of segregated pheromonal pathways from the accessory olfactory bulb to the cortex in the mouse.

The accessory olfactory system mediates intraspecies pheromonal communication. Two subsets of spatially segregated vomeronasal sensory neurons, presumably handling functionally and structurally different sets of ligand molecules, can be distinguished. The two subsets of sensory neurons project their axons to segregated zones of the accessory olfactory bulb (AOB) and connect with zonally separated mitral/tufted (M/T) cells, suggesting that the accessory olfactory system is divided into two distinct pathways up to the level of the AOB. To examine whether the segregation is maintained at the accessory olfactory cortical (AOC) regions, we selectively tracer-labelled mitral/tufted cells located in the rostral, caudal or in both zones of the adult mouse AOB. The results demonstrate that the axonal projection patterns of rostral zone and caudal zone M/T cells were indistinguishable in the AOC regions. Mitral/tufted cell axons from either zone of the AOB covered the entire area of all four AOC regions: the bed nucleus of the accessory olfactory tract, the medial amygdaloid nucleus, the posteromedial cortical amygdaloid nucleus and the bed nucleus of the stria terminalis. Therefore, over the entire area of each AOC region, ensembles of cortical neurons receive input from both zonal subsets of M/T cells of the AOB. However, the present results do not rule out the possibility that individual cortical neurons sample information from M/T cells of a single zone. These results are consistent with the idea that the segregation of zonal pathways collapses in the AOC regions. Clusters of cortical neurons in each AOC region may combine information from both families of pheromone receptors and thus handle signals from structurally and functionally different categories of pheromone molecules.

Female-soiled bedding induced Fos immunoreactivity in the ventral part of the premammillary nucleus (PMv) of the male mouse

Previous studies have indicated that the ventral part of the premammillary nucleus (PMv) of rodents is involved in the regulation of aggressive and male mating behavior, although the precise physiological function of the PMv is still unclear. To analyze the physiological role of the PMv in male mating behavior, the effects of exposure to bedding soiled by female mice on Fos immunoreactivity (Fos-ir), an early marker of neuronal activation, were studied in the PMv and some sex-related nuclei. We observed that exposure to female-soiled bedding induced Fos-ir expression in the PMv of the male mouse. Although Fos-ir positive cells were found in the posterodorsal part of the medial amygdaloid nucleus and in the posteromedial cortical amygdaloid nucleus, which are terminals of the neuronal projections from the main and accessory olfactory bulbs, the numbers of Fos-ir cells in those nuclei were not affected by exposure to female-soiled bedding. Moreover, Fos-ir was not detected in the ventromedial hypothalamic nucleus. It is well established that soiled bedding is useful as a source of chemosensory substances, which include “pheromones.” Thus, our findings, in agreement with previous behavioral and anatomical data, suggest that the PMv plays a role in initiating male copulative behavior that is induced by a female mice pheromone(s).

Imaging the induction and spread of seizure activity in the isolated brain of the guinea pig: the roles of GABA and glutamate receptors

1. The induction and spread of seizure activity was studied using imaging and electrophysiological techniques in the isolated whole brain of the guinea pig. We examined the role of GABA and glutamate receptor subtypes in controlling the spread of seizure activity across the olfactory cortex from a focus in the entorhinal cortex. Seizure spread was monitored by video imaging of intrinsic optical signals (reflectance changes) combined with multiple extracellular recordings. Both the unilateral and bilateral spread of seizure activity was monitored in different experiments. 2. Electrical stimulation of the lateral entorhinal cortex (10-15 V, 5 Hz, 5-10 s) evoked seizure activity that originated in the entorhinal cortex/hippocampus and later spread preferentially toward the posteromedial cortical amygdaloid nucleus ipsilaterally and bilaterally. The pattern of seizure spread in a given brain was highly reproducible. 3. The influence of gamma-aminobutyric acid (GABA) receptors on the spread of seizure activity was monitored at higher resolution on one side of the brain. Perfusion of a low concentration of the GABAA antagonist bicuculline methiodide (20 microM) resulted in spontaneous seizures that spread to the posteromedial cortical amygdaloid nucleus more rapidly than electrically evoked seizures [spread times: 5.5 +/- 3.7 s vs. 15.5 +/- 2.7 s, respectively (means +/- SE)]. Seizure spread was also more extensive in the presence of bicuculline involving the posterior perirhinal cortex and larger areas over the medial amygdala. Higher concentrations of bicuculline (100 microM) resulted in even more widespread propagation of spontaneous seizure activity throughout the olfactory cortex as well as to the perirhinal, insular, and occipital cortices. This concentration of bicuculline also further reduced the time required for seizure activity to spread from the entorhinal cortex to the posteromedial cortical amygdaloid nucleus (spread time = 2.3 +/- 1.7 s). The GABAB antagonist, CGP 35348 (200 microM), in contrast, had no significant effect of seizure induction or propagation. 4. The role of glutamate receptor subtypes in seizure propagation was studied by examining the bilateral spread of seizures. Perfusion of the kainate/alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionic acid (K/A) receptor antagonist (6-cyano-7-nitroquinoxaline-2,3-dione, CNQX, 20 microM) completely and reversibly suppressed stimulus-evoked seizure activity as detected electrophysiologically and optically. CNQX also reduced the magnitudes of field potentials recorded in the isolated brain in a reversible manner by an average of 70.8 +/- 2.21% of control. The N-methyl-D-aspartate (NMDA) receptor antagonist dibenzocyclohepteneimine (MK-801) did not significantly alter the magnitudes or shapes of field potentials recorded in the isolated brain nor did it significantly alter seizure activity measured optically or electrophysiologically. 5. Perfusion of the metabotropic glutamate receptor agonist [trans-1-amino-(IS,3R)-cyclopentanedicarboxylic acid (trans-ACPD), 150 microM] completely and reversibly suppressed stimulus-evoked seizure activity as detected electrophysiologically and optically. The magnitudes of field potentials recorded in the isolated brain also were reduced by trans-ACPD an average of 75.4 +/- 5.39% of control values. 6. These results demonstrate that GABAA-mediated transmission is functionally present and may play an important role in epileptic tissue in limiting the spread of seizure activity from the entorhinal cortex to the posteromedial cortical amygdaloid nucleus and in creating functional pathways or preferential routes of seizure spread. GABAB-mediated postsynaptic inhibition played no significant role in the induction or spread of seizure activity in this study. K/A receptors but not NMDA receptors are necessary for the induction and subsequent spread of seizure activity originating in the entorhinal cortex/hippocampus.

Embryonic and postnatal mRNA distribution of five somatostatin receptor subtypes in the rat brain

The messenger RNA (mRNA) expression of somatostatin (SRIF) receptors SSTR-1, SSTR-2, SSTR-3, SSTR-4 and SSTR-5 (called sst 1–5, now) was studied in rat brain between embryonic day 17 (E17) and post-natal day 5 (P5) by in situ hybridization histochemistry and compared to that of adult rats, sst 1 receptor mRNA expression was very low and restricted at E17, spread out at E18, to reach very high levels comparable to that of adult at P5 (e.g. in temia tecta, posteromedial cortical amygdaloid nucleus, subiculum). At E17 E18 , sst 2 receptor mRNA expression was low and limited (telencephalon); significant levels were present at P5 in allocortex, hippocampus, locus coeruleus, similarly to adult brain. sst 3 receptor mRNA was high at E17 in most brain regions, and almost as ubiquitous as in adult brain at P5. sst 4 receptor mRNA was apparently absent at E17, with low levelis in the hippocampus, amygdala and habenula at E18; a wider distribution, especially in the hippocampus and cerebral cortex was observed at P5, similar to that of adult, sst 5 receptor mRNA was not detected at E17 and negligible at E18; low levels were found in the cortex, hippocampus and cerebellum at P5. However, in adult brain, only the cerebellum and hind-brain showed some sst 5 receptor mRNA transcripts. The presence and distribution of SRIF receptor mRNAs differs substantially in embryo and adult brain. Some mRNAs are present throughout development, while others proceed only postnatally to the adult form. There are striking differences within and between the different SRIF receptor mRNAs, suggesting a role in neurogenesis for some SRIF receptors (e.g. sst 2). However, mRNA and protein levels do not necessarily correlate.

Mapping patterns of neuronal activity and seizure propagation by imaging intrinsic optical signals in the isolated whole brain of the guinea-pig

Image analysis techniques were used to examine changes in the intrinsic optical properties in the isolated brain of the guinea-pig in order to map normal neuronal activity patterns and seizure propagation in the olfactory cortex. Electrical stimulation of the lateral olfactory tract decreased light reflectance in distant cortical areas where fibres of the tract are known to project. These areas included the amygdalar, anterior and posterior piriform, and entorhinal cortices, as well as the olfactory tubercle. Stimulation of the lateral entorhinal cortex decreased reflectance in a more circumscribed area in the lateral and medial entorhinal cortex. By imaging intrinsic signals in real-time, we also demonstrated that seizure activity elicited in the entorhinal cortex/hippocampus preferentially propagated to the posteromedial cortical amygdaloid nucleus. The magnitudes of the intrinsic optical signals were correlated with the amplitudes of field potentials recorded in laminae II or III of the olfactory cortex of the same preparations. These signals had onset times of approximately 3 s during 5 Hz stimulation, consistently recovered and were graded with stimulation frequency. The generation of the intrinsic signals required postsynaptic activation, since attenuating synaptic transmission with kynurenic acid (an excitatory amino acid antagonist) eliminated the signals. The intrinsic signals exhibited maxima at 425–450, 550 and 600 nm, suggesting that they arose from changes in light absorption by cytochromes. Intrinsic signals of relatively constant magnitude were also present at 400, 475–500 and 575 nm, and at wavelengths greater than 600 nm. This suggested that an additional component of the intrinsic signal arose from changes in light scattering, possibly due to cellular swelling.

Neuropeptide Y (NPY) and peptide YY (PYY) receptors in rat brain

1. Specific binding sites for neuropeptide Y (NPY) and peptide YY (PYY) were investigated in rat brain areas using quantitative receptor autoradiography with 125I-Bolton-Hunter NPY (125I-BH-NPY) and 125I-PYY, radioligands for PP-fold family peptides receptors. 2. There were no differences between localization of 125I-BH-NPY and 125I-PYY binding sites in the rat brain. High densities of the binding sites were present in the anterior olfactory nucleus, lateral septal nucleus, stratum radiatum of the hippocampus, posteromedial cortical amygdaloid nucleus, and area postrema. 3. In cold ligand-saturation experiments done in the presence of increasing concentrations of unlabeled NPY and PYY, 125I-BH-NPY and 125I-PYY binding to the stratum radiatum of the hippocampus, layer I of the somatosensory frontoparietal cortex, molecular layer of the cerebellum, and area postrema was single and of a high affinity. There was a significant difference between the affinities of 125I-BH-NPY (Kd = 0.96 nM) and 125I-PYY binding (Kd = 0.05 nM) to the molecular layer of the cerebellum. The binding of the two radioligands to the other areas examined had the same affinities. 4. When comparing the potency of unlabeled rat pancreatic polypeptide (rPP), a family peptide of NPY and PYY, to inhibit the binding to the areas examined, rPP displaced 125I-BH-NPY and 125I-PYY binding to the area postrema more potently than it did the binding to the stratum radiatum of the hippocampus, layer I of the somatosensory frontoparietal cortex, and molecular layer of the cerebellum. 5. Thus, the quantitative receptor autoradiographic method with 125I-BH-NPY and 125I-PYY revealed differences in binding characteristics of specific NPY and PYY binding sites in different areas of the rat brain. The results provide further evidence for the existence of multiple NPY-PYY receptors in the central nervous system.

Chronic testosterone propionate treatment decreases the concentration of [ 3H]quipazine binding at 5-HT 3 receptors in the amygdala of the castrated male rat

Chronic administration of testosterone propionate (TP) was found to decrease the concentration of [ 3H]quipazine binding at 5-HT 3 receptors in the lateral and basal amygdaloid nuclei of the brains of castrated male rats. TP had no effect on the binding of [ 3H]quipazine at 5-HT 3 receptors in the posterolateral or posteromedial cortical amygdaloid nuclei, or in the amygdalohippocampal areas. It is suggested that the effects of testosterone on sexual and other social behaviors in male rats may be mediated, at least in part, by decreases in the activation of 5-HT 3 receptors in the amygdala.

Participation of the olfactory system in the control of approach behavior of the female rat to the male

The amounts of time spent by females in the sector of an open field close to the cage housing a normal male or a castrated male were measured in order to quantitate the tendency of the female to reach physical proximity to a sexually active male (androtropism). Intact proestrous or ovariectomized females primed with 100 μg of estradiol benzoate/kg b.wt. (EB) or EB plus 2 mg progesterone/kg b.wt. (P) spent significantly more time close to the sexually active (intact) male than in the proximity of the orchidectomized male. In order to determine whether olfactory clues were sufficient for female rats to distinguish between intact and castrated males, the males were removed from the stimulus cages, leaving the soiled bedding in place. Ovariectomized rats primed with EB or EB plus P clearly preferred proximity to the cage where the intact male had been living. No preference was evident after transection of olfactory nerves in proestrous rats or in ovariectomized rats primed with EB plus P. Resection of the vomeronasal organ also suppressed preference. These results indicate that olfactory input is necessary and sufficient for androtropism to occur, and suggest that the accesory olfactory system is involved in the analysis of olfactory signals used by female rats to identify the endocrine status of prospective sexual partners. In a different group of animals, it was demonstrated that destruction of the posteromedial cortical amygdaloid nucleus also suppressed preference for the intact male. It is proposed that this structure serves as a relay station for the analysis and integration of olfactory input significant for the motivational control of sexual behavior in the female rat. None of the lesions affected either exploratory activity or sexual receptivity measured as the lordosis score to ten mounts by active males.

Improved quantitative radioautography of rat brain δ-opioid binding sites using [3H]DSTBULET, a new highly potent and selective linear enkephalin analogue

The binding properties of [(3)H]DSTBULET, a new potent and specific ligand for ?-opioid binding sites, were characterized using slices from rat brain striatum. Specific [(3)H]DSTBULET binding reached steady-state within 60 min at 20 degrees C, was saturable and reversible and the ligand appeared to interact with a single class of binding sites, characterized as ? by competition experiments. Scatchard analysis of the saturation isotherm plots yielded a K(D) value of 5.73 nM. At this concentration the specific binding was 94% of the total binding. Unlabeled DSTBULET had a low affinity (K(1) = 422 nM) for ? binding sites labeled by [(3)H]DAGO and at 5 nM [(3)H]DSTBULET interacted with a maximum of 1.2% of total ? sites. [(3)H]DSTBULET was therefore used for a detailed quantitative radioautographic analysis of the distribution of rat brain ?-opioid binding sites in order to clarify some inconsistencies in the relative densities of these sites previously reported using either various non specific ligands or [(3)H]DPDPE, a cyclic enkephalin endowed with high ? selectivity but relatively low affinity. In addition to the claustrum, basolateral and posteromedial cortical amygdaloid nuclei, nucleus accumbens ahd caudate putamen, regions well-known to contain very high levels of ? sites, a [(3)H]DSTBULET labeling was also found in the intermediodorsal, rhomboid and mediodorsal (lat.) thalamic nuclei, cortex frontoparietal (layers II + III and V + VI), ventroposterior (parvocellular) and reuniens thalamic nuclei, and anterior olfactory nucleus (posterior part). In the thalamus, the mediodorsal, central medial and centrolateral nuclei and the posterior thalamic nucleus group were moderately labeled. The superior colliculus (superficial gray layer), the interpeduncular nucleus, the stria terminalis and the nucleus solitary tractus were moderately labeled. Lower labeling was found in the medial habenula, ventromedial, laterodorsal and ventroposterior (median) thalamic nuclei, dentate gyrus and the pyramidal cell layer of the hippocampus. In the globus pallidus, ventromedial hypothalamic nucleus, ventroposterior (lateralis) thalamic nucleus, substantia nigra, ventral tegmental area, periaqueductal gray matter and dorsal raphe the labeling was scarce but significant. At all levels in the spinal cord, a low labeling was found, restricted to the substantia gelatinosa. Interestingly ?-opioid receptors are highly concentrated in the more recently developed areas of the brain (cortex, neostriatum), where they could be involved in modulation of integrational processes mainly through regulation of aminergic (especially dopamine) pathways. Therefore, owing to its high affinity and good selectivity, [(3)H]DSTBULET seems to be the most appropriate radiolabeled probe currently available to investigate the ?-opioid receptors and to quantify these binding sites by radioautography with a high sensitivity and accuracy. Accordingly, labeling was found in several areas (ventral tegmental area, substantia nigra, nucleus tractus solitarius) where a mismatch between the site of action of ?-opioids and the presence of ? sites has been previously hypothesized.

Anterograde transsynaptic transport of WGA-HRP in rat olfactory pathways

The transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) was studied in rat olfactory pathways. After applications of tracer to the vomeronasal organ, the olfactory epithelium or injections into the olfactory bulb, WGA-HRP reaction product was observed in second-order neuron terminal areas of each pathway, e.g. within posteromedial cortical amygdaloid nucleus, primary olfactory cortex and contralateral primary olfactory cortex, respectively. The results indicate that anterograde transsynaptic transport of WGA-HRP occurs in olfactory pathways, as has been shown in visual, somatosensory and limbic systems, and thus, anterograde transsynaptic transport may be a mechanism for neurons to exchange materials and/or messages.