Central Amygdaloid Nucleus Research Articles

The nigro-striatal and nigro-amygdaloid pathways undergo different degeneration processes in brains of dementia with Lewy bodies

We immunohistochemically investigated the degeneration processes of the nigro-striatal and nigro-amygdaloid pathways and the relationship between the loss of dopaminergic neurons and Lewy bodies (LB) formation in the substantia nigra using 15 autopsied cases of dementia with Lewy bodies (DLB). The number of tyrosine hydroxylase (TH)-positive neurons in the substantia nigra and TH-positive axonal terminals in the putamen decreased with a specific pattern. The substantia nigra possesed α-synuclein-positive LB-bearing neurons that were almost evenly distributed, while the putamen exhibited diffuse or granular α-synuclein-immunostaining. Most of the granular stains were positive for anti-phosphorylated α-synuclein antibody, whereas the diffuse stains were negative. These findings suggest that the axonal terminals in the putamen undergo abnormal α-synuclein accumulation, but may not always originate from LB-bearing neurons in the substantia nigra. The central amygdaloid nucleus contained anti-α-synuclein- and -phosphorylated α-synuclein-positive dystrophic axonal terminals, the degree of which was greater for cases with granular staining in the putamen, and which was proportional to the number of α-synuclein-positive neurons in the substantia nigra. Thus, the axonal terminals in the central amygdaloid nucleus may have originated from LB-bearing neurons in the substantia nigra. The results of the present study indicate that the nigro-striatal and nigro-amygdaloid pathways undergo different degeneration processes in DLB, and suggest that the degeneration of the nigro-amygdaloid pathway more strongly reflects LB formation in dopaminergic neurons of the substantia nigra than that of the nigro-striatal pathway. In addition, they indicate that there is no direct relationship between the loss of dopaminergic neurons and LB formation in the substantia nigra.

Repeated cocaine exposure during adolescence alters glutamic acid decarboxylase-65 (GAD 65) immunoreactivity in hamster brain: correlation with offensive aggression

Male Syrian hamsters ( Mesocricetus auratus) treated with low-dose (0.5 mg/kg/day) cocaine throughout adolescence (P27–P56) display highly escalated offensive aggression. The current study examined whether adolescent cocaine exposure influenced the immunohistochemical localization of glutamic acid decarboxylase-65 (GAD 65), the rate-limiting enzyme in the synthesis of γ-aminobutyric acid (GABA), a fast-acting neurotransmitter implicated in the modulation of aggression in various species and models of aggression. Hamsters were administered low doses of cocaine throughout adolescence, scored for offensive aggression using the resident–intruder paradigm, and then examined for changes in GAD 65 immunoreactivity in areas of the brain implicated in aggression control. When compared with saline-treated control animals, aggressive cocaine-treated hamsters showed significant differences in the area covered by GAD 65 puncta in several notable aggression regions, including the anterior hypothalamus, the medial and central amygdaloid nuclei, and the lateral septum. However, no differences in GAD 65 puncta were found in other aggression areas, such as the bed nucleus of the stria terminalis, the ventrolateral hypothalamus, and the corticomedial amygdala. Together, these results suggest that altered GABA synthesis and function in specific aggression areas may be involved in adolescent cocaine-facilitated offensive aggression.

G protein-coupled galanin receptor distribution in the rat central nervous system

The action of galanin in the central nervous system is mediated by at least three galanin receptor subtypes (GalR1, GalR2 and GalR3) which belong to the family of G protein-coupled receptors. GalR1 and GalR2 are coupled to G(i/o) proteins, although the latter may also be coupled to G(q/11) proteins. The aim of the present study was to identify the anatomical distribution and quantify the density of GalRs coupled to G proteins. The galanin (10(-6) M) stimulated guanosine 5'-(gamma-[35S] thio)triphosphate binding assay was used in tissue sections from the rat brain. Maximal percentages of stimulation over basal levels were found in the anterior olfactory nucleus and in the lateral olfactory tract nucleus ( approximately 54%). High levels of stimulation were recorded in diverse hypothalamic nuclei (16-28%), in the amygdala (central amygdaloid nucleus, 40%), in the spinal trigeminal tract (23%) and in layers 1-2 of the spinal cord (26%). Moderate binding stimulation (5-13%) was observed in thalamus, substantia nigra pars compacta, parabrachial nucleus, locus coeruleus and dorsal raphe nucleus. The lowest stimulation induced by galanin was recorded in diverse areas of the cortex, striatum, hippocampus and substantia nigra pars reticulata. The results show an anatomical distribution similar to that described for GalR1. However, in diverse brain areas, in which a high density of these receptors has previously been reported, only a moderate coupling to G proteins was found. These findings would suggest that the efficacy of galanin to induce an effective coupling of its receptors to G proteins could be different depending on the brain area.

Chronic restraint stress down-regulates amygdaloid expression of polysialylated neural cell adhesion molecule

The amygdala is a brain area which plays a decisive role in fear and anxiety. Since exposure to chronic stress can induce profound effects in emotion and cognition, plasticity in specific amygdaloid nuclei in response to prior stress has been hypothesized to account for stress-induced emotional alterations. In order to identify amygdala nuclei which may be affected under chronic stress conditions we evaluated the effects of 21-days chronic restraint stress on the expression of a molecule implicated crucially in alterations in structural plasticity: the polysialylated neural cell adhesion molecule. We found that polysialylated neural cell adhesion molecule-immunoreactivity within the amygdala, present in somata and neuronal processes, has a regional gradient with the central medial and medial amygdaloid nuclei showing the highest levels. Our results demonstrate that chronic restraint stress induced an overall reduction in polysialylated neural cell adhesion molecule-immunoreactivity in the amygdaloid complex, mainly due to a significant decrease in the central medial amygdaloid and medial amygdaloid nuclei. Our data suggest that polysialylated neural cell adhesion molecule in these nuclei may play a prominent role in functional and structural remodeling induced by stress, being a potential mechanism for cognitive and emotional modulation. Furthermore, these finding provide the first clear evidence that life experiences can regulate the expression of polysialylated neural cell adhesion molecule in the amygdaloid complex.

Y1-receptors regulate the expression of Y2-receptors in distinct mouse forebrain areas

Y-receptor-knockout mice have become an important tool to elucidate specific physiological roles of individual Y-receptors. However, their phenotypes are not always confirmatory to results obtained by pharmacological investigations in vivo or in vitro. These discrepancies may, at least in part, be due to compensatory changes in the expression of remaining Y-receptor types. To determine whether deletion of individual Y-receptors results in altered mRNA expression and/or binding toward other Y-receptor types, we applied in-situ hybridization and radioligand-binding studies on brain slices of Npy1r-, Npy2r- or Npy5r-knockout mice. Significant changes were seen in Y1-receptor-deficient mice. Thus, Y2-receptor mRNA and 125I-peptide YY 3-36 binding in the hippocampus proper were increased by up to 55% and 89%, respectively. Similar increases in 125I-peptide YY 3-36 binding were observed in the caudo-dorsal extension of the lateral septum, an area heavily targeted by hippocampal projections and involved in Y1-receptor-regulated anxiety. Increased 125I-peptide YY 3-36 binding and Y2-receptor mRNA levels were also observed in the medial amygdaloid nucleus. In contrast, 125I-peptide YY 3-36 binding was reduced in the central amygdaloid nucleus. Y2-receptor mRNA in the intermediate part of the lateral septum was reduced by 42%. Only minimal changes were observed in Y2- or Y5-receptor-deficient mice. Our results demonstrate that compensatory changes in the expression of Y2-receptors occur in Y1-receptor-deficient mice. These adaptations are likely to contribute to changed physiological function. Thus, alterations in Y2-receptors have to be taken in account upon discussion of Y1-receptor function, especially in emotional aspects like anxiety and aggression, but also alcoholism.

Immunohistochemical localization of gastrin-releasing peptide receptor in the mouse brain

Gastrin-releasing peptide (GRP) is a mammalian bombesin (BN)-like peptide that binds with high affinity to the GRP receptor (GRP-R). Previous behavioral studies using mice and rats showed that the GRP/GRP-R system mediates learning and memory by modulating neurotransmitter release in the local GABAergic network of the amygdala and the nucleus tractus solitarius (NTS). To date, the precise distribution of GRP-R in the brain has not been elucidated. We used a synthetic peptide derived from mouse GRP-R to generate affinity-purified antibodies to GRP-R and used immunohistochemistry to determine the distribution of GRP-R in the mouse brain. The specificity of anti-GRP-R antibody was confirmed in vitro using COS-7 cells transiently expressing GRP-R and in vivo using GRP-R-deficient and wild-type mouse brain sections. GRP-R immunoreactivity was widely distributed in the isocortex, hippocampal formation, piriform cortex, amygdala, hypothalamus, and brain stem. In particular, GRP-R immunoreactivity was observed in the lateral (LA), central, and basolateral amygdaloid (BLA) nuclei and NTS, which are important regions for memory performance. Double-labeling immunohistochemistry demonstrated that subpopulations of GRP-R are present in GABAergic neurons in the amygdala. Consequently, GRP-R immunoreactivity was observed in the GABAergic neurons of the limbic region. These anatomical results provide support for the idea that the GRP/GRP-R system mediates memory performance by modulating neurotransmitter release in the local GABAergic network.

Oxytocin-induced excitation of neurones in the rat central and medial amygdaloid nuclei

Central oxytocin plays an important role in regulating emotionality. The amygdala expresses gonadal steroid-sensitive oxytocin binding sites in both the central and medial sub-nuclei, although the densities markedly differ between these nuclei. These studies examined the in vitro electrophysiological effects of oxytocin in the two amygdaloid nuclei and compared responses in female rats in different reproductive states (virgin, pregnant and lactating). Oxytocin (10 −9–10 −6M) caused a concentration-dependent increase in the firing rate of 20–36% of the neurones in both nuclei. Although autoradiographic studies using the oxytocin receptor antagonist [ 125I] d(CH 2) 5[Tyr(Me) 2,Thr 4,Orn 8,Tyr-NH 2 9]-vasotocin showed a higher density of binding in the central nucleus of the amygdala than medial nucleus of the amygdala, neurones in the central nucleus of the amygdala had a much lower sensitivity to oxytocin: equivalent responses obtained with 10 −6M in the central nucleus of the amygdala and 10 −8M in the medial nucleus of the amygdala, and neurones in the central nucleus of the amygdala were insensitive to concentrations below 10 −6M. Furthermore, repeated applications of oxytocin induced homologous desensitization in the central nucleus of the amygdala, but not medial nucleus of the amygdala—a single application of oxytocin producing long duration suppression of responses. This indicates that oxytocin has contrasting modes of action in the amygdala. Studies made across the reproductive cycle showed that lactating animals exhibited a larger proportion of oxytocin-responsive neurones in the medial nucleus of the amygdala and a smaller proportion in the central nucleus of the amygdala, compared with virgin or pregnant animals, indicating a peripartum shift in relative activation within the amygdala. However, changes in responses were not accompanied by changes in the density of oxytocin binding sites. These data show that oxytocin has a markedly different efficacy on neuronal activation in the central and medial sub-nuclei of the amygdala. The relative shift in excitatory responses between these two nuclei may underlie some of the neuroendocrine, behavioral and anxiolytic effects which have been ascribed to oxytocin in the periparturient rat.

The Corticotropin-Releasing Factor (CRF)-system and monoaminergic afferents in the central amygdala: Investigations in different mouse strains and comparison with the rat

Corticotropin-releasing-factor (CRF) containing systems and monoaminergic afferents of the central amygdaloid nucleus (Ce) are crucial players in central nervous stress responses. For functional analyses of specific roles of these systems, numerous mouse models have been generated which lack or overexpress individual signal transduction components. Since data concerning system morphologies in murine brain are rarely available, mouse studies are usually designed and interpreted based on previous findings in rats, although interspecies differences are frequent. In the present study, in situ hybridization for CRF mRNA and correlative immunocytochemistry for CRF and monoaminergic afferents revealed numerous CRF mRNA-reactive neurons in the lateral Ce subnucleus (CeL) codistributed with dense dopaminergic fiber plexus in mice as has been demonstrated in rats. However, while in rats the lateral capsular Ce (CeLc) displays only scarce CRF immunoreactive (CRF-ir) innervation, particularly dense CRF-ir fiber plexus were observed in the CeLc in mice, with differences in labeling densities between different strains. CRF-ir terminal fibers overlap with the moderate serotonergic innervation of this subnucleus in mice. Additionally, CRF mRNA-reactive neurons were found immediately dorsal to the amygdala in the region of the interstitial nucleus of the posterior limb of the anterior commissure/amygdalostriatal transition area in both species. In mice, this region displayed dense CRF-ir fiber plexus, with variations between the strains. The results indicate that in mice and rats dopaminergic afferents represent the primary monoaminergic input to the CRF neurons in the CeL. In mice only, CRF-ir afferents provide dense innervation of CeLc neurons. Since the CeLc lacks dopaminergic input in both species but possesses moderate serotonergic afferents, CRF/serotonin interactions may occur selectively in mouse CeLc. The observed interspecies and interstrain differences in CRF input and CRF/monoaminergic interactions may influence the interpretation of findings concerning Ce functions in stress and fear in mouse models.

Immunohistological characterization of striatal and amygdalar structures in the telencephalon of the fire-bellied toad bombina orientalis

The subpallium of the fire-bellied toad Bombina orientalis was studied by means of enzyme-histological detection of NADPH-diaphorase and immunohistological demonstration of aspartate, GABA, calretinin, choline-acetyl transferase, Leu-and Met-enkephalin, neuropeptide Y, 5-hydroxy-tryptamine (serotonin), somatostatin, substance P and tyrosine-hydroxylase. As in other vertebrates, the striato-pallidum is characterized by GABA-, substance P- and enkephalin-immunoreactivity. Neurons and fibers differing in immunoreactivity are arranged in layers. Choline-acetyl transferase-immunoreactive neurons were found in a position corresponding to the mammalian cholinergic cell-group (Ch4-group), which therefore may be homologous to the nucleus basalis of Meynert. Within the amygdaloid complex, the cortical and lateral (vomeronasal) nuclei are similar in calretinin-, GABA-, NADPH-diaphorase-, enkephalin, substance P- and neuropeptide Y-(immuno)histology. The medial and central amygdaloid nuclei reveal a dense peptidergic innervation, and the medial amygdala additionally exhibits serotonergic fibers and cell bodies staining for neuropeptides and tyrosine-hydroxylase. Differences between Bombina and other anuran species exist, such as the absence of cholinergic neurons in the striatum. Our findings corroborate the view based on recent studies on the hodology and cytoarchitecture of the anuran telencephalon that the anuran ventral telencephalon contains most of the structures found in the mammalian brain. This concerns a septal region, a dorsal and ventral striato-pallidum including a nucleus accumbens and an amygdaloid complex consisting of a central, cortical and vomeronasal amygdala. The only major difference appears to concern the lack of a basolateral amygdala.

Anxiolytic effects of intra-amygdaloid injection of the D1 antagonist SCH23390 in the rat

The intercalated islands are intra-amigdaloid clusters of D1 receptor rich GABAergic neurons, which control impulse traffic between the basolateral complex and the central nucleus of the amygdala. As dopaminergic transmission within the amygdala may play a role in anxiety, the effect of the D1 antagonist SCH23390 microinjected mainly close to the rostral intercalated islands in rats was studied, using the White and Black Box test. SCH23390 reduced anxiety by an increase in the latency of the first entry into the black compartment and by an increase in the total time spent in the white compartment of the White and Black Box test, while there was no significant modification of locomotion. It is suggested that blockade of D1 receptors in the rostral intercalated islands may reduce anxiety through a reduction of GABA-mediated dishinibition of the central amygdaloid nucleus.

Brief exposure to predator odor and resultant anxiety enhances mesocorticolimbic activity and enkephalin expression in CD‐1 mice

The present study assessed alterations in mesolimbic enkephalin (ENK) mRNA levels after predator [2,5-dihydro-2,4,5-trimethylethiazoline (TMT)] and non-predator (butyric acid) odor encounter and/or light-dark (LD) testing in CD-1 mice immediately, 24, 48 and 168 h after the initial odor encounter and/or LD testing. The nucleus accumbens, ventral tegmental area, basolateral (BLA), central (CEA) and medial amygdaloid nuclei, prelimbic and infralimbic cortex were assessed for fos-related antigen (FRA) and/or ENK mRNA as well as neuronal activation of ENK neurons (FRA/ENK). Mice exposed to TMT displayed enhanced freezing and spent less time in the light of the immediate LD test relative to saline- or butyric acid-treated mice. Among mice exposed to TMT, LD anxiety-like behavior was associated with increased FRA in the prelimbic cortex and accumbal shell and decreased ENK-positive neurons in the accumbal core. Mice displaying high TMT-induced LD anxiety exhibited increased ENK-positive neurons in the BLA, CEA and medial amygdaloid nuclei relative to mice that displayed low anxiety-like behavior in the LD test after TMT exposure. In the BLA and CEA, 'high-anxiety' mice also displayed increased FRA/ENK after TMT exposure and LD testing. In contrast to neural cell counts, the level of ENK transcript was decreased in the BLA and CEA of 'high-anxiety' mice after TMT exposure and LD testing. These data suggest that increased FRA may regulate stressor-responsive genes and mediate long-term behavioral changes. Indeed, increased ENK availability in mesolimbic sites may promote behavioral responses that detract from the aversiveness of the stressor experience.

Microinjection of bicuculline into the central nucleus of the amygdala alters gustatory responses of the rat parabrachial nucleus

The central amygdaloid nucleus (CeA) receives projection from the parabrachial nucleus (PBN) gustatory neurons and descendingly projects to the PBN, and taste responses in the PBN are significantly affected by stimulation or lesion of the CeA. To examine whether the GABA receptors within the CeA are involved in this modulation, the effects of microinjection of bicuculline, a GABA A-selective antagonist, into the CeA on the activities of PBN taste neurons were observed by using extracellular recording technique. In general, after bicuculline was administered to ipsilateral CeA, the responses of PBN neurons to four tastants all increased, with the magnitudes significantly higher than those obtained before drug administration ( P<0.01), respectively. However, after bicuculline was delivered into the contralateral CeA, only the responses to NaCl, HCl and QHCl increased. According to the best-stimulus category, 47% NaCl-best (8/17), 64% HCl-best (7/11), 80% QHCl-best (4/5), and 33% sucrose-best (1/3) increased their responses to at least one basic taste stimulus after GABA A receptors within the ipsilateral CeA were blocked. After contralteral CeA injection, more NaCl-best neurons (6/8) increased responses than that after ipsilateral CeA injection, but other best-stimulus units showed no differences before and after drug injection into the contralateral CeA. Analyses of across-unit patterns indicated that the correlation coefficient of responses between NaCl and sucrose was apparently higher after drug administration to the CeA. However, after drug injection into the contralateral CeA, the correlations between NaCl and the other three tastants were higher than those before. These results indicate that the GABA A receptors within the CeA play an important role in modulating the gustatory activities of PBN neurons.

C-Fos Expression in the Rat Cerebral Cortex during Systemic GvH Reaction

Objective: It is becoming clear that the CNS receives signals from the peripheral immune system. In order to identify the areas of the brain that receive information about a specific immune response to allogeneic antigens, we studied the expression of c-Fos, a neural activation marker, in the cerebral cortex following the induction of a graft-vs.-host reaction (GvHR) in rats. Methods: C-Fos expression in the brain was studied by immunohistochemistry. GvHR was induced in (WKY × PVG)F₁ rats by injecting 5 × 10⁸ spleen cells from PVG rats. Control rats received syngeneic cells. Results: No c-Fos immunoreactivity (IR) was observed in animals undergoing GvHR in the nucleus tractus solitarii (NTS), the locus coeruleus (LC), the organum vasculosum of lamina terminalis (OVLT), the paraventricular nucleus (PVN) or the central amygdaloid nucleus (Ce). In contrast, 3 days after GvH induction c-Fos IR was observed in the piriform cortex and several other olfactory-related regions indicating the stimulation of the olfactory pathway during GvHR. Strong c-Fos IR was also observed in the occipital visual cortex of animals undergoing a GvHR, suggesting that GvHR can affect visual functions. In addition, GvHR induced c-Fos IR in the prefrontal cortex (Cg3, orbital cortex), a region that has interconnections with most sensory modalities. Double-staining studies indicate that the cells that express the c-Fos signal are neurons. Conclusion: We have defined the distribution of brain neurons that are affected during the induction phase of GvHR. Our results also indicate that the integration and processing of information from the immune system at CNS levels involve different areas during different types of immune responses.

Fos expression in the rat brain after intraperitoneal injection of Staphylococcus enterotoxin B and the effect of vagotomy.

The current study was designed to locate the neuronal activation in rat brain following intraperitoneal injection of Staphylococcus enterotoxin B (SEB) and observe the consequence of preliminary subdiaphragmatic vagotomy on SEB-induced brain Fos expression to clarify the role of the vagus nerve in sensation and transmission of abdominal SEB stimulation. The results showed that intraperitoneal SEB (1 mg/kg) induced a robust Fos expression in widespread brain areas. A significant increase of Fos immunoreactive cells were observed in the solitary tract nucleus, locus ceruleus, lateral parabrachial nucleus, ventrolateral part of central gray, medial amygdaloid nucleus, central amygdaloid nucleus, ventromedial part of thalamus, dorsomedial part of thalamus, hypothalamic paraventricular nucleus, lateral habenula, and lateral septum nucleus following SEB challenge. In hypothalamic paraventricular nucleus, in addition to the dense Fos expression in the parvocellular portion, some Fos-positive cells were also observed in the anterior magnocellular nucleus of the complex. Double immunofluorescence studies showed that these Fos-immunoreactive cells were mostly oxytocinergic. The results also showed that subdiaphragmatic vagotomy largely attenuated, but not totally abrogated, the brain Fos expression induced by abdominal administration of SEB. Our data suggest that peripheral SEB stimulation can induce activation of neurons in widespread brain areas and that the vagus plays a crucial role in transmitting the signal of abdominal immune stimulation to the brain.

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Projections from the thalamic gustatory nucleus, i.e. the parvicellular part of the posteromedial ventral thalamic nucleus (VPMpc) to the forebrain regions were studied in the rat by the tract-tracing methods with anterograde tracer (biotinylated dextran amine, BDA) and anterograde/retrograde tracer (wheat-germ agglutinin-horseradish peroxidase, WGA-HRP). After BDA injection into the VPMpc, terminal labeling was observed in the insular cortex, amygdaloid complex, and fundus striati. The terminal labeling in the amygdaloid complex was distributed in dorsolateral area of the rostral part of the lateral amygdaloid nucleus and the rostral part of the lateral subdivision of the central amygdaloid nucleus. The terminal labeling in the central amygdaloid nucleus extended to the fundus striati. The retrograde tracing study with WGA-HRP revealed that the projection fibers from the VPMpc to the amygdaloid complex originated from the medial part of the VPMpc and also from the thalamic area medial to the VPMpc. In the rats injected with Fluoro-Gold and WGA-HRP, respectively into the insular cortex and amygdaloid complex, no double-labeled neuronal cell bodies were found in the VPMpc, although neurons labeled singly with Fluoro-Gold were intermingled with those singly labeled with WGA-HRP in the medial part of the VPMpc. The results indicated that VPMpc neurons projecting to the amygdaloid complex constituted a population different from VPMpc neurons projecting to the insular cortex.

Increased dopamine release in vivo by estradiol benzoate from the central amygdaloid nucleus of Parkinson's disease model rats.

In addition to the dopaminergic neurons in the nigrostriatal system, the properties of dopaminergic neurons in the mesolimbic system, such as the amygdala, are also of interest and importance because of their specific neuromodulatory effects in the pathophysiology of Parkinson's disease (PD). Using the fast cyclic voltammetry (FCV) technique, we present evidence to indicate that electrically-evoked dopamine (DA) release from the amygdala, especially the central amygdaloid nucleus (CAN), of ovariectomized (OVX) female rats was significantly enhanced with increasing doses of estradiol benzoate (EB; 30, 50 and 100 microg/kg). Impaired DA release from the amygdala of an OVX rat PD model can also be increased by EB treatment (50 microg/kg) to a level similar to that of controls. The well established neuroprotective effects of estrogen may be beneficial for reducing the dysfunction of dopaminergic neurons in mesolimbic structures of rat PD models and PD patients.

Species differences in brain pre-pro-neurotensin/neuromedin N mRNA distribution: the expression pattern in mice resembles more closely that of primates than rats

We have used in situ hybridization to determine the distribution of pre-pro-neurotensin/neuromedin N (NT/N) mRNA in the brain of mice and rats. In rats and mice, expression was observed in the lateral septal nucleus, nucleus accumbens, medial preoptic area, bed nucleus of the stria terminalis, lateral hypothalamus, central amygdaloid nucleus and the subicilum. However, several differences in the NT/N mRNA distribution were observed between rats and mice in other brain areas. In mice, NT/N expression was detected in the subthalamic nucleus and geniculate nucleus, whereas expression was not observed in these brain areas in rats. Surprisingly, expression was not observed in mouse mesencephalic dopaminergic (mesDA) neurons and the CA1 area of the hippocampus, areas known to contain NT/N mRNA in the rat brain. Taken together, these results show that although the brain NT/N mRNA distribution largely overlaps in mice and rats, species differences exist in specific brain areas in rodents. Moreover, these data indicate that the distribution in mice resembles most that of primates than rats.

Region-specific onset of handling-induced changes in corticotropin-releasing factor and glucocorticoid receptor expression.

Early-life experience including maternal care profoundly influences hormonal stress responses during adulthood. Daily handling on postnatal day (P) 2-9, eliciting augmented maternal care upon returning pups to their cage, permanently modifies the expression of the stress neuromodulators corticotropin-releasing factor (CRF) and glucocorticoid receptor (GR). We have previously demonstrated reduced hypothalamic CRF expression already at the end of the handling period, followed by enhanced hippocampal GR mRNA levels (by P45). However, the initial site(s) and time of onset of these enduring changes have remained unclear. Therefore, we used semiquantitative in situ hybridization to delineate the spatiotemporal evolution of CRF and GR expression throughout stress-regulatory brain regions in handled (compared with undisturbed) pups. Enhanced CRF mRNA expression was apparent in the amygdaloid central nucleus (ACe) of handled pups already by P6. By P9, the augmented CRF mRNA levels persisted in ACe, accompanied by increased peptide expression in the bed nucleus of the stria terminalis and reduced expression in the paraventricular nucleus. The earliest change in GR consisted of reduced expression in the ACe of handled pups on P9, a time point when hippocampal GR expression was not yet affected. Thus, altered gene expression in ACe, bed nucleus of the stria terminalis as well as paraventricular nucleus may contribute to the molecular cascade by which handling (and increased maternal care) influences the stress response long term.

Spontaneous cannabinoid withdrawal produces a differential time-related responsiveness in cannabinoid CB1 receptor gene expression in the mouse brain.

This study aimed to examine the behavioural and neurochemical (cannabinoid CB1 receptor gene expression) changes induced by spontaneous cannabinoid withdrawal in mice. Tolerance was assessed by measuring rectal temperature and motor activity in the open-field test after CP-55, 940 administration. Cannabinoid withdrawal symptoms were determined by measuring motor activity and behavioural signs of abstinence. Cessation of CP-55, 940 treatment in tolerant mice induced a spontaneous time-dependent behavioural withdrawal syndrome consisting of marked increases (140%) in motor activity, number of rearings (170%), decreases in grooming (57%), wet dog shakes (73%) and rubbing behaviours (74%) on day 1, progressively reaching values similar to vehicle-treated mice on day 3. Interestingly, this spontaneous cannabinoid withdrawal resulted in CB1 gene expression upregulation (20-30%) in caudate-putamen, ventromedial hypothalamic nucleus, central amygdaloid nucleus and CA1, whereas in the CA3 field of hippocampus, a significant decrease (15-20%) was detected. Taken together, the results of this study suggest that cessation of CP-55, 940 administration in tolerant mice produces a behavioural cannabinoid withdrawal syndrome and a selective and differential responsiveness in CB1 receptor gene expression in several brain regions of the mice. These findings further suggest a time and regional differential role for cannabinoid receptors in short- and long-term neuroadaptations that occur after exposure to cannabis derivatives.

Centrally administered orexin-A activates corticotropin-releasing factor-containing neurons in the hypothalamic paraventricular nucleus and central amygdaloid nucleus of rats: possible involvement of central orexins on stress-activated central CRF neurons

We examined the effects of centrally administered orexin-A on corticotropin-releasing factor (CRF)-containing neurons in the hypothalamic paraventricular nucleus (PVN) and the central amygdaloid nucleus (CeA) of rats, using dual immunostaining for CRF and Fos. Ninety minutes after intracerebroventricular administration of orexin-A, approximately 96% and 45% of CRF-containing neurons expressed Fos-like immunoreactivity (LI) in the PVN and the CeA, respectively. We also examined the effects of immobilized stress and cold exposure on orexin-A-containing neurons in the rat hypothalamus using dual immunostaining for orexin-A and Fos. After immobilized stress for 20 min and cold exposure at 4 °C for 30 min, approximately 24% and 15% of orexin-A-containing neurons expressed Fos-LI, respectively. These results suggest that orexins in the central nervous system may be involved in the activation of central CRF neurons induced by stress.