Posterior Bed Nucleus Of The Stria Terminalis Research Articles

Decrease in ERɑ within the BNST of sexually naïve male rats following an encounter with a novel female

Testosterone and its metabolites facilitate male-typical social behaviors in sexually experienced animals. The metabolite estradiol acts on estrogen receptors (ERs) within the bed nucleus of the stria terminalis (BNST) to facilitate socio-sexual behaviors. While circulating testosterone does not increase in naïve males, aromatase-expressing neurons within the BNST of naïve males are necessary for sex recognition, suggesting that local estradiol production may be responsible. In the present study, we examined ERɑ-immunoreactive (ir) cell number within the brain of sexually naïve male rats 24 h after an encounter with a novel animal. As expected, males investigated females more than males. Additionally, males that encountered females had fewer ERɑ-ir cells within both anterior and posterior BNST compared to those who encountered a novel male or a non-social control. There were no changes within the AVPV, MPN, or MeA. The decrease in ERɑ-ir cell number within the posterior BNST only occurred in males that encountered estrus females whereas the decrease in the anterior BNST occurred only in males that encountered non-estrus females. Additionally, anogenital investigations were correlated with fewer ERɑ-ir cells in the posterior BNST, while cage sniffing correlated with the number ERɑ-ir cells in the anterior BNST. There were no differences in serum testosterone 45 min or 24 h after the encounter, suggesting changes in ERɑ were due to local changes in estradiol levels. Our results expand upon previous research regarding the role of estradiol within the subregions of the BNST in naïve male rat socio-sexual behavior.

CB1 and CB2 receptors in the bed nucleus of the stria terminalis differently modulate anxiety-like behaviors in rats

The endocannabinoid system is implicated in anxiety, but the brain sites involved are not completely understood. The bed nucleus of the stria terminalis (BNST) has been related to anxiety and responses to aversive threats. Besides, endocannabinoid neurotransmission acting via CB1 receptors was identified in the BNST. However, the presence of CB2 receptors and the role of BNST endocannabinoid system in anxiety-like behaviors have never been reported. Therefore, this study investigated the presence of CB1 and CB2 receptors in the BNST and their role in anxiety-like behaviors. For this, gene expression of the endocannabinoid receptors was evaluated in samples from anterior and posterior BNST. Besides, behaviors were evaluated in the elevated plus-maze (EPM) in unstressed rats (trait anxiety-like behavior) and after exposure to restraint stress (restraint-evoked anxiety-like behavior) in rats treated with either the CB1 receptor antagonist AM251 or the CB2 receptor antagonist JTE907 into the anterior BNST. The presence of CB1 and CB2 receptors gene expression was identified in anterior and posterior divisions of the BNST. Bilateral microinjection of AM251 into the anterior BNST dose-dependently increased EPM open arms exploration in unstressed animals and inhibited the anxiety-like behavior in the EPM evoked by restraint. Conversely, intra-BNST microinjection of JTE907 decreased EPM open arms exploration in a dose-dependent manner and inhibited restraint-evoked behavioral changes in the EPM. Taken together, these results indicate that CB1 and CB2 receptors present in the BNST are involved in control of anxiety-like behaviors, and control by the latter is affected by previous stress experience.

Copulation induces expression of the immediate early gene Arc in mating-relevant brain regions of the male rat

The medial amygdala (MeA), bed nucleus of the stria terminalis (BNST), and medial preoptic area (mPOA) are important for the regulation of male sexual behavior. Sexual experience facilitates sexual behaviors and influences activity in these regions. The goal of this study was to determine whether sexual experience or copulation induces plasticity in the MeA, BNST, or mPOA of male rats, as indicated by changes in levels of Arc, which is indicative of activity-dependent synaptic plasticity in the brain. To this end, sexually naïve or experienced males were placed in mating arenas either alone, with an inaccessible estrus female, or with an accessible estrus female. Arc protein levels were then quantified in these three regions using immunohistochemistry. As expected, sexual experience facilitated copulation, as evidenced by a reduction in latencies to mount, intromit, and ejaculate. Copulation also increased the number of Arc-positive cells in the MeA, anterior BNST, posterior BNST, and the posterior mPOA, but not in the central-rostral region of the mPOA. Surprisingly, prior sexual experience did not impact levels of Arc, suggesting that copulation-induced Arc occurs in both sexually naïve and experienced males.

CRF receptor type 2 neurons in the posterior bed nucleus of the stria terminalis critically contribute to stress recovery

The bed nucleus of the stria terminalis (BNST) is critical in mediating states of anxiety, and its dysfunction has been linked to stress-related mental disease. Although the anxiety-related role of distinct subregions of the anterior BNST was recently reported, little is known about the contribution of the posterior BNST (pBNST) to the behavioral and neuroendocrine responses to stress. Previously, we observed abnormal expression of corticotropin-releasing factor receptor type 2 (CRFR2) to be associated with post-traumatic stress disorder (PTSD)-like symptoms. Here, we found that CRFR2-expressing neurons within the pBNST send dense inhibitory projections to other stress-related brain regions (for example, the locus coeruleus, medial amygdala and paraventricular nucleus), implicating a prominent role of these neurons in orchestrating the neuroendocrine, autonomic and behavioral response to stressful situations. Local CRFR2 activation by urocortin 3 depolarized the cells, increased the neuronal input resistance and increased firing of action potentials, indicating an enhanced excitability. Furthermore, we showed that CRFR2-expressing neurons within the pBNST are critically involved in the modulation of the behavioral and neuroendocrine response to stress. Optogenetic activation of CRFR2 neurons in the pBNST decreased anxiety, attenuated the neuroendocrine stress response, ameliorated stress-induced anxiety and impaired the fear memory for the stressful event. Moreover, activation following trauma exposure reduced the susceptibility for PTSD-like symptoms. Optogenetic inhibition of pBNST CRFR2 neurons yielded opposite effects. These data indicate the relevance of pBNST activity for adaptive stress recovery.

Brain CRF-binding protein modulates aspects of maternal behavior under stressful conditions and supports a hypo-anxious state in lactating rats

Reduced corticotropin-releasing factor (CRF) receptor activation in the postpartum period is essential for adequate maternal behavior. One of the factors contributing to this hypo-activity might be the CRF-binding protein (CRF-BP), which likely reduces the availability of free extracellular CRF/urocortin 1. Here, we investigated behavioral effects of acute CRF-BP inhibition using 5μg of CRF(6-33) administered either centrally or locally within different parts of the bed nucleus of the stria terminalis (BNST) in lactating rats. Additionally, we assessed CRF-BP expression in the BNST comparing virgin and lactating rats.Central CRF-BP inhibition increased maternal aggression during maternal defense but did not affect maternal care or anxiety-related behavior. CRF-BP inhibition in the medial-posterior BNST had no effect on maternal care under non-stress conditions but impaired the reinstatement of maternal care following stressor exposure. Furthermore, maternal aggression, particularly threat behavior, and anxiety-related behavior were elevated by CRF-BP inhibition in the medial-posterior BNST. In the anterior–dorsal BNST, CRF-BP inhibition increased only non-maternal behaviors following stress. Finally, CRF-BP expression was higher in the anterior compared to the posterior BNST but was not different between virgin and lactating rats in either region.Our study demonstrates a key role of the CRF-BP, particularly within the BNST, in modulating CRF's impact on maternal behavior. The CRF-BP is important for the reinstatement of maternal care after stress, for modulating threat behavior during an aggressive encounter and for maintaining a hypo-anxious state during lactation. Thus, the CRF-BP likely contributes to the postpartum-associated down-regulation of the CRF system in a brain region-dependent manner.

PACAP in the BNST Produces Anorexia and Weight Loss in Male and Female Rats

Recent gene association studies have implicated pituitary adenylate cyclase-activating peptide (PACAP) systems in several psychiatric disorders associated with stressor exposure, and we have argued that many of the behavioral consequences of repeated stressor exposure may depend on the expression of PACAP in the bed nucleus of the stria terminalis (BNST). One behavioral consequence of the activation of stress systems can be anorexia and subsequent weight loss, and both the activation of central PACAP systems as well as neuronal activity in the BNST have also been associated with anorexic states in rodents. Hence, we investigated the regulation of food and water intake and weight loss following BNST PACAP infusion. BNST PACAP38 dose-dependently decreased body weight, as well as food and water intake in the first 24 h following infusion. Because different BNST subregions differentially regulate stress responding, we further examined the effects of PACAP38 in either the anterior or posterior BNST. Anterior BNST PACAP38 infusion did not alter weight gain, whereas posterior PACAP38 infusion resulted in weight loss. PACAP38 infused into the lateral ventricles did not alter weight, suggesting that the effects of BNST-infused PACAP were not mediated by leakage into the ventricular system. These data suggest that PACAP receptor activation in posterior BNST subregions can produce anorexia and weight loss, and corroborate growing data implicating central PACAP activation in mediating the consequences of stressor exposure.

Basal regulation of HPA and dopamine systems is altered differentially in males and females by prenatal alcohol exposure and chronic variable stress.

Effects of prenatal alcohol exposure (PAE) on central nervous system function include an increased prevalence of mental health problems, including substance use disorders (SUD). The hypothalamic-pituitary-adrenal (HPA) and dopamine (DA) systems have overlapping neurocircuitries and are both implicated in SUD. PAE alters both HPA and dopaminergic activity and regulation, resulting in increased HPA tone and an overall reduction in tonic DA activity. However, effects of PAE on the interaction between HPA and DA systems have not been investigated. The present study examined PAE effects on basal regulation of central stress and DA systems in key brain regions where these systems intersect. Adult Sprague-Dawley male and female offspring from prenatal alcohol-exposed (PAE), pairfed (PF), and ad libitum-fed control (C) groups were subjected to chronic variable stress (CVS) or remained as a no stress (non-CVS) control group. Corticotropin releasing hormone (CRH) mRNA, as well as glucocorticoid and DA receptor (DA-R) expression were measured under basal conditions 24h following the end of CVS. We show, for the first time, that regulation of basal HPA and DA systems, and likely, HPA-DA interactions, are altered differentially in males and females by PAE and CVS. PAE augmented the typical attenuation in weight gain during CVS in males and caused increased weight loss in females. Increased basal corticosterone levels in control, but not PAE, females suggest that PAE alters the profile of basal hormone secretion throughout CVS. CVS downregulated basal CRH mRNA in the prefrontal cortex and throughout the bed nucleus of the stria terminalis (BNST) in PAE females but only in the posterior BNST of control females. PAE males and females exposed to CVS exhibited more widespread upregulation of basal mineralocorticoid receptor mRNA throughout the hippocampus, and an attenuated decrease in DA-R expression throughout the nucleus accumbens and striatum compared to CVS-exposed control males and females. Overall, these findings enhance our understanding of PAE effects on the cross-talk between HPA and DA systems, and provide insight into possible mechanisms underlying mental health problems that are related to stress and DA signaling, including SUD, which have a high prevalence among individuals with FASD.

Photoperiod affects estrogen receptor α, estrogen receptor β and aggressive behavior

AbstractEstrogens have important effects on male and female social behavior. Despite growing knowledge of the anatomy and behavioral effects of the two predominant estrogen receptor subtypes in mammals (ERα and ERβ), relatively little is known about how these receptors respond to salient environmental stimuli. Many seasonally breeding species respond to changing photoperiods that predict seasonal changes in resource availability. We characterized the effects of photoperiod on aggressive behavior in two species of Peromyscus that exhibit gonadal regression in short days. P. polionotus (old field mice) were more aggressive than P. maniculatus (deer mice) and both species were more aggressive in short days. We used immunocytochemistry and real‐time polymerase chain reaction to characterize the effects of photoperiod on ERα and ERβ expression. In both species ERα‐immunoreactive staining in the posterior bed nucleus of the stria terminalis (BNST) was increased in short vs. long days. Both species had reduced ERβ‐immunoreactive expression in the posterior BNST in short days. In the medial amygdala ERβ immunoreactivity was increased in long days for both species. Using real‐time polymerase chain reaction on punch samples that included the BNST, we observed that ERα mRNA was increased and ERβ mRNA was decreased in short days. These data suggest that the effects of photoperiod on ERα and ERβ expression may thus have important behavioral consequences.

Physiological Mapping of Local Inhibitory Inputs to the Hypothalamic Paraventricular Nucleus

Local inhibitory synaptic inputs to neurons of the rat hypothalamic paraventricular nucleus (PVN) were studied by using glutamate microstimulation and conventional intracellular and whole-cell patch-clamp recording in coronal, horizontal, and parasagittal slices of rat hypothalamus. PVN cells were classified as magnocellular or parvocellular neurons on the basis of electrophysiological and post hoc immunohistochemical analyses; GABA-producing neurons were localized with in situ hybridization. Glutamate microstimulation of different sites around the PVN evoked volleys of postsynaptic potentials in 43% of the PVN neurons tested. Some responses to stimulation at each site were blocked by bicuculline, suggesting that they were mediated by the activation of presynaptic GABA neurons. In the coronal plane, presynaptic inhibitory sites were located lateral to the PVN and ventral to the fornix, corresponding to the lateral hypothalamic area and the posterior bed nucleus of the stria terminalis (BNST). In the horizontal plane, presynaptic inhibitory sites were found rostral, lateral, and caudal to the nucleus, corresponding to parts of the anterior hypothalamic area, the posterior BNST, the medial preoptic area, and the dorsomedial hypothalamus. In the parasagittal plane, presynaptic inhibitory neurons were revealed at sites rostral and caudal to the nucleus, corresponding to the medial preoptic area and the dorsomedial hypothalamus, and in a site dorsal to the optic chiasm that included the suprachiasmatic nucleus. These presynaptic sites each contained GABA-producing neurons based on in situ hybridization with a glutamic acid decarboxylase riboprobe and together formed a three-dimensional ring around the PVN. Unexpectedly, both magnocellular and parvocellular neurons received inhibitory synaptic inputs from common sites.

Neuropeptide Y in Hamster Limbic Nuclei: Lack of Colocalization With Substance P

The medial nucleus of the amygdala (Me), bed nucleus of the stria terminalis (BNST), and medial preoptic area (MPOA) regulate copulation in the male hamster. The present study identified neuropeptide Y-immunoreactive (NPY-IR) neurons in the BNST and Me with the greatest concentration in the posteromedial and posteriordorsal subdivisions of these nuclei, respectively. NPY-IR fibers are found in all three nuclei with dense plexi of NPY-IR varicosities in the most medial subdivisions. Substance P neurons are also densely concentrated in the posterior BNST and Me; however, no neurons contained both peptides. Thus, NPY and substance P neurons comprise two distinct populations within the BNST and Me of the hamster.

Neuropeptide Y in hamster limbic nuclei: lack of colocalization with substance P.

The medial nucleus of the amygdala (Me), bed nucleus of the stria terminalis (BNST), and medial preoptic area (MPOA) regulate copulation in the male hamster. The present study identified neuropeptide Y-immunoreactive (NPY-IR) neurons in the BNST and Me with the greatest concentration in the posteromedial and posteriordorsal subdivisions of these nuclei, respectively. NPY-IR filters are found in all three nuclei with dense plexi of NPY-IR varicosities in the most medial subdivisions. Substance P neurons are also densely concentrated in the posterior BNST and Me; however, no neurons contained both peptides. Thus, NPY and substance P neurons comprise two distinct populations within the BNST and Me of the hamster.

Sexually dimorphic expression of androgen receptor immunoreactivity by somatostatin neurones in rat hypothalamic periventricular nucleus and bed nucleus of the stria terminalis.

Gonadal steroids exert important regulatory actions on the hypothalamic neurones regulating growth hormone secretion and are believed to play a role in generating its sexually dimorphic pattern of secretion. Recent evidence indicates that estrogen actions on one of these neural populations, the periventricular somatostatin (SOM) neurones, are likely to be indirect as they do not possess nuclear estrogen receptors in either sex although androgen receptors (ARs) have been reported within these cells in male rats. The present study has used double-labelling immunocytochemistry procedures to examine whether sex differences exist in AR expression by SOM neurones located in the periventricular nucleus and bed nucleus of the stria terminalis (BNST). Within the hypothalamus, SOM-immunoreactive neurones were found concentrated in the periventricular nucleus while both anterior and posterior divisions of the BNST contained scattered populations of SOM cells. Cells immunoreactive for the AR were detected in all of these areas. Although the intensity of AR cell nuclei staining was equivalent in males and females in regions such as the lateral septum, the intensity of AR staining in many individual cells of the periventricular nucleus and posterior BNST of the female was reduced when compared with the male. Double-labelling experiments revealed that approximately 40% of periventricular SOM neurones expressed AR immunoreactivity in the male compared with significantly (P < 0.01) fewer cells in the female (approximately 7%). In the BNST, double-labelled cells were only detected within the principle encapsulated, interfascicular and transverse nuclei of its posterior division. Approximately 60% of SOM cells in these nuclei expressed AR immunoreactivity in the male while significantly (P < 0.01) fewer did so in the female (approximately 25%). These results indicate that substantial sex differences exist in AR expression by SOM neurones in both the periventricular nucleus and BNST. Such differences in AR expression by periventricular SOM cells may contribute to their sexuality dimorphic nature and, consequently, sex differences in growth hormone secretion.

Sex difference in coexpression by galanin neurons accounts for sexual dimorphism of vasopressin in the bed nucleus of the stria terminalis.

Vasopressin (VP) neurons in the bed nucleus of the stria terminalis (BNST) are steroid sensitive and sexually dimorphic. The number of VP messenger RNA (mRNA)-expressing neurons is larger in male than in female rats. This initial observation suggested that sexual dimorphism resulted from enhanced proliferation and/or survival of VP neurons after gonadal hormone exposure during the critical perinatal period. However, galanin (GAL) and VP mRNAs were recently reported to be coexpressed in the BNST of adult male rats, and GAL gene expression, unlike VP gene expression, is not sexually dimorphic. These findings are consistent with the hypothesis that the sex difference in VP cell number in the BNST results from a sex difference in the number of GAL neurons dedicated to express the VP gene. To test this hypothesis, double in situ hybridization histochemistry was performed for GAL and VP mRNAs in the BNST of adult male and female rats. For quantification, the posterior BNST was divided into its two anatomical regions: medial (BSTM) and lateral (BSTL) divisions. Extending previous results for the whole BNST, the number of GAL-expressing cells in either the BSTM or the BSTL was not sexually dimorphic. A significant sex difference was found in the number of GAL cells coexpressing VP in the BSTM (mean +/- SE, male, 124 +/- 8; female, 56 +/- 6; P < or = 0.0001), but not in the BSTL (male, 80 +/- 9; female, 83 +/- 15). Accordingly, the number of cells expressing GAL mRNA only was significantly lower (P < or = 0.002) in the BSTM of male (43 +/- 5) than in female (85 +/- 9) rats. Evidence is provided that the reduced incidence of coexpression of VP by GAL neurons in the BSTM of female rats may account for the reported sex difference in VP cell number in the entire BNST. The results suggest that gonadal hormones in the perinatal period may not influence the proliferation and/or survival of VP neurons in the BNST per se but influence, instead, the capacity of GAL neurons to synthesize VP.

Involvement of the bed nucleus of the stria terminalis in tonic regulation of paraventricular hypothalamic CRH and AVP mRNA expression.

The bed nucleus of the stria terminalis (BNST) occupies a central position in pathways regulating hypothalamo-pituitary-adrenocortical (HPA) stress regulation. The potential role of the BNST in tonic neural control of HPA function was assessed by examining effects of selective BNST lesions on expression of ACTH secretagogues in HPA-integrative neurons of the medial parvocellular paraventricular nucleus. Anterior BNST lesions (ABN) involved major portions of the anteromedial, anterolateral, ventromedial, ventrolateral, dorsolateral and juxtacapsular subnuclei. These lesions resulted in significant (30%) decreases in corticotropin-releasing hormone (CRH) mRNA expression across the rostrocaudal extent of the medial parvocellular PVN, with no accompanying changes in basal arginine vasopressin (AVP) mRNA levels. Posterior BNST (PBN) lesions involved large but subtotal damage to the posterior intermediate, posterior medial, posterior lateral and preoptic subnuclei; these lesions resulted in small but significant changes in CRH mRNA and slight increases in number of AVP mRNA-producing parvocellular neurons. PBN effects on CRH mRNA expression were most pronounced at the caudal extent of the medial parvocellular zone, suggesting a topographic input from the posterior BNST to the PVN that is only partially compromised by PBN lesions. Analysis of individual cases revealed a correlation between damage of the anterolateral BNST and decreased CRH mRNA levels, and damage of the posterior intermediate and/or posterior medial BNST and increased CRH mRNA levels. The results suggest differential BNST input into HPA regulation, perhaps reflecting the diversity of limbic input into the BNST region.

Absence of estrogen receptor immunoreactivity in somatostatin (SRIF) neurons of the periventricular nucleus but sexually dimorphic colocalization of estrogen receptor and SRIF immunoreactivities in neurons of the bed nucleus of the stria terminalis.

The mechanisms by which somatostatin (SRIF) neurons in the periventricular nucleus and bed nucleus of the stria terminalis (BNST) are differentially regulated by gonadal steroids are unknown. Studies have shown an overlap in the distribution of estrogen receptor and SRIF immunoreactivities in these areas, giving rise to the possibility that SRIF neurons are regulated directly by gonadal steroids. In this study we have used double labeling immunocytochemistry to address the question of whether SRIF neurons in the periventricular region and BNST possess estrogen receptors in male and female rats. Short-term (2- to 4-day) gonadectomized rats with or without colchicine pretreatment for 16-18 h were processed for immunocytochemical staining using monoclonal estrogen receptor (H222) and polyclonal SRIF antisera. Single staining for SRIF and the estrogen receptor in rostral hypothalamic areas showed that the only sites of significant overlap between the two immunoreactivities were in the dorsal half of the periventricular region and posterior BNST. No sex differences were detected in the numbers of SRIF- or estrogen receptor-immunoreactive cells in the dorsal periventricular region. Sequential double-staining techniques demonstrated that periventricular SRIF neurons do not possess estrogen receptor immunoreactivity in either the male or female rat. However, double-labeled cells were readily detected in the posterior division of the BNST in male rats treated with colchicine. No colocalization was detected in the BNST of the female. These results show that the periventricular SRIF neurons controlling GH secretion do not possess estrogen receptor immunoreactivity in either sex and suggest that effects of testosterone and estradiol on SRIF messenger RNA expression in these cells through the estrogen receptor are indirect. In contrast, we provide evidence of a substantial sex difference in the localization of estrogen receptors within SRIF neurons of the BNST.

Absence of estrogen receptor immunoreactivity in somatostatin (SRIF) neurons of the periventricular nucleus but sexually dimorphic colocalization of estrogen receptor and SRIF immunoreactivities in neurons of the bed nucleus of the stria terminalis

The mechanisms by which somatostatin (SRIF) neurons in the periventricular nucleus and bed nucleus of the stria terminalis (BNST) are differentially regulated by gonadal steroids are unknown. Studies have shown an overlap in the distribution of estrogen receptor and SRIF immunoreactivities in these areas, giving rise to the possibility that SRIF neurons are regulated directly by gonadal steroids. In this study we have used double labeling immunocytochemistry to address the question of whether SRIF neurons in the periventricular region and BNST possess estrogen receptors in male and female rats. Short-term (2- to 4-day) gonadectomized rats with or without colchicine pretreatment for 16-18 h were processed for immunocytochemical staining using monoclonal estrogen receptor (H222) and polyclonal SRIF antisera. Single staining for SRIF and the estrogen receptor in rostral hypothalamic areas showed that the only sites of significant overlap between the two immunoreactivities were in the dorsal half of the periventricular region and posterior BNST. No sex differences were detected in the numbers of SRIF- or estrogen receptor-immunoreactive cells in the dorsal periventricular region. Sequential double-staining techniques demonstrated that periventricular SRIF neurons do not possess estrogen receptor immunoreactivity in either the male or female rat. However, double-labeled cells were readily detected in the posterior division of the BNST in male rats treated with colchicine. No colocalization was detected in the BNST of the female. These results show that the periventricular SRIF neurons controlling GH secretion do not possess estrogen receptor immunoreactivity in either sex and suggest that effects of testosterone and estradiol on SRIF messenger RNA expression in these cells through the estrogen receptor are indirect. In contrast, we provide evidence of a substantial sex difference in the localization of estrogen receptors within SRIF neurons of the BNST.