ApoE isoform‐dependent deficits in extinction of contextual fear conditioning

The three major human apoE isoforms (apoE2, apoE3 and apoE4) are encoded by distinct alleles (?2, ?3 and ?4). Compared with ?3, ?4 is associated with increased risk to develop Alzheimer's disease (AD), cognitive impairments in Parkinson's disease (PD), and other conditions. In contrast, a recent study indicated an increased susceptibility to the recurring and re‐experiencing symptom cluster of Post‐Traumatic Stress Disorder (PTSD), as well as related memory impairments, in patients carrying at least one ?2 allele. Contextual fear conditioning and extinction are used in human and animal models to study this symptom cluster. In this study, acquisition (day 1, training), consolidation (day 2, first day of re‐exposure) and extinction (days 2–5) of conditioned contextual fear in human apoE2, apoE3 and apoE4 targeted replacement and C57BL/6J wild‐type (WT) mice was investigated. Male and female apoE2 showed acquisition and retrieval of conditioned fear, but failed to exhibit extinction. In contrast, WT, apoE3 and apoE4 mice showed extinction. While apoE2 mice exhibited lower freezing in response to the context on day 2 than apoE3 and apoE4 mice, this cannot explain their extinction deficit as WT mice exhibited similar freezing levels as apoE2 mice on day 2 but still exhibited extinction. Elevating freezing through extended training preserved extinction in controls, but failed to ameliorate extinction deficits in apoE2 animals. These data along with clinical data showing an association of apoE2 with susceptibility to specific symptom clusters in PTSD supports an important role for apoE isoform in the extinction of conditioned fear.     

Enhanced corticosterone concentrations and attenuated Fos expression in the medial amygdala of female oxytocin knockout mice exposed to psychogenic stress

Centrally released oxytocin (OT) is believed to attenuate the response of the hypothalamic-pituitary-adrenal (HPA) axis to psychogenic stress. To test this hypothesis, we measured plasma corticosterone concentrations and Fos-immunoreactive protein in the paraventricular nucleus of the hypothalamus (PVN) and limbic brain areas of female wild-type and OT knockout mice that were exposed to a shaker platform, a predominantly psychogenic stress. Plasma corticosterone concentrations after shaker stress were higher in female OT knockout mice than wild-type mice. Genotypic differences in the corticosterone response after shaker stress persisted across all stages of the estrous cycle and when mice were conditioned to repeated shaker stress. Shaker stress activated Fos in OT-positive neurons of wild-type mice and corticotropin-releasing hormone-positive, but not vasopressin-positive, neurons within the PVN of wild-type and OT knockout mice. Fos expression was also increased after shaker stress in the bed nucleus of the stria terminalis, medial and central nuclei of the amygdala, medial preoptic area, and the paraventricular nucleus of the thalamus of wild-type and OT knockout mice. However, Fos expression in the medial amygdala was significantly lower in female OT knockout mice than wild-type mice. Our findings indicate heightened stress-induced corticosterone release in female OT knockout mice. Therefore, the results suggest that OT pathways play a role in attenuating the HPA axis response to psychogenic stress in female mice.     

Peptide immunoreactive neurons in the amygdala and the bed nucleus of the stria terminalis project to the midbrain central gray in the rat.

The central nucleus of the amygdala, bed nucleus of the stria terminalis, and central gray are important components of the neural circuitry responsible for autonomic and behavioral responses to threatening or stressful stimuli. Neurons of the amygdala and bed nucleus of the stria terminalis that project to the midbrain central gray were tested for the presence of peptide immunoreactivity. To accomplish this aim, a combined immunohistochemical and retrograde tracing technique was used. Maximal retrograde labeling was observed in the amygdala and bed nucleus of the stria terminalis after injections of retrograde tracer into the caudal ventrolateral midbrain central gray. The majority of the retrogradely labeled neurons in the amygdala were located in the medial central nucleus, although many neurons were also observed in the lateral subdivision of the central nucleus. Most of the retrogradely labeled neurons in the BST were located in the ventral and posterior lateral subdivisions, although cells were also observed in most other subdivisions. Retrogradely labeled neurotensin, corticotropin releasing factor (CRF), and somatostatin neurons were mainly observed in the lateral central nucleus and the dorsal lateral BST. Retrogradely labeled substance P-immunoreactive cells were found in the medial central nucleus and the posterior and ventral lateral BST. Enkephalin-immunoreactive retrogradely labeled cells were not observed in the amygdala or bed nucleus of the stria terminalis. A few cells in the hypothalamus (paraventricular and lateral hypothalamic nuclei) that project to the central gray also contained CRF and neurotensin immunoreactivity. The results suggest the amygdala and the bed nucleus of the stria terminalis are a major forebrain source of CRF, neurotensin, somatostatin, and substance P terminals in the midbrain central gray.     

Increased fear- and stress-related anxiety-like behavior in mice lacking tuberoinfundibular peptide of 39 residues

Tuberoinfundibular peptide of 39 residues (TIP39) is synthesized by two groups of neurons, one in the subparafascicular area at the caudal end of the thalamus and the other in the medial paralemniscal nucleus within the lateral brainstem. The subparafascicular TIP39 neurons project to a number of brain regions involved in emotional responses, and these regions contain a matching distribution of a receptor for TIP39, the parathyroid hormone 2 receptor (PTH2-R). We have now evaluated the involvement of TIP39 in anxiety-related behaviors using mice with targeted null mutation of the TIP39 gene (Tifp39). Tifp39(-/-) mice (TIP39-KO) did not significantly differ from wild-type (WT) littermates in the open field, light/dark exploration and elevated plus-maze assays under standard test conditions. However, the TIP39-KO engaged in more active defensive burying in the shock-probe test. In addition, when tested under high illumination or after restraint, TIP39-KO displayed significantly greater anxiety-like behavior in the elevated plus-maze than WT. In a Pavlovian fear-conditioning paradigm, TIP39-KO froze more than WT during training and during tone and context recall but showed normal fear extinction. Disruption of TIP39 projections to the medial prefrontal cortex, lateral septum, bed nucleus of the stria terminalis, hypothalamus and amygdala likely account for the fear- and anxiety-related phenotype of TIP39-KO. Current data support the hypothesis that TIP39 modulates anxiety-related behaviors following environmental provocation.     

Sex-related effects of sleep deprivation on depressive- and anxiety-like behaviors in mice

Anxiety and depressive symptoms are generated after paradoxical sleep deprivation (PSD). However, it is not clear whether PSD produces differential effects between females and males. The aim of this study was to assess the effect of PSD on anxiety- and depressive-like behaviors between sexes. Male and female BALB/c mice were divided in three groups: the control group, the 48-h PSD group and the 96-h PSD group. Immediately after PSD protocols, the forced swimming and open field test were applied. Sucrose consumption test was used to evaluate the middle-term effect of PSD. We found that corticosterone serum levels showed significant differences in the 96-h PSD females as compared to 96-h PSD males. In the open-field test, the 48-h and 96-h PSD females spent more time at the periphery of the field, and showed high locomotion as compared to males. In the elevated plus maze, the 48-h PSD females spent more time in closed arms than males, which is compatible with anxiety-like behavior. The forced swim test indicated that the 96-h PSD males spent more time swimming as compared to the 96-h PSD females. Remarkably, the 96-h PSD males had lower sucrose intake than the 96-h PSD females, which suggest that male mice have proclivity to develop a persistent depressive-like behavior late after PSD. In conclusion, male mice showed a significant trend to depressive-like behaviors late after sleep deprivation. Conversely, female have a strong tendency to display anxiety- and depressive-like behaviors immediately after sleep deprivation.     

Allopregnanolone induces state-dependent fear via the bed nucleus of the stria terminalis

Gonadal steroids and their metabolites have been shown to be important modulators of emotional behavior. Allopregnanolone (ALLO), for example, is a metabolite of progesterone that has been linked to anxiety-related disorders such as posttraumatic stress disorder. In rodents, it has been shown to reduce anxiety in a number of behavioral paradigms including Pavlovian fear conditioning. We have recently found that expression of conditioned contextual (but not auditory) freezing in rats can be suppressed by infusion of ALLO into the bed nucleus of the stria terminalis (BNST). To further explore the nature of this effect, we infused ALLO into the BNST of male rats prior to both conditioning and testing. We found that suppression of contextual fear occurred when the hormone was present during either conditioning or testing but not during both procedures, suggesting that ALLO acts in a state-dependent manner within the BNST. A shift in interoceptive context during testing for animals conditioned under ALLO provided further support for this mechanism of hormonal action on contextual fear. Interestingly, infusions of ALLO into the basolateral amygdala produced a state-independent suppression of both conditioned contextual and auditory freezing. Altogether, these results suggest that ALLO can influence the acquisition and expression of fear memories by both state-dependent and state-independent mechanisms.     

Production of monoclonal antibody to deltorphin-I and its immunocytochemical application to adult rat brain and cultured rat brain neurons

A monoclonal anti-deltorphin-I antibody specifically recognizing its NH2-terminal region was produced. In the adult rat brain sections, it recognized immunoreactive nerve fibers mainly in the bed nucleus of stria terminalis, central nucleus of amygdala, lateral hypothalamus, hippocampus, substantia nigra, periaqueductal gray and locus ceruleus. Occasionally, positive somata were localized in the bed nucleus of stria terminalis, central nucleus of amygdala, supraoptic and periventricular nuclei. In primarily cultured neurons from various brain regions of new-born rats, the antibody immunostained strongly neuronal somata and processes. The abundant DADTI-immunoreactive substance in the cultured neurons promises to provide an alternative pathway to search for the counterpart of deltorphins in mammals.     

REGIONAL DISTRIBUTION OF GLUTAMATE DECARBOXYLASE AND GABA WITHIN THE AMYGDALOID COMPLEX AND STRIA TERMINALIS SYSTEM OF THE RAT

The distribution of glutamate decarboxylase (GAD) and δ-amino butyric acid have been studied in the amygdaloid complex and in the stria terminalis system of the rat. The central and medial nuclei of the amygdala had significantly higher activities of GAD than the lateral olfactory tract nucleus, anterior amygdala, anterior lateral nucleus, posterior lateral nucleus, cortical nucleus, basomedial nucleus, basolateral nucleus, and pyriform cortex. The enzyme activity was about two and a half times higher in the central and medial nuclei than in the pyriform cortex. GABA was also significantly more concentratcd in these nuclei than in the pyriform cortex although this was not true for four other amino acids studied–glutamic acid, aspartic acid, taurine and glycine. GAD activity was also measured in the stria terminalis (the major afferent and efferent pathway of the amygdala) and in its bed nucleus. The enzyme activity was higher in the stria terminalis than in four other fibre tracts studied–the optic tract, anterior commissure, corpus callosum, and fimbria. GAD activity was exceptionally high in the bed nucleus of the stria terminalis particularly in its ventral part. The significance of the results are discussed in terms of what is known about the evolution and anatomy of the amygdala.     

Localization and mechanism of stimulatory feedback action of estrogen: effect of limbic forebrain implantation of estradiol benzoate on advancement of ovulation.

The sites and mechanism of the ovulation-inducing action of estradiol benzoate (EB) were studied by brain implantation of the crystalline steroid through chronically implanted outer cannula at 12:00 on diestrus day 2 in the 5-day cyclic rat. EB implantation in the medial amygdala or the bed nucleus of stria terminalis advanced cyclic changes in vaginal smears, timing of ovulatory LH release, and ovulation by 1 day, resulting in 4-day cycle. When implants in the bed nucleus of stria terminalis were placed for a shorter period of time on diestrus day 2, from 12:00 to 20:00, advancement of these parameters were similarly observed. Serum concentration of FSH and that of prolactin were significantly elevated at 20:00 on the same day in the rats implanted with EB in the medial amygdala or the bed nucleus of stria terminalis, compared with those in the non-treated controls. LH was not affected. The implantation in the arcuate nucleus was also effective to advance ovulation, but the anterior deafferentation prevented the effect. In contrast, EB implantation in the medial septal nucleus, the medial preoptic area, or the medial basal prechiasmatic area was consistently ineffective to advance vaginal cycle and ovulation. Multiunit activity in the arcuate nucleus showed an afternoon elevation on the day of implantation in these areas and as well on the day following, while it did not show such elevation on the day of implantation in the medial preoptic area. It is concluded that EB acts on the medial amygdala and the bed nucleus of stria terminalis in the mid-diestrus in 5-day cycle to stimulate FSH and prolactin release without affecting LH, which changes trigger a chain of reproductive events inducing early release of ovarian steroid responsible for early ovulatory gonadotropin release. The arcuate nucleus in one of the sites of stimulatory action of estrogen, but it requires the neural influence presumably from the medial amygdala and the bed nucleus of stria terminalis via the preoptic area for stimulating the ovulatory hormone release. EB exposure is considered to be endowed with the increase of its responsibility to this neural influence.     

Female mice deficient in alpha-fetoprotein show female-typical neural responses to conspecific-derived pheromones

The neural mechanisms controlling sexual behavior are sexually differentiated by the perinatal actions of sex steroid hormones. We recently observed using female mice deficient in alpha-fetoprotein (AFP-KO) and which lack the protective actions of AFP against maternal estradiol, that exposure to prenatal estradiol completely defeminized the potential to show lordosis behavior in adulthood. Furthermore, AFP-KO females failed to show any male-directed mate preferences following treatment with estradiol and progesterone, indicating a reduced sexual motivation to seek out the male. In the present study, we asked whether neural responses to male- and female-derived odors are also affected in AFP-KO female mice. Therefore, we compared patterns of Fos, the protein product of the immediate early gene, c-fos, commonly used as a marker of neuronal activation, between wild-type (WT) and AFP-KO female mice following exposure to male or estrous female urine. We also tested WT males to confirm the previously observed sex differences in neural responses to male urinary odors. Interestingly, AFP-KO females showed normal, female-like Fos responses, i.e. exposure to urinary odors from male but not estrous female mice induced equivalent levels of Fos protein in the accessory olfactory pathways (e.g. the medial part of the preoptic nucleus, the bed nucleus of the stria terminalis, the amygdala, and the lateral part of the ventromedial hypothalamic nucleus) as well as in the main olfactory pathways (e.g. the piriform cortex and the anterior cortical amygdaloid nucleus), as WT females. By contrast, WT males did not show any significant induction of Fos protein in these brain areas upon exposure to either male or estrous female urinary odors. These results thus suggest that prenatal estradiol is not involved in the sexual differentiation of neural Fos responses to male-derived odors.     

Neuropeptide Y innervation of amygdaloid and hypothalamic neurons that project to the dorsal vagal complex in rat

The anatomic relationship between neuropeptide Y (NPY)-immunoreactive terminals and forebrain areas in the rat that contain neurons that project to the dorsal vagal complex (DVC) was examined. To accomplish this, the combined retrograde fluorescent tracer and immunofluorescent technique was used. Neurons projecting to the DVC within the parvocellular divisions of the paraventricular nucleus of the hypothalamus were the most heavily innervated of the regions studied. A relatively high density of NPY-immunoreactive terminals innervated regions of the arcuate, dorsomedial and lateral hypothalamic areas that contained DVC efferent cells. Neurons that projected to the DVC within the medial division of the central nucleus of the amygdala and the lateral part of the bed nucleus of the stria terminalis were also innervated by NPY immunoreactive terminals. The results suggest an important role for NPY terminals in the modulation of neurons within the amygdala and hypothalamus that directly influence visceral-autonomic functions of the dorsal vagal complex. The source and possible function of NPY within these regions is discussed.     

Obesity-inducing amygdala lesions: examination of anterograde degeneration and retrograde transport

Small lesions centered in the posterodorsal region of the medial amygdala resulted in excessive weight gains in female rats. Unilateral lesions were nearly as effective as bilateral lesions in the first 48 h after surgery (+21 to +32 g). Assessment of lesion damage was done by both qualitative evaluation and by a quantitative grid-point counting method. The critical sites for weight gain were the intra-amygdaloid bed nucleus of the stria terminalis and the posterodorsal medial amygdaloid nucleus. Incidental damage to the overlying globus pallidus was negatively related to weight gain. The cupric silver method for demonstrating axonal degeneration was applied to brains with obesity-inducing lesions. A dense pattern of degenerating terminals was found in the lateral septum, amygdala, ventral striatum, and ventromedial hypothalamus. Degeneration in the paraventricular nucleus of the hypothalamus was scarce or absent. Small retrograde tracer injections made in either the intra-amygdaloid bed nucleus of the stria terminalis or in the posterodorsal medial amygdaloid nucleus labeled cells in the amygdala, lateral septum, and hypothalamus, reciprocating the anterograde projections from the amygdala to these areas. The data suggest that subdivisions of the posterodorsal amygdala participate in the regulation of feeding in a manner that is similar to the better-known role of this part of the brain in mediating reproductive behavior. Although topographical differences may exist within the amygdaloid and hypothalamic subdivisions regulating these two sexually dimorphic behaviors, the relays engaged by feeding-related connections and those related to reproduction are remarkably parallel.     

Dopamine D3 Receptor Mediates Preadolescent Stress-Induced Adult Psychiatric Disorders

Several studies have shown that repeated stressful experiences during childhood increases the likelihood of developing depression- and anxiety-related disorders in adulthood; however, the underlying mechanisms are not well understood. We subjected drd3-EGFP and drd3-null mice to daily, two hour restraint stress episodes over a five day period during preadolescence (postnatal day 35 to 39), followed by social isolation. When these mice reached adulthood (post-natal day > 90), we assessed locomotor behavior in a novel environment, and assessed depression-related behavior in the Porsolt Forced Swim test. We also measured the expression and function of dopamine D3 receptor in limbic brain areas such as hippocampus, nucleus accumbens and amygdala in control and stressed drd3-EGFP mice in adulthood. Adult male mice subjected to restraint stress during preadolescence exhibited both anxiety- and depression-related behaviors; however, adult female mice subjected to preadolescent restraint stress exhibited only depression-related behaviors. The development of preadolescent stress-derived psychiatric disorders was blocked by D3 receptor selective antagonist, SB 277011-A, and absent in D3 receptor null mice. Adult male mice that experienced stress during preadolescence exhibited a loss of D3 receptor expression and function in the amygdala but not in hippocampus or nucleus accumbens. In contrast, adult female mice that experienced preadolescent stress exhibited increased D3 receptor expression in the nucleus accumbens but not in amygdala or hippocampus. Our results suggest that the dopamine D3 receptor is centrally involved in the etiology of adult anxiety- and depression-related behaviors that arise from repeated stressful experiences during childhood.     

Sodium Phenylbutyrate and Edaravone Abrogate Chronic Restraint Stress-Induced Behavioral Deficits: Implication of Oxido-Nitrosative,Endoplasmic Reticulum Stress Cascade,and Neuroinflammation

Chronic stress exposure can produce deleterious effects on the hippocampus (HC) which eventually leads to cognitive impairment and depression. Endoplasmic reticulum (ER) stress has been reported as one of the major culprits in the development of stress-induced cognitive impairment and depression. We investigated the neuroprotective efficacy of sodium phenylbutyrate (SPB), an ER stress inhibitor, and edaravone, a free radical scavenger, against chronic restraint stress (CRS)-induced cognitive deficits and anxiety- and depressive-like behavior in mice. Adult male Swiss albino mice were restrained for 6 h/day for 28 days and injected (i.p.) with SPB (40 and 120 mg/kg) or edaravone (3 and 10 mg/kg) for the last seven days. After stress cessation, the anxiety- and depressive-like behavior along with spatial learning and memory were examined. Furthermore, oxido-nitrosative stress, proinflammatory cytokines, and gene expression level of ER stress-related genes were assessed in HC and prefrontal cortex (PFC). CRS-exposed mice showed anxiety- and depressive-like behavior, which was significantly improved by SPB and edaravone treatment. In addition, SPB and edaravone treatment significantly alleviated CRS-induced spatial learning and memory impairment. Furthermore, CRS-evoked oxido-nitrosative stress, neuroinflammation, and depletion of Brain-derived neurotrophic factor were significantly ameliorated by SPB and edaravone treatment. We found significant up-regulation of ER stress-related genes in both HC and PFC regions, which were suppressed by SPB and edaravone treatment in CRS mice. Our study provides evidence that SPB and edaravone exerted neuroprotective effects on CRS-induced cognitive deficits and anxiety- and depressive-like behavior, which is possibly coupled with inhibition of oxido-nitrosative stress, neuroinflammation, and ER stress cascade.     

Heat-killed Lactobacillus helveticus strain MCC1848 confers resilience to anxiety or depression-like symptoms caused by subchronic social defeat stress in mice

The gut microbiota is involved in the pathogenesis of stress-related disorders. Probiotics can benefit the central nervous system via the microbiota–gut–brain axis, which raises the possibility that probiotics are effective in managing depression. In the present study, we examined the effects of heat-killed Lactobacillus helveticus strain MCC1848 in subchronic and mild social defeat stress (sCSDS) model mice (a widely used animal model of depression). MCC1848 supplementation significantly enhanced the interaction time in the social interaction test and sucrose preference ratio in the sucrose preference test, suggesting that MCC1848 improved anxiety- or depressive-like behaviors in sCSDS mice. The gene expression profile analysis of the nucleus accumbens, which plays an important role in stress resilience, indicated that MCC1848 ameliorated sCSDS-induced gene expression alterations in signal transduction or nervous system development. These findings suggest that MCC1848 supplementation is useful as a preventive strategy for chronic-stress-induced depression.     

Vasopressin and aggression in cross-fostered California mice (Peromyscus californicus) and white-footed mice (Peromyscus leucopus)

To examine how developmental experiences alter neural pathways associated with adult social behavior, we cross-fostered pups between the more aggressive and monogamous California mouse (Peromyscus californicus) and the less aggressive and polygamous white-footed mouse (P. leucopus). Cross-fostered males became more like their foster parents when tested as adults. Male white-footed mice became more aggressive only in an aggression test in a neutral arena, whereas the territorial California mice became less aggressive in resident-intruder aggression test, as measured by attack latency. Only the species that displayed a change in resident-intruder aggression showed a change in arginine vasopressin (AVP) levels: cross-fostered California mice had significantly lower levels of AVP-immunoreactive (AVP-ir) staining than controls in the bed nucleus of the stria terminalis (BNST) and the supraoptic nucleus (SON) and a nonsignificant trend toward lower levels in the medial amygdala (MA). Neither species showed changes in AVP-ir staining in a control area, the paraventricular nucleus (PVN). The changes in AVP-ir staining in the BNST and SON may not be caused by stress because cross-fostering was not associated with changes in adult plasma concentrations of two steroid hormones, corticosterone and testosterone, that have been associated with stress-related alterations in AVP pathways. These results suggest that manipulating the early parental environment can directly alter both a neurotransmitter system and species-typical patterns of social behavior, but that these effects may vary between species and under different social contexts.     

Roles of testosterone and amygdaloid LTP induction in determining sex differences in fear memory magnitude

Women are thought to form fear memory more robust than men do and testosterone is suspected to play a role in determining such a sex difference. Mouse cued fear freezing was used to study the sex-related susceptibility and the role of testosterone in fear memory in humans. A 75-dB tone was found to provoke weak freezing, while 0.15-mA and 0.20-mA footshock caused strong freezing responses. No sex differences were noticed in the tone- or footshock-induced (naïve fear) freezing. Following the conditionings, female mice exhibited greater tone (cued fear)-induced freezing than did male mice. Nonetheless, female mice demonstrated indistinctive cued fear freezing across the estrous phases and ovariectomy did not affect such freezing in female mice. Orchidectomy enhanced the cued fear freezing in male mice. Systemic testosterone administrations and an intra-lateral nucleus of amygdala (LA) testosterone infusion diminished the cued fear freezing in orchidectomized male mice, while pretreatment with flutamide (Flu) eradicated these effects. Long-term potentiation (LTP) magnitude in LA has been known to correlate with the strength of the cued fear conditioning. We found that LA LTP magnitude was indeed greater in female than male mice. Orchidectomy enhanced LTP magnitude in males' LA, while ovariectomy decreased LTP magnitude in females' LA. Testosterone decreased LTP magnitude in orchidectomized males' LA and estradiol enhanced LTP magnitude in ovariectomized females' LA. Finally, male mice had lower LA GluR1 expression than female mice and orchidectomy enhanced the GluR1 expression in male mice. These findings, taken together, suggest that testosterone plays a critical role in rendering the sex differences in the cued fear freezing and LA LTP. Testosterone is negatively associated with LA LTP and the cued fear memory in male mice. However, ovarian hormones and LA LTP are loosely associated with the cued fear memory in female mice.     

Opiocortin and catecholamine input to CRF-immunoreactive neurons in rat forebrain

Neural input to distinct and separate populations of CRF-immunoreactive (ir) neurons in rat forebrain was investigated. The relationship of opiocortin and/or catecholamine fibers to different groups of CRF-containing neurons was elucidated using single and dual labeling immunocytochemical procedures. Antibodies to CRF, ACTH(1–39) and the catecholamine synthesizing enzymes which are tyrosine hydroxylase (TH), dopamine β-hydroxylase (DBH) and phenylethanolamine-N-methyltransferase (PNMT) were utilized. CRF-ir neuronal populations are localized predominantly in the following regions of rat forebrain: bed nucleus of stria terminalis, medial preoptic area, suprachiasmatic and paraventricular (PVN) nuclei of hypothalamus and central nucleus of amygdala. The present study demonstrates that CRF-ir neuronal groups in rat forebrain are not homogenous in that each population received a characteristic neural input. CRF-ir neurons in the PVN received a dense input of ACTH-, TH-, DBH-, and PNMT-ir fibers. In contrast, CRF-ir neurons in the central nucleus of amygdala are colocalized predominantly with TH-ir fiber/terminals. In the ventral portion of the bed nucleus of stria terminalis, TH-, ACTH- and DBH-ir fibers are demonstrated in close anatomical proximity to CRF-containing perikarya; in the dorsal portion of this nucleus, TH-ir fiber/terminals are colocalized with CRF-ir neurons. In the suprachiasmatic nucleus, neither opiocortin- nor catecholamine-immunostained fibers are observed in association with CRF-ir neurons. Our data suggest that there is a transmitter specificity of neural input to each CRF-ir neuronal population in rat forebrain.     

Changes in CNS response to neurotensin accompany the postpartum period in mice

Neurotensin (NT) is a highly conserved neuropeptide in mammals. Recent studies suggest that altered NT neurotransmission in postpartum females could promote the emergence of some maternal behaviors, including offspring protection. Here we evaluated how virgin and postpartum brains from mice selected for high maternal defense differ in response to NT. Virgin and postpartum mice were injected with either vehicle or 0.1 μg NT icv and brains were evaluated for c-Fos immunoreactivity, an indirect marker of neuronal activity. Using ANOVA analysis, common significant responses to NT were found in both female groups in four brain regions, including supraoptic nucleus, ventromedial nucleus, bed nucleus of stria terminalis dorsal, and a subregion of lateral septum (LS). For postpartum mice, only one additional region showed a significant response to NT relative to vehicle, whereas for virgin mice seven unique brain regions showed a significant c-Fos response: nucleus accumbens shell, paraventricular nucleus, central amygdala, and substantia nigra. Using a principal components analysis of c-Fos, we identified regions within each group with highly correlated activity. As expected, virgin and postpartum mice (vehicle conditions) showed different activity hubs and in the postpartum group the hubs matched regions linked to maternal care. The response to injected NT was different in the maternal and virgin groups with maternal mice showing a stronger coordinated activity in periaqueductal gray whereas virgin mice showed a stronger septal and amygdala linking of activity. Together, these results indicate neuronal responses of virgin and postpartum mice to NT and highlight pathways by which NT can alter maternal responses.