A novel treatment to enhance survival for end stage triple negative breast cancer using repurposed veterinary anthelmintics combined with gut­supporting/immune enhancing molecules.

Patients with end­stage metastatic disease have limited treatment options and those diagnosed with triple negative breast cancer (Her2, Estrogen receptor, Progesterone receptor) have a poor prognosis. Using a triple negative mammary tumor model selected for brain metastasis (4T1Br4) in the mouse, treatment options that may increase survival when therapeutics are applied at post­metastasis were assessed. Anti­parasitic benzimidazoles (BZs) destabilize microtubules, inhibit metabolic pathways, reduce cell proliferation, and induce apoptosis in tumor cells. Co­administration of two BZs was selected, oxfendazole (OFZ) and parbendazole (PBZ), shown to overcome resistance development in anthelmintic effects by imposing metabolic delay to assess if multiple BZ approach is also suitable to enhance anticancer effects. It has been previously reported that treatment of mammary tumor­bearing mice at an early stage with chitin microparticles (CMPs) decreased tumor growth and metastases by enhancing both innate M1 macrophage and TH1 adaptive immune response. Oral administration of CMPs was previously revealed to affect the gut in intestinal inflammation. A combination BZ (OFZ/PBZ) and CMP treatment was tested to target tumor development and metastasis and effects were compared in response to monotherapies of the same compounds or to untreated mice. The results demonstrated increased survival, decreased tumor cell proliferation, decreased metastasis in lungs and brain, increased levels of fecal SCFAs butyric, acetic, propionic and valeric acids with increased butyric and propionic acid levels in brain biopsies in combination treated compared with untreated mice. At the primary tumor, SCFA receptor FFAR2 expression was increased in combination treatment compared with untreated mice, suggestive of a non­invasive cancer phenotype. The superior cytotoxic effects of OFZ/PBZ were confirmed as opposed to single treatment with OFZ or PBZ using 3D spheroids generated from a human breast cancer cell line, MDA­MB­468. These data are compelling for treatment option possibility even at late stages of metastasized breast cancer.

Progressive generalized tonic-clonic seizures in a transgenic mouse model of adult-onset epilepsy: Implications for morphological changes in cortico-limbic and brainstem structures.

Video/cortical electroencephalography (EEG) is monitored to assess progressive severity of generalized tonic clonic seizures (GTCSs) in a transgenic mouse model of adult-onset epilepsy with increased death risk. The mice overexpress the brain derived neurotrophic factor (BDNF) in the forebrain under the calcium/calmodulin dependent protein kinase 2a (termed TgBDNF) and develop GTCSs in response to tail suspension/cage agitation stimulation at 3-4 months of age. With successive GTCSs (a total of 16 across 10 weeks of assessment), seizures became more severe as evidenced by increased duration of postictal generalized EEG suppression (PGES) associated with loss of posture/consciousness. Mice also developed spike wave discharges with behavioral arrest during the seizure recovery that increased in duration as a function of number of GTCSs. Overall seizure duration (from preictal spike to offset of PGES) and ictal spectral power (full spectra) were also increased. Half of the TgBDNF mice expired following a long period of PGES at the last recorded GTCS. Seizure-evoked general arousal impairment was associated with a striking decrease in total number of gigantocellular neurons of the brainstem nucleus pontis oralis along with increase in volumes of the anterior cingulate cortex and dorsal dentate gyrus in severely convulsive TgBDNF mice compared to litter-matched WT controls and non-convulsive TgBDNF mice. The latter effect was accompanied with an increase in total number of hippocampal granule neurons. These results provide structure-function associations in an animal model of adult-onset GTCSs that progressively increase in severity with clinical relevance for sudden unexpected death following generalized seizures.

Inter-individual differences in immune profiles of outbred rats screened for an emotional reactivity phenotype.

Inter-individual differences in emotional reactivity predict susceptibility versus resilience to mood pathology. Using experimentally-naïve outbred rats that vary in locomotor reactivity to the mild stress of an inescapable novel environment [i.e., top and bottom 1/3rd of the population identified as high responders (HR) and low responders (LR) respectively], we determined baseline variations in immune functions. Innate and adaptive immune responses vary basally in LRHR rats, namely a shift towards TH1 in LRs and TH2 in HRs was observed. These inter-individual variations in immune profiles in LRHRs could have significant implications in mood alterations and immune reactivity to microbes and cancer.

Hippocampal Y2 receptor-mediated mossy fiber plasticity is implicated in nicotine abstinence-related social anxiety-like behavior in an outbred rat model of the novelty-seeking phenotype.

Experimentally naïve outbred rats display varying rates of locomotor reactivity in response to the mild stress of a novel environment. Namely, some display high rates (HR) whereas some display low rates (LR) of locomotor reactivity. Previous reports from our laboratory show that HRs, but not LRs, develop locomotor sensitization to a low dose nicotine challenge and exhibit increased social anxiety-like behavior following chronic intermittent nicotine training. Moreover, the hippocampus, specifically hippocampal Y2 receptor (Y2R)-mediated neuropeptide Y signaling is implicated in these nicotine-induced behavioral effects observed in HRs. The present study examines the structural substrates of the expression of locomotor sensitization to a low dose nicotine challenge and associated social anxiety-like behavior following chronic intermittent nicotine exposure during adolescence in the LRHR hippocampi. Our data showed that the expression of locomotor sensitization to the low dose nicotine challenge and the increase in social anxiety-like behavior were accompanied by an increase in mossy fiber terminal field size, as well as an increase in spinophilin mRNA levels in the hippocampus in nicotine pre-trained HRs compared to saline pre-trained controls. Furthermore, a novel, selective Y2R antagonist administered systemically during 1 wk of abstinence reversed the behavioral, molecular and neuromorphological effects observed in nicotine-exposed HRs. These results suggest that nicotine-induced neuroplasticity within the hippocampus may regulate abstinence-related negative affect in HRs, and implicate hippocampal Y2R in vulnerability to the behavioral and neuroplastic effects of nicotine in the novelty-seeking phenotype.

Nicotine-induced anxiety-like behavior in a rat model of the novelty-seeking phenotype is associated with long-lasting neuropeptidergic and neuroplastic adaptations in the amygdala: effects of the cannabinoid receptor 1 antagonist AM251.

A rat model of the novelty-seeking phenotype predicts vulnerability to the expression of behavioral sensitization to nicotine, where locomotor reactivity to novelty is used to screen experimentally-naïve rats for high (HR) versus low (LR) responders. The present study examines the long-term neuropeptidergic and neuroplastic adaptations associated with the expression of locomotor sensitization to a low dose nicotine challenge and social anxiety-like behavior following chronic intermittent nicotine exposure during adolescence in the LRHR phenotype. Our data show that the expression of behavioral sensitization to nicotine and abstinence-related anxiety are detected in nicotine pre-exposed HRs even across a long (3 wks) abstinence. Moreover, these behavioral effects of nicotine are accompanied by a persistent imbalance between neuropeptide Y and corticotrophin releasing factor systems, and a persistent increase in brain-derived neurotrophic factor (BDNF) and spinophilin mRNA levels in the amygdala. Furthermore, treatment with the cannabinoid receptor 1 antagonist, AM251 (5 mg/kg) during a short (1 wk) abstinence is ineffective in reversing nicotine-induced anxiety, fluctuations in BDNF and spinophilin mRNAs, and the neuropeptidergic dysregulations in the amygdala; although this treatment is effective in reversing the expression of locomotor sensitization to challenge nicotine even after a long abstinence. Interestingly, the identical AM251 treatment administered during the late phase of a long abstinence further augments anxiety and associated changes in BDNF and spinophilin mRNA in the basolateral nucleus of the amygdala in nicotine pre-exposed HRs. These findings implicate long-lasting neuropeptidergic and neuroplastic changes in the amygdala in vulnerability to the behavioral effects of nicotine in the novelty-seeking phenotype.

Long-term effects of juvenile nicotine exposure on abstinence-related social anxiety-like behavior and amygdalar cannabinoid receptor 1 (CB1R) mRNA expression in the novelty-seeking phenotype.

A rat model of novelty-seeking phenotype predicts vulnerability to nicotine relapse where locomotor reactivity to novelty is used to rank high (HR) versus low (LR) responders. Present study investigates implication of cannabinoid receptor 1 (CB1R) in the basolateral (BLA) and the central (CeA) nuclei of amygdala in behaviorally sensitizing effects of nicotine and accompanying social anxiety following juvenile nicotine training and a 1- or 3-wk injection-free period in the novelty-seeking phenotype. Sprague-Dawley rats were phenotype screened, and received four, saline (1 ml/kg; s.c) or nicotine (0.35 mg/kg; s.c) injections, followed by a 1- or 3-wk injection-free period. Subsequently, animals were challenged with a low dose of nicotine (0.1 mg/kg; s.c.), subjected to the social interaction test and sacrificed. In situ hybridization histochemistry was used to assess CB1R messenger RNA (mRNA) levels in the amygdala. Nicotine pre-trained HRs displayed expression of locomotor sensitization to nicotine challenge along with enhanced social anxiety compared to saline pre-trained controls following a 1- or 3-wk injection-free period. HR-specific behavioral effects were accompanied by decreased CB1R mRNA levels in the CeA and the BLA following a 1-wk injection-free period. Decreased CB1R mRNA levels in both compartments of the amygdala were also observed following nicotine challenge in saline pre-trained HRs after a 3-wk injection-free period compared to HRs after a 1-wk injection-free period. These findings show robust, long-lasting expression of behavioral sensitization to nicotine in HRs associated with changes in amygdalar CB1R mRNA as a potential substrate for abstinence-related anxiety.

Stressful environmental and social stimulation in adolescence causes antidepressant-like effects associated with epigenetic induction of the hippocampal BDNF and mossy fibre sprouting in the novelty-seeking phenotype.

An outbred rat model of novelty-seeking phenotype can differentiate between rats that show high rates (high responders; HRs) versus low rates (low responders; LRs) of locomotor reactivity to a novel environment. In the present study, LR and HR rats were exposed to a regimen of environmental and social stimuli (ESS) consisting of 14 random exposures of isolation, crowding or novel environment, once per day during the peripubertal-juvenile period (postnatal days 28-41) or handled as controls. Twenty-four hours after the last ESS exposure or control handling, all animals were tested on the forced swim and social interaction tests for depressive-like and social anxiety-like behaviors respectively. The ESS exposure during the peripubertal-juvenile period led to antidepressive-like effects on the forced swim test associated with increase in acetylation of histones 3 and 4 at the promoter regions P2 and P4 of the brain-derived neurotrophic factor (BDNF) gene in the dorsal hippocampus of HRs. Moreover, epigenetic activation of the hippocampal BDNF in the HRs following ESS exposure was accompanied by increase in the supra-pyramidal mossy fibre (SP-MF) and total mossy fibre terminal field volumes compared to handled controls. These findings suggest that the ESS exposure in the peripubertal-juvenile period may constitute an example of environmental induction of the hippocampal BDNF, and may mimic behavioral effects of exogenous antidepressants in the HR phenotype.

Effects of a selective Y2R antagonist, JNJ-31020028, on nicotine abstinence-related social anxiety-like behavior, neuropeptide Y and corticotropin releasing factor mRNA levels in the novelty-seeking phenotype.

An outbred rat model of novelty-seeking phenotype has predictive value for the expression of locomotor sensitization to nicotine. When experimentally naïve rats are exposed to a novel environment, some display high rates of locomotor reactivity (HRs, scores ranking at top 1/3rd of the population), whereas some display low rates (LRs, scores ranking at bottom 1/3rd of the population). Basally, HRs display lower anxiety-like behavior compared to LRs along with higher neuropeptide Y (NPY) mRNA in the amygdala and the hippocampus. Following an intermittent behavioral sensitization to nicotine regimen and 1 wk of abstinence, HRs show increased social anxiety-like behavior in the social interaction test and robust expression of locomotor sensitization to a low dose nicotine challenge. These effects are accompanied by a deficit in NPY mRNA levels in the medial nucleus of the amygdala and the CA3 field of the hippocampus, and increases in Y2R mRNA levels in the CA3 field and corticotropin releasing factor (CRF) mRNA levels in the central nucleus of the amygdala. Systemic and daily injections of a Y2R antagonist, JNJ-31020028, during abstinence fully reverse nicotine-induced social anxiety-like behavior, the expression of locomotor sensitization to nicotine challenge, the deficit in the NPY mRNA levels in the amygdala and the hippocampus, as well as result an increase in Y2R mRNA levels in the hippocampus and the CRF mRNA levels in the amygdala in HRs. These findings implicate central Y2R in neuropeptidergic regulation of social anxiety in a behavioral sensitization to nicotine regimen in the LRHR rats.

Vulnerability to nicotine abstinence-related social anxiety-like behavior: molecular correlates in neuropeptide Y, Y2 receptor and corticotropin releasing factor.

An outbred rat model of the novelty-seeking phenotype is used to study nicotine vulnerability, where experimentally naïve rats were phenotype screened as high or low responders (HRs or LRs, ranking in the upper or lower one-third of the population respectively) based on locomotor activity displayed in a novel environment. Following nicotine training and abstinence, HR animals pre-trained with nicotine showed expression of locomotor sensitization to nicotine challenge along with enhanced social anxiety-like behavior in the social interaction test compared to saline pre-trained controls. HR rats also showed a downregulation in neuropeptide Y (NPY) mRNA levels in the medial nucleus of amygdala and the CA1 field of the hippocampus, an upregulation in Y2 mRNA levels in the CA3 field of the hippocampus, and an upregulation in the corticotropin releasing factor (CRF) mRNA levels in the central nucleus of the amygdala. These findings implicate dysregulations in the NPY-CRF systems in the HR hippocampus and amygdala associated with the emergence of social anxiety-like behavior, and a novel Y2R-mediated pathway in nicotine relapse.

Effects of a cannabinoid receptor (CB) 1 antagonist AM251 on behavioral sensitization to nicotine in a rat model of novelty-seeking behavior: correlation with hippocampal 5HT.

RATIONALE: There are marked individual differences in the efficacy of mainstream nicotine cessation agents in preventing relapse. A rat model of novelty-seeking phenotype was reported to have predictive value for psychostimulant taking behavior where locomotor reactivity to novelty is used to rank high (HR, highest 1/3) versus low (LR, lowest 1/3) responsiveness to novelty in outbred rats. We tested the hypothesis that a cannabinoid receptor (CB) 1 antagonist that is in clinical trials for smoking cessation may reverse behaviorally sensitizing effects of nicotine in HRs and repeated nicotine-induced elevations in hippocampal 5HT. MATERIALS AND METHODS: Adolescent LRHR rats underwent intermittent behavioral sensitization to nicotine regimen with or without a CB1 receptor antagonist AM251 or bupropion treatment following nicotine training during 1 week of nicotine-free period. Expression of behavioral sensitization to nicotine was assessed in response to a low-dose nicotine challenge. Using the same sensitization regimen and therapeutic treatments, hippocampal 5HT levels were measured via in vivo microdialysis in response to the nicotine challenge. RESULTS: HR but not LR animals showed behavioral sensitization to a low-dose nicotine challenge following intermittent nicotine training and 1 week of injection-free period. AM251 (5 mg/kg, i.p.) but not bupropion administration during injection-free period successfully reversed locomotor sensitization to nicotine challenge in HRs. AM251 treatment also reversed nicotine-induced elevations in extracellular 5HT in the HR hippocampal hilus. CONCLUSION: These data suggest that CB1 antagonists may prevent locomotor sensitization to nicotine and reverse nicotine-induced elevations in hippocampal 5HT in high novelty seekers.

Response of olfactory axons to loss of synaptic targets in the adult mouse.

Glomerular convergence has been proposed to rely on interactions between like olfactory axons, however topographic targeting is influenced by guidance molecules encountered in the olfactory bulb. Disruption of these cues during development misdirects sensory axons, however little is known about the role of bulb-derived signals in later life, as new axons arise during turnover of the olfactory sensory neuron (OSN) population. To evaluate the contribution of bulb neurons in maintaining topographic projections in adults, we ablated them with N-methyl-d-aspartate (NMDA) in P2-IRES-tauLacZ mice and examined how sensory axons responded to loss of their postsynaptic partners. NMDA lesion eliminated bulb neurons without damage to sensory axons or olfactory ensheathing glia. P2 axons contained within glomeruli at the time of lesion maintained convergence at these locations; there was no evidence of compensatory growth into the remnant tissue. Delayed apoptosis of OSNs in the target-deprived epithelium led to declines in P2 neuron number as well as the gradual atrophy, and in some cases complete loss, of P2 glomeruli in lesioned bulbs by 3 weeks. Increased cell proliferation in the epithelium partially restored the OSN population, and by 8 weeks, new P2 axons distributed within diverse locations in the bulb remnant and within the anterior olfactory nucleus. Prior studies have suggested that initial development of olfactory topography does not rely on synapse formation with target neurons, however the present data demonstrate that continued maintenance of the sensory map requires the presence of sufficient numbers and/or types of available bulbar synaptic targets.

Hippocampus modulates the behaviorally-sensitizing effects of nicotine in a rat model of novelty-seeking: potential role for mossy fibers.

Present experiments investigate interactions between a rat model of the novelty-seeking phenotype and psychomotor sensitization to nicotine (NIC) in adolescence, and the potential role of hippocampal mossy fibers in mediating the behaviorally-sensitizing effects of NIC. Outbred rats were phenotype-screened as high-responders (HR; locomotor reactivity to novelty score ranking in the upper third of the population) or low-responders (LR; locomotor reactivity to novelty score ranking in the lower third of the population). In Experiment 1, both phenotypes were trained with four NIC injections (at 3-d intervals on postnatal days 33-44), and lidocaine microinfusion was used to temporarily inactivate the hippocampal hilus at each NIC injection. Systemic saline and microinjection of artificial cerebral spinal fluid (CSF) were used as controls. During NIC training, lidocaine inactivation caused augmented locomotor response to NIC in HRs compared to LRs irrespective of injection days. Following 1 week of abstinence, all animals were challenged with a low dose of NIC. During challenge, previously NIC/CSF trained LRs and HRs were divided into two; one half receiving lidocaine inactivation of the hippocampal hilus and the other half receiving CSF control microinjection. Only HRs showed behavioral sensitization to the challenge dose of NIC, which was enhanced with lidocaine inactivation. In Experiment 2, a single NIC exposure was found sufficient to induce sensitization to the challenge dose of NIC in HRs, and concurrently an enlarged supra-pyramidal mossy fiber (SP-MF) terminal field. The increase in the SP-MF volume in HRs was greater with repeated NIC training. In both single and repeated NIC training cases, a significant positive morphobehavioral correlation was observed between challenge NIC-induced locomotion and the SP-MF terminal field volume. These findings suggest that the HR hippocampal mossy fibers are vulnerable to neuroadaptive alterations induced by NIC, which may be a substrate for the observed behavioral vulnerability to NIC.

Evidence of reuptake inhibition responsible for mecamylamine-evoked increases in extracellular serotonin.

The present report using microdialysis approach investigates the neurochemical mechanism of mecamylamine in the regulation of extracellular serotonin in the dorsal raphe nucleus of freely behaving rats. These results suggest that mecamylamine may block serotonin reuptake, the effect consistent with its efficacy of antidepressant.

Delayed effects of chronic variable stress during peripubertal-juvenile period on hippocampal morphology and on cognitive and stress axis functions in rats.

Animal studies on the effects of chronic variable stress during the peripubertal-juvenile period on hippocampal structure and function are lacking. Twenty-eight-day-old Sprague-Dawley rats were subjected to random, variable physical or social stress regimens for 4 weeks. Hippocampal volume was found to continue to grow in all lamina examined during the transition into young adulthood. Our variable physical stress paradigm led to inhibition of this growth in the CA1 pyramidal cell layer (PCL) and in the dentate gyrus-granular cell layer (DG-GCL), which reached full arrest in the CA3-PCL. Volume deficits were first observed after chronic stress exposure when 3 weeks, but not 24 h, of recovery had elapsed. Moreover, these volume deficits were associated with impairments in the Morris water-maze navigation, sustained down-regulation in the basal hippocampal glucocorticoid receptor gene expression, and deficits in the shutdown of acute stress-induced corticosterone secretion. Volume changes both due to normal maturation and after chronic stress exposure were independent of neuron number. Thus, a peripubertal-juvenile chronic stress paradigm that leads to significant alterations in the limbic-hypothalamic-pituitary-adrenal axis can produce robust effects in hippocampal structure and cognitive ability, lasting into adulthood.

Hippocampal mossy fibre terminal field size is differentially affected in a rat model of risk-taking behaviour.

Individual differences in novelty-induced exploratory activity identify rats which can serve as a model of human sensation-seeking, risk-taking behaviour. Experimentally naïve rats, when exposed to mild stress of a novel environment, exhibit variability in their exploratory activity. Some rats display high rates of locomotor reactivity to novelty (high responders (HR)), and others display low rates (low responders (LR)). The LRHR phenotype is a reliable predictor of drug-taking behaviour and is linked to differences in hippocampal glucocorticoid receptor mRNA expression. In this study, we investigated whether the LRHR phenotype is associated with differences in the quantitative morphology of the hippocampal field CA3, dentate gyrus molecular layer, granule cell layer and mossy fibres. LRs and HRs showed no significant differences in the volumes of CA3 and dentate molecular layer volume or the number of dentate granule cells. However, LRs had a significantly larger suprapyramidal mossy fibre terminal field volume when compared to HRs. The infrapyramidal mossy fibres did not differ between phenotypes. Also, we found a LRHR phenotype-independent significant negative correlation between molecular layer volume per granule cell and the total number of granule cells. These findings implicate the SP-MF in vulnerability for risk-taking behaviour, and we propose that LR and HR hippocampi may differ in the way novelty information is processed.

The delta-opioid receptor agonist (+)BW373U86 regulates BDNF mRNA expression in rats.

delta-Opioid receptor agonists have antidepressant-like effects in behavioral models of depression. Chronic administration of classical antidepressants upregulates mRNA expression of brain-derived neurotrophic factor (BDNF) and its high-affinity tyrosine kinase receptor, TrkB in the frontal cortex and hippocampus of rats. Increases in BDNF and TrkB levels are thought to be important for the therapeutic effects of these drugs. Therefore, we examined the ability of the delta-opioid receptor agonist (+)BW373U86 to regulate BDNF and TrkB mRNA expression in frontal cortex, hippocampus, as well as, basolateral amygdala, endopiriform nucleus, and primary olfactory cortex. At 3 h after a single administration of (+)BW373U86 animals were killed and BDNF and TrkB mRNA levels were examined by in situ hybridization. BDNF mRNA levels produced by (+)BW373U86 were compared to acute administration of the antidepressants desipramine and bupropion. A behaviorally antidepressant dose of 10 mg/kg (+)BW373U86 increased BDNF mRNA expression in all regions examined; a smaller dose of (+)BW373U86 (1 mg/kg) significantly increased BDNF mRNA expression only in frontal cortex. The delta-opioid receptor antagonist naltrindole blocked (+)BW373U86-mediated increases in BDNF mRNA expression. In addition, tolerance developed to increased BDNF mRNA expression with repeated injection, except in frontal cortex. Midazolam was administered to some animals to prevent the convulsions produced by (+)BW373U86, but midazolam did not block delta-opioid receptor-mediated increases in BDNF mRNA expression in frontal cortex, hippocampus, or amygdala. Unlike desipramine and bupropion, (+)BW373U86 upregulated BDNF mRNA expression acutely (within 3 h after a single administration). These data support the concept that delta-opioid receptor agonists may have antidepressant potential, and could be good targets for the development of faster-acting antidepressants.

Colocalization of estrogen beta-receptor messenger RNA with orphanin FQ, vasopressin and oxytocin in the rat hypothalamic paraventricular and supraoptic nuclei.

The functional significance of the novel estrogen receptor beta in brain areas that exclusively contain the ERbeta receptor subtype such as the paraventricular (PVN) and the supraoptic (SON) nuclei of the hypothalamus is not yet fully understood. The present study attempts to characterize the peptidergic nature of the ERbeta-containing neuronal population in the PVN and the SON using the double in situ histochemistry method in the female rat. Using this method, the ERbeta mRNA coexpressions with the novel opioid neuropeptide (orphanin FQ and its receptor ORL1) mRNA in addition to the previously reported neuropeptide (arginine vasopressin-AVP, oxytocin-OXY, corticotropin releasing hormone-CRH, enkephalin-ENK) mRNAs were assessed. In the PVN, roughly half of the ERbeta expression was colocalized with the prepro-orphanin FQ mRNA, which was comparable to the colocalization observed between the ERbeta and AVP mRNAs in the same region. In addition, there was 20% overlap between the ERbeta and ORL1 receptor mRNAs, and 10% overlap between the ERbeta and OXY mRNAs in the PVN. By contrast, the coexpression between the prepro-orphanin FQ and ERbeta mRNAs was less striking in the SON. Potential interactions between the ERbeta and the well-characterized AVP-OXY neurosecretory system as well as the novel OFQ-ORL1 opioid neuropeptide system may provide new leads for the functional significance of ERbeta, specifically in stress/autonomic responses.

Effects of neonatal gonadal steroids on adult CA3 pyramidal neuron dendritic morphology and spatial memory in rats.

The hippocampus is implicated in spatial cognition, which is sexually dimorphic and developmentally sensitive to gonadal steroids. Previously we have shown a sex difference in CA3 pyramidal cell layer volume and neuronal soma size that was reversible with neonatal castration in males or prenatal treatment of females with either testosterone propionate (TP) or a nonaromatizable androgen, dihydrotestosterone propionate, but not estradiol benzoate, all of which correlated with adult water maze navigation. The present study further investigates developmental androgen sensitivity of CA3 pyramidal neurons by measuring dendritic morphology and its relation to adult spatial ability. Female rats were injected with TP on postnatal day (P) 3 and P5 or ovariectomized (OVX) on P2, and male rats were castrated on P2, with or without testosterone replacement (Cas+T). Sham surgery controls were also included. Animals were tested on a water maze in adulthood, sacrificed, and CA3 pyramidal neurons were Golgi-stained and reconstructed in three dimensions using a computer-interfaced morphometry system. High-androgen groups (control males, Cas+T, TP females) performed better in spatial navigation and exhibited CA3 neurons with longer dendrites, a larger number of dendritic branches, and volumes of influence compared to low-androgen groups (control females, castrated males, OVX). Collectively, these findings indicate that the critical time period for organizational effects of androgens on the CA3 pyramidal neurons includes both prenatal and postnatal life, during which time androgens regulate developmental events such as somal growth and neuronal differentiation, all of which significantly contribute to establishing the sex difference in adult spatial navigation.

Correlation of estrogen beta-receptor messenger RNA with endogenous levels of plasma estradiol and progesterone in the female rat hypothalamus, the bed nucleus of stria terminalis and the medial amygdala.

Estrogen receptor beta (ERbeta) has been previously mapped in the rat central nervous system. This study aims to explore the regulation of ERbeta mRNA as it is expressed in the intact and cycling female rat brain. Young adult female rats (90+ day, N=20) were screened for estrous phases via vaginal cytology and sacrificed. Brains and blood were collected and processed for in situ hybridization and estradiol (E2) and progesterone (P4) hormone assays, respectively. ERbeta mRNA levels exhibited significant correlations with ovarian steroid ratios (E2/P4) in various brain regions, including the bed nucleus of stria terminalis, the medial nucleus of amygdala, and the anteroventral periventricular nuclei but not the paraventricular and the supraoptic nuclei or the preoptic area of the hypothalamus. No regulatory changes were detected in the cortex. Specifically, in the affected regions, higher P4 levels were significantly correlated with higher ERbeta mRNA expression. In contrast, there was a tendency for higher E2 levels to be correlated with lower ERbeta mRNA expression, but this tendency reached significance only in the bed nucleus of stria terminalis. These results suggest that ERbeta mRNA is regulated in the intact and cycling female rat hypothalamic as well as extrahypothalamic brain regions, and the circulating ovarian hormones play a critical role.