Formation of False Context Fear Memory Is Regulated by Hypothalamic Corticotropin-Releasing Factor in Mice.

Traumatic events frequently produce false fear memories. We investigated the effect of hypothalamic corticotropin-releasing factor (CRF) knockdown (Hy-Crf-KD) or overexpression (Hy-CRF-OE) on contextual fear memory, as fear stress-released CRF and hypothalamic-pituitary-adrenal axis activation affects the memory system. Mice were placed in a chamber with an electric footshock as a conditioning stimulus (CS) in Context A, then exposed to a novel chamber without CS, as Context B, at 3 h (B-3h) or 24 h (B-24h). The freezing response in B-3h was intensified in the experimental mice, compared to control mice not exposed to CS, indicating that a false fear memory was formed at 3 h. The within-group freezing level at B-24h was higher than that at B-3h, indicating that false context fear memory was enhanced at B-24h. The difference in freezing levels between B-3h and B-24h in Hy-Crf-KD mice was larger than that of controls. In Hy-CRF-OE mice, the freezing level at B-3h was higher than that of control and Hy-Crf-KD mice, while the freezing level in B-24h was similar to that in B-3h. Locomotor activity before CS and freezing level during CS were similar among the groups. Therefore, we hypothesized that Hy-Crf-KD potentiates the induction of false context fear memory, while Hy-CRF-OE enhances the onset of false fear memory formation.

Comparative metabolic profiling of posterior parietal cortex, amygdala, and hippocampus in conditioned fear memory.

Fear conditioning and retrieval are suitable models to investigate the biological basis of various mental disorders. Hippocampus and amygdala neurons consolidate conditioned stimulus (CS)-dependent fear memory. Posterior parietal cortex is considered important for the CS-dependent conditioning and retrieval of fear memory. Metabolomic screening among functionally related brain areas provides molecular signatures and biomarkers to improve the treatment of psychopathologies. Herein, we analyzed and compared changes of metabolites in the hippocampus, amygdala, and posterior parietal cortex under the fear retrieval condition. Metabolite profiles of posterior parietal cortex and amygdala were similarly changed after fear memory retrieval. While the retrieval of fear memory perturbed various metabolic pathways, most metabolic pathways that overlapped among the three brain regions had high ranks in the enrichment analysis of posterior parietal cortex. In posterior parietal cortex, the most perturbed pathways were pantothenate and CoA biosynthesis, purine metabolism, glutathione metabolism, and NAD+ dependent signaling. Metabolites of posterior parietal cortex including 4'-phosphopantetheine, xanthine, glutathione, ADP-ribose, ADP-ribose 2'-phosphate, and cyclic ADP-ribose were significantly regulated in these metabolic pathways. These results point to the importance of metabolites of posterior parietal cortex in conditioned fear memory retrieval and may provide potential biomarker candidates for traumatic memory-related mental disorders.

Evaluation of efficiency omega 3 fatty acid improves the behavioural phenotype and protects against oxidative stress against MPP+ induces Parkinson's disease in mice.

This experiment proposed to study the efficiency omega 3 fatty acid on behavioural phenotype of Parkinson's disease (PD) in mice. Totally 7 groups (each group 6 mice) were used in this assessment, each groups were treated with saline (control), MPP+, L-DOPA, Omega 3 oil, Omega 3 oil (three different concentrations) +MPP+ separately. The behavioral assessments such as bar test, open field test, maze test, hang test were noted on 7th, 14th, 21st and 28th day. After the examination period, the tested animals' midbrains and frontal cortex were dissected to analyze TBARS, GSH, Catalase, Superoxide Dismutase and Glutathione Peroxidase assay. In the bar test, 500mg omega 3 fatty acid administrated mice showed a high cataleptic scores. In open field Test, significant reductions in behavior analysis were observed from the tested mice group. Maze test and hang test doesn't show much difference. In biochemical test, tested groups showed promising results compared to control group. The result strongly proved that the omega 3 fatty acid has remarkable abilities to control the neurodegenerative diseases.

c-Fos expression following context conditioning and deep brain stimulation in the bed nucleus of the stria terminalis in rats.

Deep brain stimulation (DBS) in the bed nucleus of the stria terminalis (BST), a region implicated in the expression of anxiety, shows promise in psychiatric patients, but its effects throughout the limbic system are largely unknown. In male Wistar rats, we first evaluated the neural signature of contextual fear (N = 16) and next, of the anxiolytic effects of high-frequency electrical stimulation in the BST (N = 31), by means of c-Fos protein expression. In non-operated animals, we found that the left medial anterior BST displayed increased c-Fos expression in anxious (i.e., context-conditioned) versus control subjects. Moreover, control rats showed asymmetric expression in the basolateral amygdala (BLA) (i.e., higher intensities in the right hemisphere), which was absent in anxious animals. The predominant finding in rats receiving bilateral BST stimulation was a striking increase in c-Fos expression throughout much of the left hemisphere, which was not confined to the predefined regions of interest. To conclude, we found evidence for lateralized c-Fos expression during the expression of contextual fear and anxiolytic high-frequency electrical stimulation of the BST, particularly in the medial anterior BST and BLA. In addition, we observed an extensive and unexpected left-sided c-Fos spread following bilateral stimulation in the BST.

Involvement of the lateral habenula in fear memory.

Increasing evidence points to the engagement of the lateral habenula (LHb) in the selection of appropriate behavioral responses in aversive situations. However, very few data have been gathered with respect to its role in fear memory formation, especially in learning paradigms in which brain areas involved in cognitive processes like the hippocampus (HPC) and the medial prefrontal cortex (mPFC) are required. A paradigm of this sort is trace fear conditioning, in which an aversive event is preceded by a discrete stimulus, generally a tone, but without the close temporal contiguity allowing for their association based on amygdala-dependent information processing. In a first experiment, we analyzed cellular activations (c-Fos expression) induced by trace fear conditioning in subregions of the habenular complex, HPC, mPFC and amygdala using a factorial analysis to unravel functional networks through correlational analysis of data. This analysis suggested that distinct LHb subregions engaged in different aspects of conditioning, e.g. associative processes and onset of fear responses. In a second experiment, we performed chemogenetic LHb inactivation during the conditioning phase of the trace fear conditioning paradigm and subsequently assessed contextual and tone fear memories. Whereas LHb inactivation did not modify rat's behavior during conditioning, it induced contextual memory deficits and enhanced fear to the tone. These results demonstrate the involvement of the LHb in fear memory. They further suggest that the LHb is engaged in learning about threatening environments through the selection of relevant information predictive of a danger.

Inhaled Lavandula angustifolia essential oil enhances extinction learning and inhibits memory updating in mice submitted to the contextual fear conditioning.

ETHNOPHARMACOLOGICAL RELEVANCE: Lavender (Lavandula angustifolia) essential oil (EO) has a long history of use in emotional illness, including anxiety disorders. Cognitive mechanisms of learning and memory play a pivotal role in the etiology and maintenance of anxiety since exposure to cues related to aversive situations induces high arousal and anticipatory anxiety. Memory become labile after its reactivation and can be modulated by reconsolidation or extinction. Inhibition of memory reconsolidation or facilitation of memory extinction may be effective in preventing or minimizing the effect of contextual cues on anticipatory anxiety. AIM OF THE STUDY: We investigated the effect of Lavandula angustifolia EO in the memory updating of conditioned contextual fear. MATERIALS AND METHODS: Adult male C57Bl6 mice were submitted to fear conditioning. Two days after conditioning the mice underwent a reactivation session in a hybrid context and were then immediately exposed to vaporized water or essential oil at concentrations of 1%, 2.5% or 5% for 3 h. Two days later, the mice were tested in the original or an altered context and their freezing behavior was measured. In addition, mice were subjected to a fear memory recovery protocol followed by a reinstatement session. RESULTS: In the contextual fear test, 1% essential oil, but not 2.5% or 5%, reduced the freezing behavior response, whereas after a reinstatement session, exposure to 1% essential oil increased the freezing behavior response. CONCLUSIONS: These results suggest that Lavandula angustifolia essential oil enhances memory extinction and, consequently, inhibits memory updating.

Mu-opioid and CB1 cannabinoid receptors of the dorsal periaqueductal gray interplay in the regulation of fear response, but not antinociception.

Evidence indicates that periaqueductal gray matter (PAG) plays an important role in defensive responses and pain control. The activation of cannabinoid type-1 (CB1) or mu-opioid (MOR) receptors in the dorsal region of this structure (dPAG) inhibits fear and facilitates antinociception induced by different aversive stimuli. However, it is still unknown whether these two receptors work cooperatively in order to achieve these inhibitory actions. This study investigated the involvement and a likely interplay between CB1 and MOR receptors localized into the dPAG on the regulation of fear-like defensive responses and antinociception (evaluated in tail-flick test) evoked by dPAG chemical stimulation with N-methyl-d-aspartate (NMDA). Before the administration of NMDA, animals were first intra-dPAG injected with the CB1 agonist ACEA (0.5 pmol), or with the MOR agonist DAMGO (0.5 pmol) in combination with the respective antagonists AM251 (CB1 antagonist, 100 pmol) or CTOP (MOR antagonist, 1 nmol). To investigate the interplay between these receptors, microinjection of CTOP was combined with ACEA, or microinjection of AM251 was combined with DAMGO. Our results showed that both the intra-PAG treatments with ACEA or DAMGO inhibited NMDA-induced freezing expression, whereas only the treatment with DAMGO increased antinociception induced with NMDA, which are completely blocked by its respective antagonists. Interestingly, the inhibitory effects of ACEA or DAMGO on freezing was blocked by CTOP and AM251, respectively, indicating a functional interaction between these two receptors in the mediation of defensive behaviors. However, this cooperative interaction was not observed during the NMDA-induced antinociception. Our findings indicate that there is a cooperative action between the MOR and CB1 receptors within the dPAG and it is involved in the mediation of NMDA-induced defensive responses. Additionally, the MORs into the dPAG are involved in the modulation of the antinociceptive effects that follow a fear-like defense-reaction induced by dPAG chemical stimulation with NMDA.

Defensive behaviors and brain regional activation changes in rats confronting a snake.

In the present study, we examined behavioral and brain regional activation changes of rats). To a nonmammalian predator, a wild rattler snake (Crotalus durissus terrificus). Accordingly, during snake threat, rat subjects showed a striking and highly significant behavioral response of freezing, stretch attend, and, especially, spatial avoidance of this threat. The brain regional activation patterns for these rats were in broad outline similar to those of rats encountering other predator threats, showing Fos activation of sites in the amygdala, hypothalamus, and periaqueductal gray matter. In the amygdala, only the lateral nucleus showed significant activation, although the medial nucleus, highly responsive to olfaction, also showed higher activation. Importantly, the hypothalamus, in particular, was somewhat different, with significant Fos increases in the anterior and central parts of the ventromedial hypothalamic nucleus (VMH), in contrast to patterns of enhanced Fos expression in the dorsomedial VMH to cat predators, and in the ventrolateral VMH to an attacking conspecific. In addition, the juxtodorsalmedial region of the lateral hypothalamus showed enhanced Fos activation, where inputs from the septo-hippocampal system may suggest the potential involvement of hippocampal boundary cells in the very strong spatial avoidance of the snake and the area it occupied. Notably, these two hypothalamic paths appear to merge into the dorsomedial part of the dorsal premammillary nucleus and dorsomedial and lateral parts of the periaqueductal gray, all of which present significant increases in Fos expression and are likely to be critical for the expression of defensive behaviors in responses to the snake threat.

Selective activation of estrogen receptors α and ß: Implications for depressive-like phenotypes in female mice exposed to chronic unpredictable stress.

The estrogen receptor (ER) mechanisms by which 17ß-estradiol influences depressive-like behaviour have primarily been investigated acutely and not within an animal model of depression. Therefore, the current study aimed to dissect the contribution of ERα and ERß to the effects of 17ß-estradiol under non-stress and chronic stress conditions. Ovariectomized (OVX) or sham-operated mice were treated chronically (47 days) with 17ß-estradiol (E2), the ERß agonist diarylpropionitrile (DPN), the ERα agonist propylpyrazole-triol (PPT), or vehicle. On day 15 of treatment, mice from each group were assigned to chronic unpredictable stress (CUS; 28 days) or non-CUS conditions. Mice were assessed for anxiety- and depressive-like behaviour and hypothalamic-pituitary-adrenal (HPA) axis function. Cytokine and chemokine levels, and postsynaptic density protein 95 were measured in the hippocampus and frontal cortex, and adult hippocampal neurogenesis was assessed. Overall, the effects of CUS were more robust that those of estrogenic treatments, as seen by increased immobility in the tail suspension test (TST), reduced PSD-95 expression, reduced neurogenesis in the ventral hippocampus, and HPA axis negative feedback dysregulation. However, we also observe CUS-dependent and -independent effects of ovarian status and estrogenic treatments. The effects of CUS on PSD-95 expression, the cytokine milieu, and in TST were largely driven by PPT and DPN, indicating that these treatments were not protective. Independent of CUS, estradiol increased neurogenesis in the dorsal hippocampus, blunted the corticosterone response to an acute stressor, and increased anxiety-like behaviour. These findings provide insights into the complexities of estrogen signaling in modulating depressive-like phenotypes under non-stress and chronic stress conditions.

Medial prefrontal and ventral hippocampal contributions to incidental context learning and memory in adolescent rats.

The Context Preexposure Facilitation Effect (CPFE) is a contextual fear conditioning (CFC) paradigm in which context learning, context-shock learning, and retrieval of contextual fear occur in three distinct phases. The medial prefrontal cortex (mPFC), dorsal hippocampus (dHPC), and ventral hippocampus (vHPC) are required for the acquisition and/or consolidation of a context representation during incidental context exposure (Heroux et al., 2017; Robinson-Drummer et al., 2016; Rudy & Matus-Amat, 2006). This exposure also induces the expression of the immediate early genes (IEGs) c-Fos, Arc, Egr-1, and Npas4 in these regions (Heroux et al., 2018, 2019). Despite these studies, it is still unclear how mPFC and vHPC contribute to incidental context learning and memory. The current study examined whether prefrontal or ventral hippocampal inactivation during context preexposure interferes with long-term context memory and IEG activity in the mPFC, vHPC, dHPC and the ventral midline thalamus (VMT, a region connected to both the mPFC and HPC). Adolescent Long-Evans rats were given intra-mPFC (Experiment 1) or intra-vHPC (Experiment 2) infusions of the GABAA receptor agonist muscimol or PBS prior to context preexposure, and then were sacrificed 30 min later and whole mPFC, dHPC, vHPC, and VMT were collected and assayed for IEG mRNA expression via qPCR. Prefrontal or ventral hippocampal inactivation during context exposure abolished subsequent post-shock and retention test freezing in behaviorally-tested littermates of the sacrificed groups. In Experiment 1, prefrontal inactivation reduced expression of c-Fos, Arc, Egr-1, and Npas4 in the mPFC, c-Fos, Arc, and Npas4 in the vHPC, and c-Fos in the VMT, to the level of behaviorally-naïve home-cage controls. Prefrontal inactivation did not alter IEG expression in the dHPC during context exposure. In Experiment 2, ventral hippocampal inactivation impaired expression of all IEGs in the mPFC, dHPC, and vHPC, with no effect in the VMT. Taken together, these results suggest that context memory processes on the preexposure day of the CPFE may depend on mPFC-vHPC circuitry not typically emphasized in studies of incidental or configural learning and memory.

d-Cycloserine and estradiol enhance fear extinction in nulliparous but not primiparous female rats.

Female reproductive experience has been shown to alter the hormonal, neurobiological and behavioural features of fear extinction, which is the laboratory basis of exposure therapy. This raises uncertainties as to whether pharmacological agents that enhance fear extinction in reproductively inexperienced females are equally effective in reproductively experienced females. The aim of the current study was therefore to compare the effects of two pharmacological enhancers of fear extinction, d-cycloserine (DCS) and estradiol, between nulliparous (virgin) and primiparous (reproductively experienced) female rats. In Experiment 1, nulliparous and primiparous females received systemic administration of either DCS or saline immediately after extinction training, and were tested for extinction recall the following day. DCS enhanced extinction recall in nulliparous females that showed low levels of freezing at the end of extinction training, but not among those that showed high levels of freezing at the end of extinction training. DCS did not enhance fear extinction in primiparous females, regardless of their level of freezing at the end of extinction training. In Experiment 2, nulliparous and primiparous female rats received systemic administration of either estradiol or vehicle prior to extinction training. Estradiol enhanced extinction recall among nulliparous females, but not primiparous females. Increasing the dose of estradiol administered prior to extinction training did not alter the outcomes in primiparous females (Experiment 3). Together, these findings suggest that reproductive status may be an important individual difference factor associated with the response to pharmacological modulators of extinction in rats. The implications of these findings for the pharmacological augmentation of exposure therapy in clinical populations are discussed.

Effect of Paeonia lactiflora, a traditional Chinese herb, on migraines based on clinical application and animal behavior analyses.

BACKGROUND: Paeonia lactiflora (PL) was widely used for pain relief, but its effects on migraine headaches remain unclear. PURPOSE: The aim of the present study was to investigate the effects of PL on migraine headaches. METHODS: First, we found that PL was frequently used in Taiwan for headache treatment based on data from Taiwan's National Health Insurance Research Database. Migraine was induced through the intraperitoneal injection (i.p.) of nitroglycerin (NTG, 10 mg/kg) in rats. Pretreatment with PL was administered orally 30 min prior to the NTG i.p. Migraine headache behavior was observed by video-recordings. Finally, the rats were sacrificed and brain was removed for immunohistochemistry staining analysis. RESULTS: The frequency and total time spent rearing up and sniffing in exploratory behavior, and walking in locomotor behavior, were reduced in the NTG group compared with the control group (all p <  0.001). This reduction could be ameliorated by pretreatment with PL 1.0 g/kg (all p <  0.05). Total time spent in the light chamber was lower in the NTG group compared with the control group (p <  0.05); this could be ameliorated by pretreatment with 1.0 g/kg PL (p <  0.05). The rats in the NTG group spent longer time on the smooth surface than those in the control group (p <  0.001); this could be shortened by pretreatment with 0.5 and 1.0 g/kg PL (both p <  0.01). The traveling distance of rats in the NTG group was shorter than in the control group (p <  0.001); rats given 1.0 g/kg PL had a longer traveling distance than those in the NTG group (p <  0.01). Both c-fos and CGRP immunoreactive cells increased in the TNC in the NTG group compared with that of the control group (both p <  0.001); this increased could be reduced by pretreatment with PL 0.5 and 1.0 g/kg (both p <  0.05). CONCLUSION: Pretreatment with PL ameliorated migraine headache behaviors in the NTG-induced migraine rat model, suggesting pretreatment with PL is beneficial for migraine headache treatment. This effect of PL is related to the decrease of c-fos and CGRP in the TNC. However, still there are too many methodological limitations which need to be overcome in further experiments to support the data.

Localization of Contextual and Context Removed Auditory Fear Memory within the Basolateral Amygdala Complex.

Debilitating and persistent fear memories can rapidly form in humans following exposure to traumatic events. Fear memories can also be generated and studied in animals via Pavlovian fear conditioning. The current study was designed to evaluate basolateral amygdala complex (BLC) involvement following the formation of different fear memories (two contextual fear memories and one adjusted auditory fear memory). Fear memories were created in the same context with five 1.0 mA (0.50 s) foot-shocks and, where necessary, five auditory tones (5 kHz, 75 dB, 20 s). The adjusted auditory fear conditioning protocol was employed to remove background contextual fear and produce isolated auditory fear memories. Immunofluorescent labeling was utilized to identify neurons expressing immediate early genes (IEGs). We found the two contextual fear conditioning (CFC) procedures to produce similar levels of fear-related freezing to context. Contextual fear memories produced increases in BLC IEG expression with distinct and separate patterns of expression. These data suggest contextual fear memories created in slightly altered contexts, can produce unique patterns of amygdala activation. The adjusted auditory fear conditioning procedure produced memories to a tone, but not to a context. This group, where no contextual fear was present, had a significant reduction in BLC IEG expression. These data suggest background contextual fear memories, created in standard auditory fear conditioning protocols, contribute significantly to increases in amygdala activation.

ErbB4 Receptors in the Medial Habenula Regulate Contextual Fear Memory.

The Medial Habenular (MHb) and the Lateral Habenular nuclei are 2 main parts of the habenular complex (Hb). Recent studies showed that MHb plays an important role in memory, and in the expression of ErbB4. However, the expression of MHb ErbB4 receptor and its role in fear memory is not well understood. In this study, western blotting and quantitative real-time polymerase chain reaction were used to assess the protein and mRNA levels of ErbB4 in the process of contextual fear conditioning. A pharmacological approach was used to block and stimulate the ErbB4 receptor. Contextual fear conditioning tests induced a significant increase on the expression of ErbB4 at various times in the Hb and the MHb. Moreover, the blockade and stimulation of MHb ErbB4 receptors did not affect the fear formation but impaired and improved the contextual-dependent fear expression. Furthermore, in vitro electrophysiological recordings showed that the blockade of the MHb ErbB4 receptor reduced the presynaptic gamma-amino butyric acid release. ErbB4 is a susceptible gene for schizophrenia and the above findings may provide new insights into the mechanisms of fear-related responses.

Prefrontal projections to the thalamic nucleus reuniens mediate fear extinction.

The thalamic nucleus reuniens (RE) receives dense projections from the medial prefrontal cortex (mPFC), interconnects the mPFC and hippocampus, and may serve a pivotal role in regulating emotional learning and memory. Here we show that the RE and its mPFC afferents are critical for the extinction of Pavlovian fear memories in rats. Pharmacological inactivation of the RE during extinction learning or retrieval increases freezing to an extinguished conditioned stimulus (CS); renewal of fear outside the extinction context was unaffected. Suppression of fear in the extinction context is associated with an increase in c-fos expression and spike firing in RE neurons to the extinguished CS. The role for the RE in suppressing extinguished fear requires the mPFC, insofar as pharmacogenetically silencing mPFC to RE projections impairs the expression of extinction memory. These results reveal that mPFC-RE circuits inhibit the expression of fear, a function that is essential for adaptive emotional regulation.

Neurocircuitry of fear extinction in adult and juvenile rats.

In contrast to adult rodents, juvenile rodents fail to show relapse following extinction of conditioned fear. Using different retrograde tracers injected into the infralimbic cortex (IL) and the ventral hippocampus (vHPC) in conjunction with c-Fos and parvalbumin (PV) immunochemistry, we investigated the neurocircuitry of extinction in juvenile and adult rats. Regardless of fear extinction or retrieval, juvenile rats had more c-Fos+ neurons in the basolateral amygdala (BLA) compared to adults, and showed a higher proportion of c-Fos+ IL-projecting neurons. Adult rats had more activated vHPC-projecting BLA neurons following extinction compared to retrieval, a difference not observed in juvenile rats. The number of activated vHPC- or IL-projecting BLA neurons was significantly correlated with freezing levels in adult, but not juvenile, rats. We also identified activated neurons in the BLA that simultaneously project to the IL and vHPC in the retrieval groups at both ages. This study provides novel insight into the neural process underlying extinction, especially in the juvenile period.

Fatty acid-binding proteins 5 and 7 gene deletion increases sucrose consumption and diminishes forced swim immobility time.

Inhibition and genetic deletion of fatty acid-binding proteins (FABPs) 5 and 7 have been shown to increase the levels of the endocannabinoid anandamide as well as the related N-acylethanolamine's palmitoylethanolamide and oleoylethanolamide. This study examined the role of these FABPs on forced-swim (FS) behavior and on sucrose consumption in two experiments: (experiment 1) using wild-type (WT) mice treated with the FABP inhibitor SBFI26 or vehicle and (experiment 2) using WT and FABP5/7 deficient mice. Results from experiment 1 showed that acute treatment with SBFI26 did not have any effect on sucrose intake or FS behavior in mice. In experiment 2, male and female FABP5/7 deficient mice showed significant increases in sucrose consumption (25 and 21%, respectively) compared with their WT counterparts. In addition, immobility time during the FS was decreased by 27% in both male and female FABP5/7 knockout mice compared with their WT counterparts. The fact that such differences were seen between the acute pharmacological approach and the genetic approach (gene deletion) of FABP needs to be further investigated. The function of FABPs and their specific effects on endocannabinoid anandamide, oleoylethanolamide, and palmitoylethanolamide may play an important role in the development of reward and mood behaviors and could provide opportunities for potential therapeutic targets.

Characterization of Behavioral, Signaling and Cytokine Alterations in a Rat Neurodevelopmental Model for Schizophrenia, and Their Reversal by the 5-HT6 Receptor Antagonist SB-399885.

Post-weaning social isolation of rats produces neuroanatomical, neurochemical and behavioral alterations resembling some core features of schizophrenia. This study examined the ability of the 5-HT6 receptor antagonist SB-399885 to reverse isolation-induced cognitive deficits, then investigated alterations in hippocampal cell proliferation and hippocampal and frontal cortical expression of selected intracellular signaling molecules and cytokines. Male Lister hooded rats (weaned on post-natal days 21-24 and housed individually or in groups of 3-4) received six i.p. injections of vehicle (1% Tween 80, 1 mL/kg) or SB-399885 (5 or 10 mg/kg) over a 2-week period starting 40 days post-weaning, on the days that locomotor activity, novel object discrimination (NOD), pre-pulse inhibition of acoustic startle and acquisition, retention and extinction of a conditioned freezing response (CFR) were assessed. Tissue was collected 24 h after the final injection for immunohistochemistry, reverse-phase protein microarray and western blotting. Isolation rearing impaired NOD and cue-mediated CFR, decreased cell proliferation within the dentate gyrus, and elevated hippocampal TNFα levels and Cdc42 expression. SB-399885 reversed the NOD deficit and partially normalized CFR and cell proliferation. These effects were accompanied by altered expression of several members of the c-Jun N-terminal Kinase (JNK) and p38 MAPK signaling pathways (including TAK1, MKK4 and STAT3). Although JNK and p38 themselves were unaltered at this time point hippocampal TAK1 expression and phosphorylation correlated with visual recognition memory in the NOD task. Continued use of this neurodevelopmental model could further elucidate the neurobiology of schizophrenia and aid assessment of novel therapies for drug-resistant cognitive symptoms.

Acute Stress Persistently Alters Locus Coeruleus Function and Anxiety-like Behavior in Adolescent Rats.

Stress is a physiological state characterized by altered neuroendocrine signaling, behavioral arousal, and anxiety. Chronic or traumatic stress may predispose individuals for multiple somatic and psychiatric illnesses. The locus coeruleus (LC) is a major node in the stress response that integrates input from multiple stress responsive neural circuits and releases norepinephrine (NE) throughout the central nervous system (CNS) to promote vigilance and anxiety. Many mood disorders associated with prior stress are characterized by chronically altered noradrenergic signaling, yet the long-term impact of an acute stressor on LC function is not clear. To determine how acute stress could affect anxiety-like behavior as well as LC function at immediate and extended time points, rats underwent simultaneous exposure to physical restraint and predator odor. Rats underwent behavioral testing immediately or one week after stressor exposure and were then sacrificed for whole-cell patch-clamp recordings of LC neurons. Stress caused an immediate increase in anxiety-like behaviors in the elevated plus maze (EPM), as well decreased excitatory synaptic transmission and increased spontaneous discharge in LC neurons. These effects persisted for seven days after stress. Importantly, the excitability of LC neurons was increased one week post-stress, but not immediately after, suggesting a long-term adaptation by the system. Rats tested in the open field one week after stress also showed increased anxiety-like behaviors. These findings show that a single acute stressor is capable of precipitating long-lasting changes in the LC function that may be related to some of the behavioral effects of stress, potentially contributing to stress-induced disease pathogenesis.

Effects of stressor controllability on transcriptional levels of c-fos, Arc, and brain-derived neurotrophic factor in mouse amygdala and medial prefrontal cortex.

Controllability is an important factor in determining stress outcomes. Uncontrollable stress is associated with the development of psychopathology such as post-traumatic stress disorder, whereas controllable stress is associated with adaptive stress responses and positive outcomes. In this study, we investigated how controllability affects poststress neurobiology by assessing transcriptional levels of activity-dependent genes in medial prefrontal cortex (mPFC) and amygdala, regions important in mediating stress outcomes. Mice were subjected to either escapable shock (ES) or yoked inescapable shock (IS) as models of controllable and uncontrollable stress, respectively. Immediately (0 h) or at 2 h after shock training (20 trials; 0.5 mA, 5.0 s maximum duration; 1.0 min interstimulus interval), mice were killed, and we interrogated expression levels of the immediate-early genes, c-fos and Arc, and a delayed primary response gene, brain-derived neurotrophic factor, in mPFC, amygdala, and somatosensory cortex (a control region), using real-time reverse transcription quantitative PCR (RT qPCR). We found ES-associated up-regulation of brain-derived neurotrophic factor in amygdala as well as in mPFC. IS suppressed c-fos in mPFC (0 h) but induced more Arc in amygdala (2 h) in comparison with ES. Freezing, an index of fear memory, and serum level corticosterone, an index of the stress response, did not differ between mice trained with ES or IS. The data are discussed with respect to the potential functional involvements of the amygdala and mPFC in mediating differential outcomes of controllable and uncontrollable stress.