Central oxytocinergic neurons can likely modulate stress-related circuits through both paracrine ... more Central oxytocinergic neurons can likely modulate stress-related circuits through both paracrine and synaptic release of oxytocin (OT). One classic hallmark of a stress response is the activation o...
The anti-depressant-like effects of Mucuna pruriens (MP) were studied in validated models of depr... more The anti-depressant-like effects of Mucuna pruriens (MP) were studied in validated models of depression. Psycho-pharmacological investigations involved acute and chronic treatment (14 days) of mucuna in forced swim test (FST), tail suspension test (TST) in mice and olfactory bulbectomy in rats, respectively. Dose response study in mice FST and TST revealed the initial anti-depressant-like effect of Mucuna (10-20 mg/kg i.p.). Interaction studies revealed that, mucuna (10 mg/kg) significantly enhanced the anti-depressant action of fluoxetine and bupropion in FST and TST respectively. Potentiation of 5-Hydroxytryptophan induced head twitches response (in mice) and reversal of reserpine induced hypothermia (rats) were observed at same dose level. Further, the behaviour anomalies exhibited by olfactory bulbectomised rats (OBX) were attenuated by chronic mucuna treatment as observed in open field. In conclusion, this behavioural study depicts the anti-depressant-like effect of mucuna in a...
Neuroimmune signaling is increasingly identified as a critical component of various illnesses, in... more Neuroimmune signaling is increasingly identified as a critical component of various illnesses, including chronic pain, substance use disorder, and depression. However, the underlying neural mechanisms remain unclear. Proinflammatory cytokines, such as tumor necrosis factor-α (TNF-α), may play a key role by modulating synaptic function and long-term plasticity. The midbrain structure periaqueductal gray (PAG) plays a well-established role in pain processing, and while TNF-α inhibitors have emerged as a potential therapeutic strategy for pain-related disorders, the impact of TNF-α on PAG neuronal activity has not been thoroughly characterized. Recent studies have identified subpopulations of ventral PAG (vPAG) with opposing effects on nociception, with DA neurons driving pain relief in contrast to GABA neurons. Therefore, we used ex vivo slice physiology to examine the effects of TNF-α on neuronal activity of both subpopulations. We selectively targeted GABA and dopamine neurons using...
Significant prior evidence indicates that centrally acting oxytocin robustly modulates stress res... more Significant prior evidence indicates that centrally acting oxytocin robustly modulates stress responsiveness and anxiety‐like behaviour, although the neural mechanisms behind these effects are not entirely understood. A plausible neural basis for oxytocin‐mediated stress reduction is via inhibition of corticotrophin‐releasing hormone (CRH) neurones in the paraventricular nucleus of the hypothalamus (PVN) that regulate activation of the hypothalamic‐pituitary‐adrenal axis. Previously, we have shown that, following s.c. injection of 2.0 mol L−1 NaCl, oxytocin synthesising neurones are activated in the rat PVN, an oxytocin receptor (Oxtr)‐dependent inhibitory tone develops on a subset of parvocellular neurones and stress‐mediated increases in plasma corticosterone levels are blunted. In the present study, we utilised transgenic male CRH‐reporter mice to selectively target PVN CRH neurones for whole‐cell recordings. These experiments reveal that acute salt loading produces tonic inhibition of PVN CRH neurones through a mechanism that is largely independent of synaptic activity. Further studies reveal that a subset of CRH neurones within the PVN synthesise mRNA for Oxtr(s). Salt induced Oxtr‐dependent inhibitory tone was eliminated in individual PVN CRH neurones filled with GDP‐β‐S. Additional electrophysiological studies suggest that reduced excitability of PVN CRH neurones in salt‐loaded animals is associated with increased activation of inwardly rectifying potassium channels. Nevertheless, substantial effort to recapitulate the core effects of salt loading by activating Oxtr(s) with an exogenous agonist produced mixed results. Collectively, these results enhance our understanding of how oxytocin receptor‐mediated signalling modulates the function of CRH neurones in the PVN.
High salt diet can reduce anxiety-like behavior and, yet can also promote hypertension. Previous ... more High salt diet can reduce anxiety-like behavior and, yet can also promote hypertension. Previous work from our lab has shown that mild transient increase in plasma sodium and osmolality can elevate the central levels of oxytocin which can then act on pathways that mediate stress responsiveness and anxiety-like behavior. Here, we used CRF reporter mice to discern the central oxytocinergic pathways associated with heightened stress responsiveness. For all the experiments, animals were rendered osmotically dehydrated and testing was conducted 1 hour after the injections to ensure elevated central levels of oxytocin. The degree of hypernatremia was assessed by measuring plasma sodium concentration (pNa+) and osmolality (pOsm) following injections of either 2.0 M NaCl or 0.15 M NaCl. Restraint was used as a psychogenic stressor to determine the effect of hypernatremia on the plasma corticosterone levels as well as patterns of neuronal activation. Anxiety-like behavior was studied using t...
Neuroimmune signaling is increasingly identified as a critical component of various illnesses, in... more Neuroimmune signaling is increasingly identified as a critical component of various illnesses, including chronic pain, substance use disorder, and depression. However, the underlying neural mechanisms remain unclear. Proinflammatory cytokines, such as tumor necrosis factor-α (TNF-α), may play a role by modulating synaptic function and long-term plasticity. The midbrain structure periaqueductal gray (PAG) plays a well-established role in pain processing, and while TNF-α inhibitors have emerged as a therapeutic strategy for pain-related disorders, the impact of TNF-α on PAG neuronal activity has not been thoroughly characterized. Recent studies have identified subpopulations of ventrolateral PAG (vlPAG) with opposing effects on nociception, with dopamine (DA) neurons driving pain relief in contrast to GABA neurons. Therefore, we used slice physiology to examine the impact of TNF-α on neuronal activity of both these subpopulations. We focused on female mice since the PAG is a sexually ...
Alcohol use disorder is complex and multi-faceted, involving the engagement of multiple signaling... more Alcohol use disorder is complex and multi-faceted, involving the engagement of multiple signaling systems across numerous brain regions to drive pathological behavior. Previous work has indicated that both the insular cortex and dynorphin (DYN)/Kappa opioid receptor (KOR) systems contribute to excessive alcohol use. More recently, we identified a microcircuit in the medial aspect of the insular cortex that signals through DYN/KOR. Here, we explored the role of insula DYN/KOR circuit elements on alcohol intake in a long-term intermittent access (IA) procedure. Using a combination of conditional knockout strategies and site-directed pharmacology, we discovered distinct and sex-specific roles for insula DYN and KOR systems in alcohol drinking and related behavior. Our findings show that insula DYN deletion blocked escalated consumption and decreased overall intake of and preference for alcohol in male and female mice. This effect was specific to alcohol in male mice, as DYN deletion di...
As an integrative hub, the insular cortex (IC) translates external cues into interoceptive states... more As an integrative hub, the insular cortex (IC) translates external cues into interoceptive states that generate complex physiological, affective, and behavioral responses. However, the precise circuit and signaling mechanisms in the IC that modulate these processes are unknown. Here, we describe a midbrain-projecting microcircuit in the medial aspect of the agranular IC that signals through the Gαi/o-coupled kappa opioid receptor (KOR) and its endogenous ligand dynorphin (Dyn). Within this microcircuit, Dyn is robustly expressed in layer 2/3, while KOR is localized to deep layer 5, which sends a long-range projection to the substantia nigra (SN). Using ex vivo electrophysiology, we evaluated the functional impact of KOR signaling in layer 5 of the IC. We found that bath application of dynorphin decreased GABA release and increased glutamate release by IC-SN neurons, but did not alter their excitability. Conversely, dynorphin decreased the excitability of GABA neurons without altering synaptic transmission. Pretreatment with the KOR antagonist nor-BNI blocked the effects of dynorphin on IC-SN neurons and GABA neurons, indicating that the changes in synaptic transmission and excitability were selectively mediated through KOR. Selective inhibition of IC GABA neurons using a KOR-derived DREADD recapitulated these effects. This work provides insight into IC microcircuitry and indicates that Dyn/KOR signaling may act to directly reduce activity of layer 5 GABA neurons. In turn, KOR-driven inhibition of GABA promotes disinhibition of IC-SN neurons, which can modulate downstream circuits. Our findings present a potential mechanism whereby chronic upregulation of IC Dyn/KOR signaling can lead to altered subcortical function and downstream activity.
Neuroadaptations in brain regions that regulate emotional and reward-seeking behaviors have been ... more Neuroadaptations in brain regions that regulate emotional and reward-seeking behaviors have been suggested to contribute to pathological behaviors associated with alcohol-use disorder. One such region is the bed nucleus of the stria terminalis (BNST), which has been linked to both alcohol consumption and alcohol withdrawal-induced anxiety and depression. Recently, we identified a GABAergic microcircuit in the BNST that regulates anxiety-like behavior. In the present study, we examined how chronic alcohol exposure alters this BNST GABAergic microcircuit in mice. We selectively targeted neurons expressing corticotropin releasing factor (CRF) using a CRF-reporter mouse line and combined retrograde labeling to identify BNST projections to the ventral tegmental area (VTA) and lateral hypothalamus (LH). Following 72 h of withdrawal from four weekly cycles of chronic intermittent ethanol (CIE) vapor exposure, the excitability of a sub-population of putative local CRF neurons that did not project to either VTA or LH (CRFnon-VTA/LH neurons) was increased. Withdrawal from CIE also increased excitability of non-CRF BNST neurons that project to both LH and VTA (BNSTnon-CRF-proj neurons). Furthermore, both populations of neurons had a reduction in spontaneous EPSC amplitude while frequency was unaltered. Withdrawal from chronic alcohol was accompanied by a significant increase in spontaneous IPSC frequency selectively in the BNSTnon-CRF-proj neurons. Together, these data suggest that withdrawal from chronic ethanol dysregulates local CRF-GABAergic microcircuit to inhibit anxiolytic outputs of the BNST which may contribute to enhanced anxiety during alcohol withdrawal and drive alcohol-seeking behavior.
The United States is experiencing an opioid epidemic of significant proportions, imposing enormou... more The United States is experiencing an opioid epidemic of significant proportions, imposing enormous fiscal and societal costs. While prescription opioid analgesics are essential for treating pain, the cessation of these drugs can induce a withdrawal syndrome, and thus opioid use often persists to alleviate or avoid these symptoms. Therefore, it is essential to understand the neurobiology underlying this critical window of withdrawal from opioid analgesics to prevent continued usage. To model this, we administered a low dose of morphine, and precipitated withdrawal with naloxone to investigate the behavioral and cellular responses in C57BL/6J male and female mice. Following 3 days of administration, both male and female mice sensitized to the repeated bouts of withdrawal, as evidenced by their composite global withdrawal score. Female mice exhibited increased withdrawal symptoms on some individual measures, but did not show characteristic weight loss observed in male mice. Because of ...
ABSTRACTAcute exposure to a salient stressor, such as in post-traumatic stress disorder, can have... more ABSTRACTAcute exposure to a salient stressor, such as in post-traumatic stress disorder, can have lasting impacts upon an individual and society. To study stress in rodents, some naturalistic methods have included acute exposure to a predator odor, such as the synthetized fox odor 2,4,5, trimethyl-3-thiazoline (TMT). These experiments explore the stress-related behaviors and cortical activity induced by TMT exposure in adult male C57BL/6J mice and the influence of the stress neuropeptide, corticotropin-releasing factor (CRF) on these responses. Compared to H2O, mice exposed to TMT in the home cage showed increased avoidance and defensive burying indicative of evident stress responses. Consistent with stress-induced activation of the medial prefrontal cortex (mPFC), we found that the prelimbic (PL) and infralimbic (IL) subregions of the mPFC had elevated c-Fos immunolabeling after TMT compared to H2O. Slice physiology recordings were performed in layers 2/3 and 5 of the PL and IL, fo...
The United States is experiencing an opioid crisis imposing enormous fiscal and societal costs an... more The United States is experiencing an opioid crisis imposing enormous fiscal and societal costs and driving the staggering overdose death rate. While prescription opioid analgesics are essential for treating acute pain, cessation of use in individuals with a physical dependence induces an aversive withdrawal syndrome that promotes continued drug use to alleviate/avoid these symptoms. Additionally, repeated bouts of withdrawal often lead to an increased propensity for relapse. Understanding the neurobiology underlying withdrawal is essential for providing novel treatment options to alleviate physiological and affective components accompanying the cessation of opiate use. Here, we administered morphine and precipitated withdrawal with naloxone to investigate behavioral and cellular responses in C57BL/6J male and female mice. Following 3 days of administration, both male and female mice demonstrated sensitized withdrawal symptoms. Since the bed nucleus of the stria terminalis (BNST) plays a role in mediating withdrawal‐associated behaviors, we examined plastic changes in inhibitory synaptic transmission within this structure 24 hours following the final precipitated withdrawal. In male mice, morphine withdrawal increased spontaneous GABAergic signaling compared with controls. In contrast, morphine withdrawal decreased spontaneous GABAergic signaling in female mice. Intriguingly, these opposing GABAergic effects were contingent upon activity‐dependent dynamics within the ex vivo slice. Our findings suggest that male and female mice exhibit some divergent cellular responses in the BNST following morphine withdrawal, and alterations in BNST inhibitory signaling may contribute to the expression of behaviors following opioid withdrawal.
Stress can drive adaptive changes to maintain survival during threatening stimuli. Chronic stress... more Stress can drive adaptive changes to maintain survival during threatening stimuli. Chronic stress exposure, however, may result in pathological adaptations. A key neurotransmitter involved in stress signaling is norepinephrine. Previous studies show that acute stress elevates norepinephrine levels in the bed nucleus of the stria terminalis (BNST), a critical node regulating anxiety and upstream of stress responses. Here, we use mice expressing channelrhodopsin in norepinephrine neurons to selectively activate terminals in the BNST, and measure norepinephrine release with optogenetics-assisted fast-scan cyclic voltammetry (FSCV). We demonstrate that while corticosterone habituates to chronic restraint stress, cFos activation of medullary norepinephrine neurons shows equivalent activation under both acute and chronic stress conditions. Mice exposed to a single restraint session show an identical optically stimulated norepinephrine release profile compared to that of unexposed mice. Mice experiencing 5 days of restraint stress, however, show elevated norepinephrine release across multiple stimulation parameters, and reduced sensitivity to the α2-adrenergic receptor (AR) antagonist idazoxan. These data are the first to examine norepinephrine release in the BNST to tonic and phasic stimulation frequencies, and confirm that repeated stress alters autoreceptor sensitivity.
Significant prior evidence indicates that centrally acting oxytocin robustly modulates stress res... more Significant prior evidence indicates that centrally acting oxytocin robustly modulates stress responsiveness and anxiety-like behavior, although the neural mechanisms behind these effects are not completely understood. A plausible neural basis for oxytocin mediated stress reduction is via inhibition of corticotropin-releasing hormone (CRH) neurons in the paraventricular nucleus of the hypothalamus (PVN) that regulate activation of the hypothalamic-pituitary-adrenal (HPA) axis. Previously, we have shown that following subcutaneous injection of 2.0 M NaCl, oxytocin (OT) synthesizing neurons are activated in the rat PVN, an oxytocin receptor (Oxtr) dependent inhibitory tone develops on a subset of parvocellular neurons, and stress-mediated increases in plasma corticosterone levels are blunted. Here, we utilized transgenic male CRH-reporter mice to selectively target PVN CRH neurons for whole-cell recordings. These experiments reveal that acute salt loading produces tonic inhibition of ...
The N-methyl--aspartate receptor (NMDAR) is mechanistically involved in the behavioral and neurop... more The N-methyl--aspartate receptor (NMDAR) is mechanistically involved in the behavioral and neurophysiological effects of alcohol, but the specific role of the GluN2A subunit remains unclear. Here, we exposed mice with constitutive GluN2A gene knockout (KO) to chronic intermittent ethanol vapor (CIE) and tested for EtOH consumption/preference using a two-bottle choice paradigm, as well as NMDAR-mediated transmission at basolateral amygdala synapses via ex vivo slice electrophysiology. Results showed that GluN2A KO mice attained comparable blood EtOH levels in response to CIE exposure, but did not exhibit the significant increase in EtOH drinking that was observed in CIE-exposed wildtypes. GluN2A KO mice also showed no alterations in BLA NMDAR-mediated synaptic transmission after CIE, relative to air-exposed, whereas C57BL/6 J mice showed an attenuated synaptic response to GluN2B antagonism. Taken together, these data add to mounting evidence supporting GluN2A-containing NMDARs as a m...
Central oxytocinergic neurons can likely modulate stress-related circuits through both paracrine ... more Central oxytocinergic neurons can likely modulate stress-related circuits through both paracrine and synaptic release of oxytocin (OT). One classic hallmark of a stress response is the activation o...
The anti-depressant-like effects of Mucuna pruriens (MP) were studied in validated models of depr... more The anti-depressant-like effects of Mucuna pruriens (MP) were studied in validated models of depression. Psycho-pharmacological investigations involved acute and chronic treatment (14 days) of mucuna in forced swim test (FST), tail suspension test (TST) in mice and olfactory bulbectomy in rats, respectively. Dose response study in mice FST and TST revealed the initial anti-depressant-like effect of Mucuna (10-20 mg/kg i.p.). Interaction studies revealed that, mucuna (10 mg/kg) significantly enhanced the anti-depressant action of fluoxetine and bupropion in FST and TST respectively. Potentiation of 5-Hydroxytryptophan induced head twitches response (in mice) and reversal of reserpine induced hypothermia (rats) were observed at same dose level. Further, the behaviour anomalies exhibited by olfactory bulbectomised rats (OBX) were attenuated by chronic mucuna treatment as observed in open field. In conclusion, this behavioural study depicts the anti-depressant-like effect of mucuna in a...
Neuroimmune signaling is increasingly identified as a critical component of various illnesses, in... more Neuroimmune signaling is increasingly identified as a critical component of various illnesses, including chronic pain, substance use disorder, and depression. However, the underlying neural mechanisms remain unclear. Proinflammatory cytokines, such as tumor necrosis factor-α (TNF-α), may play a key role by modulating synaptic function and long-term plasticity. The midbrain structure periaqueductal gray (PAG) plays a well-established role in pain processing, and while TNF-α inhibitors have emerged as a potential therapeutic strategy for pain-related disorders, the impact of TNF-α on PAG neuronal activity has not been thoroughly characterized. Recent studies have identified subpopulations of ventral PAG (vPAG) with opposing effects on nociception, with DA neurons driving pain relief in contrast to GABA neurons. Therefore, we used ex vivo slice physiology to examine the effects of TNF-α on neuronal activity of both subpopulations. We selectively targeted GABA and dopamine neurons using...
Significant prior evidence indicates that centrally acting oxytocin robustly modulates stress res... more Significant prior evidence indicates that centrally acting oxytocin robustly modulates stress responsiveness and anxiety‐like behaviour, although the neural mechanisms behind these effects are not entirely understood. A plausible neural basis for oxytocin‐mediated stress reduction is via inhibition of corticotrophin‐releasing hormone (CRH) neurones in the paraventricular nucleus of the hypothalamus (PVN) that regulate activation of the hypothalamic‐pituitary‐adrenal axis. Previously, we have shown that, following s.c. injection of 2.0 mol L−1 NaCl, oxytocin synthesising neurones are activated in the rat PVN, an oxytocin receptor (Oxtr)‐dependent inhibitory tone develops on a subset of parvocellular neurones and stress‐mediated increases in plasma corticosterone levels are blunted. In the present study, we utilised transgenic male CRH‐reporter mice to selectively target PVN CRH neurones for whole‐cell recordings. These experiments reveal that acute salt loading produces tonic inhibition of PVN CRH neurones through a mechanism that is largely independent of synaptic activity. Further studies reveal that a subset of CRH neurones within the PVN synthesise mRNA for Oxtr(s). Salt induced Oxtr‐dependent inhibitory tone was eliminated in individual PVN CRH neurones filled with GDP‐β‐S. Additional electrophysiological studies suggest that reduced excitability of PVN CRH neurones in salt‐loaded animals is associated with increased activation of inwardly rectifying potassium channels. Nevertheless, substantial effort to recapitulate the core effects of salt loading by activating Oxtr(s) with an exogenous agonist produced mixed results. Collectively, these results enhance our understanding of how oxytocin receptor‐mediated signalling modulates the function of CRH neurones in the PVN.
High salt diet can reduce anxiety-like behavior and, yet can also promote hypertension. Previous ... more High salt diet can reduce anxiety-like behavior and, yet can also promote hypertension. Previous work from our lab has shown that mild transient increase in plasma sodium and osmolality can elevate the central levels of oxytocin which can then act on pathways that mediate stress responsiveness and anxiety-like behavior. Here, we used CRF reporter mice to discern the central oxytocinergic pathways associated with heightened stress responsiveness. For all the experiments, animals were rendered osmotically dehydrated and testing was conducted 1 hour after the injections to ensure elevated central levels of oxytocin. The degree of hypernatremia was assessed by measuring plasma sodium concentration (pNa+) and osmolality (pOsm) following injections of either 2.0 M NaCl or 0.15 M NaCl. Restraint was used as a psychogenic stressor to determine the effect of hypernatremia on the plasma corticosterone levels as well as patterns of neuronal activation. Anxiety-like behavior was studied using t...
Neuroimmune signaling is increasingly identified as a critical component of various illnesses, in... more Neuroimmune signaling is increasingly identified as a critical component of various illnesses, including chronic pain, substance use disorder, and depression. However, the underlying neural mechanisms remain unclear. Proinflammatory cytokines, such as tumor necrosis factor-α (TNF-α), may play a role by modulating synaptic function and long-term plasticity. The midbrain structure periaqueductal gray (PAG) plays a well-established role in pain processing, and while TNF-α inhibitors have emerged as a therapeutic strategy for pain-related disorders, the impact of TNF-α on PAG neuronal activity has not been thoroughly characterized. Recent studies have identified subpopulations of ventrolateral PAG (vlPAG) with opposing effects on nociception, with dopamine (DA) neurons driving pain relief in contrast to GABA neurons. Therefore, we used slice physiology to examine the impact of TNF-α on neuronal activity of both these subpopulations. We focused on female mice since the PAG is a sexually ...
Alcohol use disorder is complex and multi-faceted, involving the engagement of multiple signaling... more Alcohol use disorder is complex and multi-faceted, involving the engagement of multiple signaling systems across numerous brain regions to drive pathological behavior. Previous work has indicated that both the insular cortex and dynorphin (DYN)/Kappa opioid receptor (KOR) systems contribute to excessive alcohol use. More recently, we identified a microcircuit in the medial aspect of the insular cortex that signals through DYN/KOR. Here, we explored the role of insula DYN/KOR circuit elements on alcohol intake in a long-term intermittent access (IA) procedure. Using a combination of conditional knockout strategies and site-directed pharmacology, we discovered distinct and sex-specific roles for insula DYN and KOR systems in alcohol drinking and related behavior. Our findings show that insula DYN deletion blocked escalated consumption and decreased overall intake of and preference for alcohol in male and female mice. This effect was specific to alcohol in male mice, as DYN deletion di...
As an integrative hub, the insular cortex (IC) translates external cues into interoceptive states... more As an integrative hub, the insular cortex (IC) translates external cues into interoceptive states that generate complex physiological, affective, and behavioral responses. However, the precise circuit and signaling mechanisms in the IC that modulate these processes are unknown. Here, we describe a midbrain-projecting microcircuit in the medial aspect of the agranular IC that signals through the Gαi/o-coupled kappa opioid receptor (KOR) and its endogenous ligand dynorphin (Dyn). Within this microcircuit, Dyn is robustly expressed in layer 2/3, while KOR is localized to deep layer 5, which sends a long-range projection to the substantia nigra (SN). Using ex vivo electrophysiology, we evaluated the functional impact of KOR signaling in layer 5 of the IC. We found that bath application of dynorphin decreased GABA release and increased glutamate release by IC-SN neurons, but did not alter their excitability. Conversely, dynorphin decreased the excitability of GABA neurons without altering synaptic transmission. Pretreatment with the KOR antagonist nor-BNI blocked the effects of dynorphin on IC-SN neurons and GABA neurons, indicating that the changes in synaptic transmission and excitability were selectively mediated through KOR. Selective inhibition of IC GABA neurons using a KOR-derived DREADD recapitulated these effects. This work provides insight into IC microcircuitry and indicates that Dyn/KOR signaling may act to directly reduce activity of layer 5 GABA neurons. In turn, KOR-driven inhibition of GABA promotes disinhibition of IC-SN neurons, which can modulate downstream circuits. Our findings present a potential mechanism whereby chronic upregulation of IC Dyn/KOR signaling can lead to altered subcortical function and downstream activity.
Neuroadaptations in brain regions that regulate emotional and reward-seeking behaviors have been ... more Neuroadaptations in brain regions that regulate emotional and reward-seeking behaviors have been suggested to contribute to pathological behaviors associated with alcohol-use disorder. One such region is the bed nucleus of the stria terminalis (BNST), which has been linked to both alcohol consumption and alcohol withdrawal-induced anxiety and depression. Recently, we identified a GABAergic microcircuit in the BNST that regulates anxiety-like behavior. In the present study, we examined how chronic alcohol exposure alters this BNST GABAergic microcircuit in mice. We selectively targeted neurons expressing corticotropin releasing factor (CRF) using a CRF-reporter mouse line and combined retrograde labeling to identify BNST projections to the ventral tegmental area (VTA) and lateral hypothalamus (LH). Following 72 h of withdrawal from four weekly cycles of chronic intermittent ethanol (CIE) vapor exposure, the excitability of a sub-population of putative local CRF neurons that did not project to either VTA or LH (CRFnon-VTA/LH neurons) was increased. Withdrawal from CIE also increased excitability of non-CRF BNST neurons that project to both LH and VTA (BNSTnon-CRF-proj neurons). Furthermore, both populations of neurons had a reduction in spontaneous EPSC amplitude while frequency was unaltered. Withdrawal from chronic alcohol was accompanied by a significant increase in spontaneous IPSC frequency selectively in the BNSTnon-CRF-proj neurons. Together, these data suggest that withdrawal from chronic ethanol dysregulates local CRF-GABAergic microcircuit to inhibit anxiolytic outputs of the BNST which may contribute to enhanced anxiety during alcohol withdrawal and drive alcohol-seeking behavior.
The United States is experiencing an opioid epidemic of significant proportions, imposing enormou... more The United States is experiencing an opioid epidemic of significant proportions, imposing enormous fiscal and societal costs. While prescription opioid analgesics are essential for treating pain, the cessation of these drugs can induce a withdrawal syndrome, and thus opioid use often persists to alleviate or avoid these symptoms. Therefore, it is essential to understand the neurobiology underlying this critical window of withdrawal from opioid analgesics to prevent continued usage. To model this, we administered a low dose of morphine, and precipitated withdrawal with naloxone to investigate the behavioral and cellular responses in C57BL/6J male and female mice. Following 3 days of administration, both male and female mice sensitized to the repeated bouts of withdrawal, as evidenced by their composite global withdrawal score. Female mice exhibited increased withdrawal symptoms on some individual measures, but did not show characteristic weight loss observed in male mice. Because of ...
ABSTRACTAcute exposure to a salient stressor, such as in post-traumatic stress disorder, can have... more ABSTRACTAcute exposure to a salient stressor, such as in post-traumatic stress disorder, can have lasting impacts upon an individual and society. To study stress in rodents, some naturalistic methods have included acute exposure to a predator odor, such as the synthetized fox odor 2,4,5, trimethyl-3-thiazoline (TMT). These experiments explore the stress-related behaviors and cortical activity induced by TMT exposure in adult male C57BL/6J mice and the influence of the stress neuropeptide, corticotropin-releasing factor (CRF) on these responses. Compared to H2O, mice exposed to TMT in the home cage showed increased avoidance and defensive burying indicative of evident stress responses. Consistent with stress-induced activation of the medial prefrontal cortex (mPFC), we found that the prelimbic (PL) and infralimbic (IL) subregions of the mPFC had elevated c-Fos immunolabeling after TMT compared to H2O. Slice physiology recordings were performed in layers 2/3 and 5 of the PL and IL, fo...
The United States is experiencing an opioid crisis imposing enormous fiscal and societal costs an... more The United States is experiencing an opioid crisis imposing enormous fiscal and societal costs and driving the staggering overdose death rate. While prescription opioid analgesics are essential for treating acute pain, cessation of use in individuals with a physical dependence induces an aversive withdrawal syndrome that promotes continued drug use to alleviate/avoid these symptoms. Additionally, repeated bouts of withdrawal often lead to an increased propensity for relapse. Understanding the neurobiology underlying withdrawal is essential for providing novel treatment options to alleviate physiological and affective components accompanying the cessation of opiate use. Here, we administered morphine and precipitated withdrawal with naloxone to investigate behavioral and cellular responses in C57BL/6J male and female mice. Following 3 days of administration, both male and female mice demonstrated sensitized withdrawal symptoms. Since the bed nucleus of the stria terminalis (BNST) plays a role in mediating withdrawal‐associated behaviors, we examined plastic changes in inhibitory synaptic transmission within this structure 24 hours following the final precipitated withdrawal. In male mice, morphine withdrawal increased spontaneous GABAergic signaling compared with controls. In contrast, morphine withdrawal decreased spontaneous GABAergic signaling in female mice. Intriguingly, these opposing GABAergic effects were contingent upon activity‐dependent dynamics within the ex vivo slice. Our findings suggest that male and female mice exhibit some divergent cellular responses in the BNST following morphine withdrawal, and alterations in BNST inhibitory signaling may contribute to the expression of behaviors following opioid withdrawal.
Stress can drive adaptive changes to maintain survival during threatening stimuli. Chronic stress... more Stress can drive adaptive changes to maintain survival during threatening stimuli. Chronic stress exposure, however, may result in pathological adaptations. A key neurotransmitter involved in stress signaling is norepinephrine. Previous studies show that acute stress elevates norepinephrine levels in the bed nucleus of the stria terminalis (BNST), a critical node regulating anxiety and upstream of stress responses. Here, we use mice expressing channelrhodopsin in norepinephrine neurons to selectively activate terminals in the BNST, and measure norepinephrine release with optogenetics-assisted fast-scan cyclic voltammetry (FSCV). We demonstrate that while corticosterone habituates to chronic restraint stress, cFos activation of medullary norepinephrine neurons shows equivalent activation under both acute and chronic stress conditions. Mice exposed to a single restraint session show an identical optically stimulated norepinephrine release profile compared to that of unexposed mice. Mice experiencing 5 days of restraint stress, however, show elevated norepinephrine release across multiple stimulation parameters, and reduced sensitivity to the α2-adrenergic receptor (AR) antagonist idazoxan. These data are the first to examine norepinephrine release in the BNST to tonic and phasic stimulation frequencies, and confirm that repeated stress alters autoreceptor sensitivity.
Significant prior evidence indicates that centrally acting oxytocin robustly modulates stress res... more Significant prior evidence indicates that centrally acting oxytocin robustly modulates stress responsiveness and anxiety-like behavior, although the neural mechanisms behind these effects are not completely understood. A plausible neural basis for oxytocin mediated stress reduction is via inhibition of corticotropin-releasing hormone (CRH) neurons in the paraventricular nucleus of the hypothalamus (PVN) that regulate activation of the hypothalamic-pituitary-adrenal (HPA) axis. Previously, we have shown that following subcutaneous injection of 2.0 M NaCl, oxytocin (OT) synthesizing neurons are activated in the rat PVN, an oxytocin receptor (Oxtr) dependent inhibitory tone develops on a subset of parvocellular neurons, and stress-mediated increases in plasma corticosterone levels are blunted. Here, we utilized transgenic male CRH-reporter mice to selectively target PVN CRH neurons for whole-cell recordings. These experiments reveal that acute salt loading produces tonic inhibition of ...
The N-methyl--aspartate receptor (NMDAR) is mechanistically involved in the behavioral and neurop... more The N-methyl--aspartate receptor (NMDAR) is mechanistically involved in the behavioral and neurophysiological effects of alcohol, but the specific role of the GluN2A subunit remains unclear. Here, we exposed mice with constitutive GluN2A gene knockout (KO) to chronic intermittent ethanol vapor (CIE) and tested for EtOH consumption/preference using a two-bottle choice paradigm, as well as NMDAR-mediated transmission at basolateral amygdala synapses via ex vivo slice electrophysiology. Results showed that GluN2A KO mice attained comparable blood EtOH levels in response to CIE exposure, but did not exhibit the significant increase in EtOH drinking that was observed in CIE-exposed wildtypes. GluN2A KO mice also showed no alterations in BLA NMDAR-mediated synaptic transmission after CIE, relative to air-exposed, whereas C57BL/6 J mice showed an attenuated synaptic response to GluN2B antagonism. Taken together, these data add to mounting evidence supporting GluN2A-containing NMDARs as a m...
Uploads
Papers by Dipanwita Pati