Adolescent morphine exposure impairs cognitive flexibility in female but not male mice.

Use of prescription opioids continues to rise, especially in adolescent individuals. As adolescence is a critical development window for higher order cognitive functions, thus opioid exposure during this period may have significant long-lasting effects on cognitive function and predisposition individuals to be at greater risk of developing opioid use later in life. Here, we examine previously explored effects of opioid exposure during adolescence on affect-related behavior, motivation, and cognitive flexibility. We find that a two-week exposure to non-contingent morphine during adolescence (i.e., post-weaning) does not alter performance in an elevated plus maze, forced swim test, or motivation for appetitive reward in male or female mice when tested during adolescence or adulthood. Examination of how adolescent morphine impacts cognition revealed impairments in visual-based discriminative learning and cognitive flexibility in female but not male mice, as assessed using an operant-based attentional set-shifting task. Unexpectedly, deficits in discriminative learning are observed when testing occurred during adolescence but not adulthood, whereas impaired performance in the extradimensional shift remained impaired into adulthood. The data indicate that opioid exposure during adolescence has a greater impact on cognitive function in female mice and that these deficits may be more widespread during acute withdrawal periods, while deficits in flexibility more enduring.

Infralimbic cortex pyramidal neuron GIRK signaling contributes to regulation of cognitive flexibility but not affect-related behavior in male mice.

Dysfunction of the infralimbic cortical (ILC) region of the medial prefrontal cortex (mPFC) is thought to be an underlying factor in both affect- and cognition-related behavioral deficits that co-occur across neuropsychiatric disorders. Increasing evidence highlights pathological imbalances in prefrontal pyramidal neuron excitability and associated aberrant firing as an underlying factor in this dysfunction. G protein-gated inwardly rectifying K+ (GIRK/Kir3) channels mediate excitability of mPFC pyramidal neurons, however the functional role of these channels in ILC-dependent regulation of behavior and pyramidal neuron excitation is unknown. The present study used a viral-cre approach in male mice harboring a 'floxed' version of the kcnj3 (Girk1) gene, to disrupt GIRK1-containing channel expression in pyramidal neurons within the ILC. Loss of GIRK1-dependent signaling increased excitability and spike firing of pyramidal neurons but did not alter affective behavior measured in an elevated plus maze, forced swim test, or progressive ratio test of motivation. Alternatively, ablation of GIRK1 impaired performance in an operant-based attentional set-shifting task designed to assess cognitive flexibility. These data highlight a unique role for GIRK1 signaling in ILC pyramidal neurons in the regulation of strategy shifting but not affect and suggest that these channels may represent a therapeutic target for treatment of cognitive deficits in neuropsychiatric disease.

Suppression of pyramidal neuron G protein-gated inwardly rectifying K+ channel signaling impairs prelimbic cortical function and underlies stress-induced deficits in cognitive flexibility in male, but not female, mice.

Imbalance in prefrontal cortical (PFC) pyramidal neuron excitation:inhibition is thought to underlie symptomologies shared across stress-related disorders and neuropsychiatric disease, including dysregulation of emotion and cognitive function. G protein-gated inwardly rectifying K+ (GIRK/Kir3) channels mediate excitability of medial PFC pyramidal neurons, however, the functional role of these channels in mPFC-dependent regulation of affect, cognition, and cortical dynamics is unknown. We used a viral-cre approach in male and female mice harboring a "floxed" version of the kcnj3 (Girk1) gene, to disrupt GIRK1-containing channel expression in pyramidal neurons within the prelimbic cortex (PrL). In males, loss of pyramidal GIRK1-dependent signaling differentially impacted measures of affect and impaired working memory and cognitive flexibility. Unexpectedly, ablation of PrL GIRK1-dependent signaling did not impact affect or cognition in female mice. Additional studies used a model of chronic unpredictable stress (CUS) to determine the impact on PrL GIRK-dependent signaling and cognitive function. CUS exposure in male mice produced deficits in cognition that paralleled a reduction in PrL pyramidal GIRK-dependent signaling akin to viral approaches whereas CUS exposure in female mice did not alter cognitive flexibility performance. Stress-induced behavioral deficits in male mice were rescued by systemic injection of a novel, GIRK1-selective agonist, ML297. In conclusion, GIRK1-dependent signaling in male mice, but not females, is critical for maintaining optimal PrL function and behavioral control. Disruption of this inhibition may underlie stress-related dysfunction of the PrL and represent a therapeutic target for treating stress-induced deficits in affect regulation and impaired cognition that reduce quality of life.

Remifentanil self-administration in mice promotes sex-specific prefrontal cortex dysfunction underlying deficits in cognitive flexibility.

Opioid-based drugs are frequently used for pain management in both males and females despite the known risk of prefrontal cortex dysfunction and cognitive impairments. Although poorly understood, loss of cognitive control following chronic drug use has been linked to decreased activation of frontal cortex regions. Here, we show that self-administration of the potent opioid, remifentanil, causes a long-lasting hypoactive basal state evidenced by a decrease in ex vivo excitability that is paralleled by an increase in firing capacity of layer 5/6 pyramidal neurons in the prelimbic, but not infralimbic region of the medial prefrontal cortex. This phenomenon was observed in females after as few as 5 days and up to 25-30 days of self-administration. In contrast, pyramidal neurons in males showed increased excitability following 10-16 days of self-administration, with hypoactive states arising only following 25-30 days of self-administration. The emergence of a hypoactive, but not hyperactive basal state following remifentanil self-administration aligned with deficits in cognitive flexibility as assessed using an operant-based attentional set-shifting task. In females, the hypoactive basal state is driven by a reduction in excitatory synaptic transmission mediated by AMPA-type glutamate receptors. Alternatively, hyper- and hypoactive states in males align selectively with decreased and increased GABAB signaling, respectively. Chemogenetic compensation for this hypoactive state prior to testing restored cognitive flexibility, basal hypoactive state, and remifentanil-induced plasticity. These data define cellular and synaptic mechanisms by which opioids impair prefrontal function and cognitive control; indicating that interventions aimed at targeting opioid-induced adaptations should be tailored based on biological sex.

Estradiol Regulation of the Prelimbic Cortex and the Reinstatement of Cocaine Seeking in Female Rats.

Relapse susceptibility in women with substance use disorders (SUDs) has been linked to the estrogen, 17ß-estradiol (E2). Our previous findings in female rats suggest that the influence of E2 on cocaine seeking can be localized to the prelimbic prefrontal cortex (PrL-PFC). Here, we investigated the receptor mechanisms through which E2 regulates the reinstatement of extinguished cocaine seeking. Sexually mature female rats underwent intravenous cocaine self-administration (0.5 mg/inf; 14 × 2 h daily) and extinction, and then were ovariectomized before reinstatement testing. E2 (10 µg/kg, i.p.) alone did not reinstate cocaine seeking, but it potentiated reinstatement when combined with an otherwise subthreshold priming dose of cocaine. A similar effect was observed following intra-PrL-PFC microinfusions of E2 and by systemic or intra-PrL-PFC administration of the estrogen receptor (ER)ß agonist, DPN, but not agonists at ERα or the G-protein-coupled ER1 (GPER1). By contrast, E2-potentiated reinstatement was prevented by intra-PrL-PFC microinfusions of the ERß antagonist, MPP, or the GPER1 antagonist, G15, but not an ERα antagonist. Whole-cell recordings in PrL-PFC layer (L)5/6 pyramidal neurons revealed that E2 decreases the frequency, but not amplitude, of GABAA-dependent miniature IPSCs (mIPSC). As was the case with E2-potentiated reinstatement, E2 reductions in mIPSC frequency were prevented by ERß and GPER1, but not ERα, antagonists and mimicked by ERß, but not GPER1, agonists. Altogether, the findings suggest that E2 activates ERß and GPER1 in the PrL-PFC to attenuate the GABA-mediated constraint of key outputs that mediate cocaine seeking.

The Role of Parvalbumin Interneuron GIRK Signaling in the Regulation of Affect and Cognition in Male and Female Mice.

Pathological impairments in the regulation of affect (i.e., emotion) and flexible decision-making are commonly observed across numerous neuropsychiatric disorders and are thought to reflect dysfunction of cortical and subcortical circuits that arise in part from imbalances in excitation and inhibition within these structures. Disruptions in GABA transmission, in particular, that from parvalbumin-expressing interneurons (PVI), has been highlighted as a likely mechanism by which this imbalance arises, as they regulate excitation and synchronization of principle output neurons. G protein-gated inwardly rectifying potassium ion (GIRK/Kir3) channels are known to modulate excitability and output of pyramidal neurons in areas like the medial prefrontal cortex and hippocampus; however, the role GIRK plays in PVI excitability and behavior is unknown. Male and female mice lacking GIRK1 in PVI (Girk1flox/flox:PVcre) and expressing td-tomato in PVI (Girk1flox/flox:PVCre:PVtdtom) exhibited increased open arm time in the elevated plus-maze, while males showed an increase in immobile episodes during the forced swim test (FST). Loss of GIRK1 did not alter motivated behavior for an appetitive reward or impair overall performance in an operant-based attention set-shifting model of cognitive flexibility; however it did alter types of errors committed during the visual cue test. Unexpectedly, baseline sex differences were also identified in these tasks, with females exhibiting overall poorer performance compared to males and distinct types of errors, highlighting potential differences in task-related problem-solving. Interestingly, reductions in PVI GIRK signaling did not correspond to changes in membrane excitability but did increase action potential (AP) firing at higher current injections in PVI of males, but not females. This is the first investigation on the role that PVI GIRK-signaling has on membrane excitability, AP firing, and their role on affect and cognition together increasing the understanding of PVI cellular mechanisms and function.

Acute Blockade of PACAP-Dependent Activity in the Ventromedial Nucleus of the Hypothalamus Disrupts Leptin-Induced Behavioral and Molecular Changes in Rats.

Leptin signaling pathways, stemming primarily from the hypothalamus, are necessary for maintaining normal energy homeostasis and body weight. In both rodents and humans, dysregulation of leptin signaling leads to morbid obesity and diabetes. Since leptin resistance is considered a primary factor underlying obesity, understanding the regulation of leptin signaling could lead to therapeutic tools and provide insights into the causality of obesity. While leptin actions in some hypothalamic regions such as the arcuate nuclei have been characterized, less is known about leptin activity in the hypothalamic ventromedial nuclei (VMN). Recently, pituitary adenylate cyclase-activating polypeptide (PACAP) has been shown to reduce feeding behavior and alter metabolism when administered into the VMN in a pattern similar to that of leptin. In the current study, we examined whether leptin and PACAP actions in the VMN share overlapping pathways in the regulation of energy balance. Interestingly, PACAP administration into the VMN increased STAT3 phosphorylation and SOCS3 mRNA expression, both of which are hallmarks of leptin receptor activation. In addition, BDNF mRNA expression in the VMN was increased by both leptin and PACAP administration. Moreover, antagonizing PACAP receptors fully reversed the behavioral and cellular effects of leptin injections into the VMN. Electrophysiological studies further illustrated that leptin-induced effects on VMN neurons were blocked by antagonizing PACAP receptors. We conclude that leptin dependency on PACAP signaling in the VMN suggests a potential common signaling cascade, allowing a tonically and systemically secreted neuropeptide to be more precisely regulated by central neuropeptides.

Interaction of stress and stimulants in female rats: Role of chronic stress on later reactivity to methamphetamine.

Previous research in humans and animals suggests that prior exposure to stress alters responsivity to drugs of abuse, including psychostimulants. Male rats show an augmented striatal dopamine response to methamphetamine following exposure to chronic unpredictable stress (CUS). Compared to males, female rats have been shown to be highly sensitive to the effects of stimulants and stress independently, however few studies have examined the interaction between stress and stimulants in female rats. Therefore, the current study investigated whether prior exposure to chronic stress potentiated the behavioral and neurochemical responses to an acute injection of methamphetamine in female rats. Adult female Sprague-Dawley rats were either exposed to CUS or left undisturbed (control) and then two weeks later received an injection of 1.0 or 7.5 mg/kg methamphetamine. Based on open field findings, a subsequent group of rats were exposed to CUS or left undisturbed and then two weeks later received 7.5 mg/kg methamphetamine and either dopamine efflux in the dorsal striatum or nucleus accumbens was measured or methamphetamine and amphetamine levels were measured in the brain and plasma. Female rats exposed to CUS traveled greater distances in the open field immediately following an injection of 7.5 mg/kg, but not 1.0 mg/kg, of methamphetamine and then showed high levels or stereotypy similar to control rats. Animals exposed to CUS had significantly greater increases in dorsal striatum dopamine following an acute injection of 7.5 mg/kg methamphetamine compared to control rats, but not in the nucleus accumbens. These differences were not due to group differences in levels of methamphetamine or amphetamine in the brain or plasma. The current findings demonstrate stress-augmented neurochemical responses to a dose of methamphetamine, similar to that self-administered, which increases understanding of the cross-sensitization between stress and methamphetamine in females.

Cell-type and region-specific nucleus accumbens AMPAR plasticity associated with morphine reward, reinstatement, and spontaneous withdrawal.

Despite evidence that morphine-related pathologies reflect adaptations in NAc glutamate signaling, substantial gaps in basic information remain. The current study examines the impact of non-contingent acute, repeated, and withdrawal-inducing morphine dosing regimens on glutamate transmission in D1- or D2-MSNs in the nucleus accumbens shell (NAcSh) and core (NAcC) sub-regions in hopes of identifying excitatory plasticity that may contribute to unique facets of opioid addiction-related behavior. Following an acute morphine injection (10 mg/kg), average miniature excitatory postsynaptic current (mEPSC) amplitude mediated by AMPA-type glutamate receptors was increased at D1-MSNs in the both the NAcShl and NAcC, whereas only the frequency of events was elevated at D2-MSNs in the NAcSh. In contrast, spontaneous somatic withdrawal induced by escalating dose of repeated morphine twice per day (20, 40, 60, 80, 100 mg/kg) enhanced mEPSC frequency specifically at D2-MSNs in the NAcSh. Similar to previous findings, excitatory drive was elevated at NAcSh D1-MSNs after 10-14 days home cage abstinence. Following abstinence, an acute drug re-exposure produced a rapid and enduring endocytosis of GluA2-containing AMPARs at D1-MSNs in the shell, that when blocked by an intra-NAc shell infusion of the Tat-GluA23Y peptide, increased reinstatement of morphine place preference-a phenomenon distinctly different than effects previously found with cocaine. The present study is the first to directly identify unique circuit specific adaptations in NAc glutamate synaptic transmission associated with morphine-related acute reward and somatic withdrawal as well as post-abstinence short-term plasticity. Moreover, while differing classes of abused drugs (i.e., psychostimulants and opioids) produce seemingly similar bidirectional plasticity in the NAc following drug re-exposure, our findings indicate this plasticity has distinct behavioral consequences.

Social anxiety and employment interviews: does nonverbal feedback differentially predict cortisol and performance?

BACKGROUND & OBJECTIVES: Interviewers often provide positive nonverbal feedback to reduce interviewees' anxiety. Socially anxious individuals typically harbor negative self-views discrepant with positive feedback. We examined whether nonverbal feedback and social anxiety jointly influence cortisol responses to, and performance during, interviews. DESIGN: An experimental between-subjects design randomly assigned participants to feedback condition. METHODS: Undergraduate students (N = 130) provided saliva and completed social anxiety, interview anxiety, and affective measures before a simulated interview. Following a standardized script, a confederate interviewer provided positive, ambiguous, or negative nonverbal feedback. Participants then provided saliva and completed self-focused attention and self-awareness measures. Confederate interviewers and an external rater evaluated participants' anxiety displays, assertive behavior, and performance. RESULTS: Positive feedback decreased cortisol and improved performance for low social anxiety participants. Socially anxious participants exhibited higher cortisol but did not exhibit significant differences in performance after positive compared to negative feedback. CONCLUSIONS: Consistent with previous findings, positive feedback did not benefit socially anxious interviewees. Positive feedback increased physiological arousal relative to negative feedback but did not hinder performance among people high in social anxiety. These results provide novel information about the interactive influence of social anxiety and nonverbal interviewer feedback on arousal, self-focus, and interview performance.

Negative consequences of early-life adversity on substance use as mediated by corticotropin-releasing factor modulation of serotonin activity.

Early-life adversity is associated with increased risk for substance abuse in later life, with women more likely to report past and current stress as a mediating factor in their substance use and relapse as compared to men. Preclinical models of neonatal and peri-adolescent (early through late adolescence) stress all support a direct relationship between experiences of early-life adversity and adult substance-related behaviors, and provide valuable information regarding the underlying neurobiology. This review will provide an overview of these animal models and how these paradigms alter drug and alcohol consumption and/or seeking in male and female adults. An introduction to the corticotropin-releasing factor (CRF) and serotonin systems, their development and their interactions at the level of the dorsal raphe will be provided, illustrating how this particular stress system is sexually dimorphic, and is well positioned to be affected by stressors early in development and throughout maturation. A model for CRF-serotonin interactions in the dorsal raphe and how these influence dopaminergic activity within the nucleus accumbens and subsequent reward-associated behaviors will be provided, and alterations to the activity of this system following early-life adversity will be identified. Overall, converging findings suggest that early-life adversity has long-term effects on the functioning of the CRF-serotonin system, highlighting a potentially important and targetable mediator linking stress to addiction. Future work should focus on identifying the exact mechanisms that promote long-term changes to the expression and activity of CRF receptors in the dorsal raphe. Moreover, it is important to clarify whether similar neurobiological mechanisms exist for males and females, given the sexual dimorphism both in CRF receptors and serotonin indices in the dorsal raphe and in the behavioral outcomes of early-life adversity.

Social isolation alters central nervous system monoamine content in prairie voles following acute restraint.

Animal models have shown that social isolation and other forms of social stress lead to depressive- and anxiety-relevant behaviors, as well as neuroendocrine and physiological dysfunction. The goal of this study was to investigate the effects of prior social isolation on neurotransmitter content following acute restraint in prairie voles. Animals were either paired with a same-sex sibling or isolated for 4 weeks. Plasma adrenal hormones and ex vivo tissue concentrations of monoamine neurotransmitters and their metabolites were measured following an acute restraint stressor in all animals. Isolated prairie voles displayed significantly increased circulating adrenocorticotropic hormone levels, as well as elevated serotonin and dopamine levels in the hypothalamus, and potentially decreased levels of serotonin in the frontal cortex. However, no group differences in monoamine levels were observed in the hippocampus or raphe. The results suggest that social stress may bias monoamine neurotransmission and stress hormone function to subsequent acute stressors, such as restraint. These findings improve our understanding of the neurobiological mechanisms underlying the consequences of social stress.

Persistent behavioral and neurochemical sensitization to an acute injection of methamphetamine following unpredictable stress.

Prior research in humans and animals suggest that exposure to chronic stress alters the response to drugs of abuse, increasing vulnerability to drug addiction. Chronic unpredictable stress (CUS) has been shown to augment the increase of dopamine in the striatum when challenged with high doses of methamphetamine immediately following stress exposure, however it is not known whether this neurochemical stress-sensitization continues after the cessation of the stressors or if behavioral sensitization is also present. Therefore, the current study examined the immediate and delayed effects of CUS on methamphetamine-induced behaviors and striatal dopamine levels. Male rats were exposed to 10 days of CUS and then tested in either an open field box to assess locomotion or underwent in vivo microdialysis to measure striatal dopamine levels immediately following CUS or after a 1-2 week delay. All rats exposed to CUS showed a potentiated locomotor response immediately following an acute injection of 7.5mg/kg methamphetamine compared to non-stressed control rats. Both groups of CUS rats also showed augmented dopamine release and rectal temperatures following methamphetamine with prolonged increases in the CUS rats tested after a delay. These results suggest that CUS increases the sensitivity of a rat to a single injection of methamphetamine and that the increased sensitivity persists for up to 2 weeks following the last stressor.