Sex differences in dopamine release regulation in the striatum

Dopamine transmission at D1 and D2 receptors in the nucleus accumbens contributes to the expression of incubation of cocaine craving

Relapse represents a consistent clinical problem for individuals with substance use disorder. In the incubation of craving model of persistent craving and relapse, cue-induced drug seeking progressively intensifies or "incubates" during the first weeks of abstinence from drug self-administration and then remains high for months. Previously, we and others have demonstrated that expression of incubated cocaine craving requires strengthening of excitatory synaptic transmission in the nucleus accumbens core (NAcc). However, despite the importance of dopaminergic signaling in the NAcc for motivated behavior, little is known about the role that dopamine (DA) plays in the incubation of cocaine craving. Here we used fiber photometry to measure DA transients in the NAcc of male and female rats during cue-induced seeking tests conducted in early abstinence from cocaine self-administration, prior to incubation, and late abstinence, after incubation of craving has plateaued. We observed DA transients time-locked to cue-induced responding but their magnitude did not differ significantly when measured during early versus late abstinence seeking tests. Next, we tested for a functional role of these DA transients by injecting DA receptor antagonists into the NAcc just before the cue-induced seeking test. Blockade of either D1 or D2 DA receptors reduced cue-induced cocaine seeking after but not before incubation. We found no main effect of sex or significant interaction of sex with other factors in our experiments. These results suggest that DA contributes to incubated cocaine seeking but the emergence of this role reflects changes in postsynaptic responsiveness to DA rather than presynaptic alterations.

Applying the Research Domain Criteria to Rodent Studies of Sex Differences in Chronic Stress Susceptibility

Women have a 2-fold increased rate of stress-associated psychiatric disorders such as depression and anxiety, but the mechanisms that underlie this increased susceptibility remain incompletely understood. Historically, female subjects were excluded from preclinical studies and clinical trials. Additionally, chronic stress paradigms used to study psychiatric pathology in animal models were developed for use in males. However, recent changes in National Institutes of Health policy encourage inclusion of female subjects, and considerable work has been performed in recent years to understand biological sex differences that may underlie differences in susceptibility to chronic stress-associated psychiatric conditions. Here, we review the utility as well as current challenges of using the framework of the National Institute of Mental Health's Research Domain Criteria as a transdiagnostic approach to study sex differences in rodent models of chronic stress including recent progress in the study of sex differences in the neurobehavioral domains of negative valence, positive valence, cognition, social processes, and arousal.

Deciphering the genetic interplay between depression and dysmenorrhea: a Mendelian randomization study

BACKGROUND

This study aims to explore the link between depression and dysmenorrhea by using an integrated and innovative approach that combines genomic, transcriptomic, and protein interaction data/information from various resources.

METHODS

A two-sample, bidirectional, and multivariate Mendelian randomization (MR) approach was applied to determine causality between dysmenorrhea and depression. Genome-wide association study (GWAS) data were used to identify genetic variants associated with both dysmenorrhea and depression, followed by colocalization analysis of shared genetic influences. Expression quantitative trait locus (eQTL) data were analyzed from public databases to pinpoint target genes in relevant tissues. Additionally, a protein-protein interaction (PPI) network was constructed using the STRING database to analyze interactions among identified proteins.

RESULTS

MR analysis confirmed a significant causal effect of depression on dysmenorrhea ['odds ratio' (95% confidence interval) = 1.51 (1.19, 1.91), P = 7.26 × 10-4]. Conversely, no evidence was found to support a causal effect of dysmenorrhea on depression (P = .74). Genetic analysis, using GWAS and eQTL data, identified single-nucleotide polymorphisms in several genes, including GRK4, TRAIP, and RNF123, indicating that depression may impact reproductive function through these genetic pathways, with a detailed picture presented by way of analysis in the PPI network. Colocalization analysis highlighted rs34341246(RBMS3) as a potential shared causal variant.

CONCLUSIONS

This study suggests that depression significantly affects dysmenorrhea and identifies key genes and proteins involved in this interaction. The findings underline the need for integrated clinical and public health approaches that screen for depression among women presenting with dysmenorrhea and suggest new targeted preventive strategies.

The aporetic dialogues of Modena on gender differences: Is it all about testosterone? EPISODE I: CRIME

This is the first episode of a series of four discussions on the differences between males and females, in apparently non-andrological fields. You will read the transcript of discussions that actually took place at the Endocrinology Unit in Modena, Italy, in the form of the aporetic dialogues of ancient Greece. In this episode, the role of testosterone in gender differences in criminal behavior will be explored. The discussants were divided into two groups: group 1, which supports the thesis of a predominant role of testosterone, and group 2, which opposes it. The first group affirmed that both endogenous testosterone and anabolic-androgenic steroids could trigger aggressive and criminal behavior, regardless of predisposition to psychiatric disease or sociocultural background. The second group asserted the multifactorial genesis of aggressive and criminal behavior, citing other hormonal and non-hormonal factors, such as neurotransmitters, cortisol, and sociological and psychological aspects. In the end, a forensic physician, acting as a referee, tried to resolve the aporia: are the two theories equivalent or one is superior?

G protein-coupled receptor modulation of striatal dopamine transmission: Implications for psychoactive drug effects

Dopamine transmission in the striatum is a critical mediator of the rewarding and reinforcing effects of commonly misused psychoactive drugs. G protein-coupled receptors (GPCRs) that bind a variety of neuromodulators including dopamine, endocannabinoids, acetylcholine and endogenous opioid peptides regulate dopamine release by acting on several components of dopaminergic circuitry. Striatal dopamine release can be driven by both somatic action potential firing and local mechanisms that depend on acetylcholine released from striatal cholinergic interneurons. GPCRs that primarily regulate somatic firing of dopamine neurons via direct effects or modulation of synaptic inputs are likely to affect distinct aspects of behaviour and psychoactive drug actions compared with those GPCRs that primarily regulate local acetylcholine-dependent dopamine release in striatal regions. This review will highlight mechanisms by which GPCRs modulate dopaminergic transmission and the relevance of these findings to psychoactive drug effects on physiology and behaviour.

Behavioral tests of the insulin-cholinergic-dopamine link in nucleus accumbens and inhibition by high fat-high sugar diet in male and female rats

It was previously shown in striatal slices obtained from male rats that insulin excites cholinergic interneurons and increases dopamine (DA) release via α4β2 nicotinic receptors on DA terminals. The effect of insulin on DA release was blocked either by maintaining rats on a high sugar-high fat (HS-HF) diet that induced hyperinsulinemia and nucleus accumbens (NAc) insulin receptor insensitivity, or applying the α4β2 antagonist DHβE. In vivo, NAc shell insulin inactivation decreased a glucose lick microstructure parameter indicative of hedonic impact in male and female rats, and prevented flavor-nutrient learning, tested only in males. The HS-HF diet decreased hedonic impact in males but not females, and prevented flavor-nutrient learning, tested only in males. The present study extends testing to more fully assess the translation of brain slice results to the behaving rat. Insulin inactivation by antibody microinjection in NAc shell was found to decrease the number of lick bursts emitted and average lick burst size, measures of incentive motivation and hedonic impact respectively, for a wide range of glucose concentrations in male and female rats. In contrast, the HS-HF diet decreased these lick parameters in males but not females. Follow-up two-bottle choice tests for 10 % versus 40 % glucose showed decreased intake of both concentrations by males but increased intake of 40 % glucose by females. In a further set of experiments, it was predicted that α4β2 receptor blockade would induce the same behavioral effects as insulin inactivation. In females, DHβE microinjection in NAc shell decreased both lick parameters for glucose as predicted, but in males only the number of lick bursts emitted was decreased. DHβE also decreased the number of lick bursts emitted for saccharin by females but not males. Finally, DHβE microinjection in NAc shell decreased flavor-nutrient learning in both sexes. The few discrepancies seen with regard to the hypothesized insulin-nicotinic-dopaminergic regulation of behavioral responses to nutritive sweetener, and its inhibition by HS-HF diet, are discussed with reference to sex differences in DA dynamics, female resistance to diet-induced metabolic morbidities, and extra-striatal cholinergic inputs to NAc.

The ultrasonic vocalization (USV) syllable profile during neonatal opioid withdrawal and a kappa opioid receptor component to increased USV emissions in female mice

RATIONALE

Opioid use during pregnancy can lead to negative infant health outcomes, including neonatal opioid withdrawal syndrome (NOWS). NOWS comprises gastrointestinal, autonomic nervous system, and neurological dysfunction that manifest during spontaneous withdrawal. Variability in NOWS severity necessitates a more individualized treatment approach. Ultrasonic vocalizations (USVs) in neonatal mice are emitted in isolation as a stress response and are increased during opioid withdrawal, thus modeling a negative affective state that can be utilized to test new treatments.

OBJECTIVES

We sought to identify the behavioral and USV profile, brainstem transcriptomic adaptations, and role of kappa opioid receptors in USVs during neonatal opioid withdrawal.

METHODS

We employed a third trimester-approximate opioid exposure model, where neonatal inbred FVB/NJ pups were injected twice-daily with morphine (10mg/kg, s.c.) or saline (0.9%, 20 ul/g, s.c.) from postnatal day(P) 1 to P14. This protocol induces reduced weight gain, hypothermia, thermal hyperalgesia, and increased USVs during spontaneous morphine withdrawal.

RESULTS

On P14, there were increased USV emissions and altered USV syllables during withdrawal, including an increase in Complex 3 syllables in FVB/NJ females (but not males). Brainstem bulk mRNA sequencing revealed an upregulation of the kappa opioid receptor (Oprk1), which contributes to withdrawal-induced dysphoria. The kappa opioid receptor (KOR) antagonist, nor-BNI (30 mg/kg, s.c.), significantly reduced USVs in FVB/NJ females, but not males during spontaneous morphine withdrawal. Furthermore, the KOR agonist, U50,488h (0.625 mg/kg, s.c.), was sufficient to increase USVs on P10 (both sexes) and P14 (females only) in FVB/NJ mice.

CONCLUSIONS

We identified an elevated USV syllable, Complex 3, and a female-specific recruitment of the dynorphin/KOR system in increased USVs associated with neonatal opioid withdrawal severity.

Comparison of dopamine release and uptake parameters across sex, species and striatal subregions

For over four decades, fast-scan cyclic voltammetry (FSCV) has been used to selectively measure neurotransmitters such as dopamine (DA) with high spatial and temporal resolution, providing detailed information about the regulation of DA in the extracellular space. FSCV is an optimal method for determining concentrations of stimulus-evoked DA in brain tissue. When modelling diseases involving disturbances in DA transmission, preclinical rodent models are especially useful because of the availability of specialized tools and techniques that serve as a foundation for translational research. There is known heterogeneity in DA dynamics between and within DA-innervated brain structures and between males and females. However, systematic evaluations of sex- and species-differences across multiple areas are lacking. Therefore, using FSCV, we captured a broad range of DA dynamics across five sub-regions of the dorsal and ventral striatum of males and females of both rats and mice that reflect the functional heterogeneity of DA kinetics and dynamics within these structures. While numerous differences were found, in particular, we documented a strong, consistent pattern of increased DA transporter activity in females in all of the regions surveyed. The data herein are intended to be used as a resource for further investigation of DA terminal function.

The ultrasonic vocalization (USV) syllable profile during neonatal opioid withdrawal and a kappa opioid receptor component to increased USV emissions in female mice

Rationale

Opioid use during pregnancy can lead to negative infant health outcomes, including neonatal opioid withdrawal syndrome (NOWS). NOWS comprises gastrointestinal, autonomic nervous system, and neurological dysfunction that manifest during spontaneous withdrawal. Variability in NOWS severity necessitates a more individualized treatment approach. Ultrasonic vocalizations (USVs) in neonatal mice are emitted in isolation as a stress response and are increased during opioid withdrawal, thus modeling a negative affective state that can be utilized to test new treatments.

Objectives

We sought to identify the behavioral and USV profile, brainstem transcriptomic adaptations, and role of kappa opioid receptors in USVs during neonatal opioid withdrawal.

Methods

We employed a third trimester-approximate opioid exposure model, where neonatal inbred FVB/NJ pups were injected twice-daily with morphine (10mg/kg, s.c.) or saline (0.9%, 20 ul/g, s.c.) from postnatal day(P) 1 to P14. This protocol induces reduced weight gain, hypothermia, thermal hyperalgesia, and increased USVs during spontaneous morphine withdrawal.

Results

On P14, there were increased USV emissions and altered USV syllables during withdrawal, including an increase in Complex 3 syllables in FVB/NJ females (but not males). Brainstem bulk mRNA sequencing revealed an upregulation of the kappa opioid receptor (Oprk1), which contributes to withdrawal-induced dysphoria. The kappa opioid receptor (KOR) antagonist, nor-BNI (30 mg/kg, s.c.), significantly reduced USVs in FVB/NJ females, but not males during spontaneous morphine withdrawal. Furthermore, the KOR agonist, U50,488h (0.625 mg/kg, s.c.), was sufficient to increase USVs on P10 (both sexes) and P14 (females only) in FVB/NJ mice.

Conclusions

We identified an elevated USV syllable, Complex 3, and a female-specific recruitment of the dynorphin/KOR system in increased USVs associated with neonatal opioid withdrawal severity.

Male-biased vulnerability of mouse brain tryptophan/kynurenine and glutamate systems to adolescent exposures to concentrated ambient ultrafine particle air pollution

Air pollution (AP) exposures have been associated with numerous neurodevelopmental and psychiatric disorders, including autism spectrum disorder, attention deficit hyperactivity disorder and schizophrenia, all male-biased disorders with onsets from early life to late adolescence/early adulthood. While prior experimental studies have focused on effects of AP exposures during early brain development, brain development actually extends well into early adulthood. The current study in mice sought to extend the understanding of developmental brain vulnerability during adolescence, a later but significant period of brain development and maturation to the ultrafine particulate (UFPs) component of AP, considered its most reactive component. Additionally, it examined adolescent response to UFPs when preceded by earlier developmental exposures, to ascertain the trajectory of effects and potential enhancement or mitigation of adverse consequences. Outcomes focused on shared features associated with multiple neurodevelopmental disorders. For this purpose, C57Bl/6 J mice of both sexes were exposed to ambient concentrated UFPs or filtered air from PND (postnatal day) 4-7 and PND10-13, and again at PND39-42 and 45-49, resulting in 3 exposure postnatal/adolescent treatment groups per sex: Air/Air, Air/UFP, and UFP/UFP. Features common to neurodevelopmental disorders were examined at PND50. Mass exposure concentration from postnatal exposure averaged 44.34 μg/m3 and the adolescent exposure averaged 49.18 μg/m3. Male brain showed particular vulnerability to UFP exposures in adolescence, with alterations in frontal cortical and striatal glutamatergic and tryptophan/serotonergic neurotransmitters and concurrent reductions in levels of astrocytes in corpus callosum and in serum cytokine levels, with combined exposures resulting in significant reductions in corpus callosum myelination and serum corticosterone. Reductions in serum corticosterone in males correlated with reductions in neurotransmitter levels, and reductions in striatal glutamatergic function specifically correlated with reductions in corpus callosum astrocytes. UFP-induced changes in neurotransmitter levels in males were mitigated by prior postnatal exposure, suggesting potential adaptation, whereas reductions in corticosterone and in corpus callosum neuropathological effects were further strengthened by combined postnatal and adolescent exposures. UFP-induced changes in females occurred primarily in striatal dopamine systems and as reductions in serum cytokines only in response to combined postnatal and adolescent exposures. Findings in males underscore the importance of more integrated physiological assessments of mechanisms of neurotoxicity. Further, these findings provide biological plausibility for an accumulating epidemiologic literature linking air pollution to neurodevelopmental and psychiatric disorders. As such, they support a need for consideration of the regulation of the UFP component of air pollution.

Neuroplasticity-related genes correlate with individual differences in distinct phases of oxycodone self-administration in male rats

Opioid use disorder (OUD) is a chronic condition associated with long-lasting molecular and behavioral changes. Animals with prolonged access to opioids develop behaviors similar to human OUD. Identifying associated molecular changes can provide insight to underpinnings that lead to or maintain OUD. In pilot studies, we identified several miRNA targets that are altered by the administration of oxycodone. We selected mir182 for follow up as it was recently shown to be dysregulated in plasma of men administered oxycodone. In addition, mir182 is increased in reward-related brain regions of male rats following exposure to various addictive substances. The present study utilizes a long-access oxycodone self-administration paradigm to examine changes in mir182 and its mRNA targets associated with neuroplasticity, which may be involved in the maintenance of OUD-like phenotype in rats. Male rats were trained to self-administer oxycodone (0.1 mg/kg/infusion, i. v.) for 6 h daily sessions for 12 days. Each animal had a yoked saline control that received matched saline infusions. Animals were then tested on a progressive ratio schedule to measure motivation to obtain a single infusion of oxycodone. Drug seeking was measured following 28 days of forced abstinence using a 90-min cued/test. RTqPCR was utilized to measure mir182 and mRNA targets related to neuroplasticity (wnt3, plppr4, pou3f3, tle4, cacna2d, and bdnf) from the nucleus accumbens. Data revealed that animals responded on a continuum for oxycodone. When divided into two groups termed high- and low responders, animals diverged during self-administration acquisition and maintained differences in behavior and gene expression throughout the study. mir182 was upregulated in the nucleus accumbens of both high and low responders and negatively correlated with tle4, which showed a strong negative correlation with reinstatement behavior. mRNA target levels were correlated with behaviors associated with increased severity of OUD behavior in male rats.

Parkinson's disease gene, Synaptojanin1, dysregulates the surface maintenance of the dopamine transporter

Missense mutations of PARK20/SYNJ1 (synaptojanin1/Synj1) were found in complex forms of familial Parkinsonism. However, the Synj1-regulated molecular and cellular changes associated with dopaminergic dysfunction remain unknown. We now report a fast depletion of evoked dopamine and impaired maintenance of the axonal dopamine transporter (DAT) in the Synj1 haploinsufficient (Synj1+/-) neurons. While Synj1 has been traditionally known to facilitate the endocytosis of synaptic vesicles, we provide in vitro and in vivo evidence demonstrating that Synj1 haploinsufficiency results in an increase of total DAT but a reduction of the surface DAT. Synj1+/- neurons exhibit maladaptive DAT trafficking, which could contribute to the altered DA release. We showed that the loss of surface DAT is associated with the impaired 5'-phosphatase activity and the hyperactive PI(4,5)P2-PKCβ pathway downstream of Synj1 deficiency. Thus, our findings provided important mechanistic insight for Synj1-regulated DAT trafficking integral to dysfunctional DA signaling, which might be relevant to early Parkinsonism.

Fetal endocrine axes mRNA expression levels are related to sex and intrauterine position

BACKGROUND

The hypothalamic-pituitary-adrenal (HPA) and -gonadal (HPG) axes are two major pathways that connect the neural and endocrine systems in vertebrates. Factors such as prenatal stress and maternal exposure to exogenous steroids have been shown to affect these pathways during fetal development. Another less studied factor is the transfer of hormones across fetuses in multifetal pregnancies. This form of transfer has been shown to influence the morphology, anatomy, physiology, and behavior of the offspring in litter-bearing mammals, an influence termed the intrauterine position (IUP) effect. In this study, we sought to delineate how the IUP effects HPA and HPG brain receptors, peptides, and enzymes (hereafter components) in utero and how these influences may differ between males and females.

METHODS

We utilized the unconventional model of culled free-ranging nutria (Myocastor coypus), with its large natural variation. We collected brain tissues from nutria fetuses and quantified the expression of key HPA and HPG components in three brain regions: prefrontal cortex, hypothalamus, and striatum.

RESULTS

We found an interaction between sex and IUP in the mineralocorticoid receptor (MR), gonadotropin-releasing hormone receptor (GNRHR), androgen receptor (AR), and estrogen receptor alpha (ESR1). IUP was significant in both gonadotropin-releasing hormone (GnRH) and its receptor GNRHR, but in different ways. In the hypothalamus, fetuses adjacent to same-sex neighbors had higher expression of GnRH than fetuses neighboring the opposite sex. Conversely, in the cortex, GNRHR exhibited the inverse pattern, and fetuses that were neighboring the opposite sex had higher expression levels than those neighboring the same sex. Regardless of IUP, in most components that showed significant sex differences, female fetuses had higher mRNA expression levels than male fetuses. We also found that HPA and HPG components were highly related in the early stages of gestation, and that there was an interaction between sex and developmental stage. In the early stages of pregnancy, female component expression levels were more correlated than males', but in the last trimester of pregnancy, male components were more related to each other than female's.

CONCLUSIONS

This study suggests that there are sexually different mechanisms to regulate the HPA and HPG axes during fetal development. Higher mRNA expression levels of endocrine axes components may be a mechanism to help females cope with prolonged androgen exposure over a long gestational period. Additionally, these findings suggest different coordination requirements of male and female endocrine axes during stages of fetal development.

Sex differences in the distribution and density of regulatory interneurons in the striatum

Introduction

Dysfunction of the cortico-basal circuitry - including its primary input nucleus, the striatum - contributes to neuropsychiatric disorders, such as autism and Tourette Syndrome (TS). These conditions show marked sex differences, occurring more often in males than in females. Regulatory interneurons, such as cholinergic interneurons (CINs) and parvalbumin-expressing GABAergic fast spiking interneurons (FSIs), are implicated in human neuropsychiatric disorders such as TS, and ablation of these interneurons produces relevant behavioral pathology in male mice, but not in females. Here we investigate sex differences in the density and distribution of striatal interneurons.

Methods

We use stereological quantification of CINs, FSIs, and somatostatin-expressing (SOM) GABAergic interneurons in the dorsal striatum (caudate-putamen) and the ventral striatum (nucleus accumbens) in male and female mice.

Results

Males have a higher density of CINs than females, especially in the dorsal striatum; females have equal distribution between dorsal and ventral striatum. FSIs showed similar distributions, with a greater dorsal-ventral density gradient in males than in females. SOM interneurons were denser in the ventral than in the dorsal striatum, with no sex differences.

Discussion

These sex differences in the density and distribution of FSIs and CINs may contribute to sex differences in basal ganglia function, particularly in the context of psychopathology.

Androgen effects on mesoprefrontal dopamine systems in the adult male brain

Epidemiological data show that males are more often and/or more severely affected by symptoms of prefrontal cortical dysfunction in schizophrenia, Parkinson's disease and other disorders in which dopamine circuits associated with the prefrontal cortex are dysregulated. This review focuses on research showing that these dopamine circuits are powerfully regulated by androgens. It begins with a brief overview of the sex differences that distinguish prefrontal function in health and prefrontal dysfunction or decline in aging and/or neuropsychiatric disease. This review article then spotlights data from human subjects and animal models that specifically identify androgens as potent modulators of prefrontal cortical operations and of closely related, functionally critical measures of prefrontal dopamine level or tone. Candidate mechanisms by which androgens dynamically control mesoprefrontal dopamine systems and impact prefrontal states of hypo- and hyper-dopaminergia in aging and disease are then considered. This is followed by discussion of a working model that identifies a key locus for androgen modulation of mesoprefrontal dopamine systems as residing within the prefrontal cortex itself. The last sections of this review critically consider the ways in which the organization and regulation of mesoprefrontal dopamine circuits differ in the adult male and female brain, and highlights gaps where more research is needed.

Assessing the Relationship between Body Image Satisfaction and Physical Activity in Italian Adolescents: A Cross-Sectional Investigation

BACKGROUND

Body image perception can significantly influence various aspects of adolescent lives. The study analyzed the relationship between body image satisfaction and sports participation in adolescents, examining various factors that contribute to body image concerns and their implications for sports engagement.

METHODS

A total of 237 schoolchildren were recruited from lower secondary Italian schools. Anthropometric characteristics were measured directly. Assessment of body image perception was performed using Body Silhouette Charts for preadolescent children. The Italian version of the International Physical Activity Questionnaire for Adolescents questionnaire was administered to assess physical activity (PA) levels at school and during leisure time in the last 7 days. Analysis of variance was used to test differences in PA levels, while multiple regression models were carried out to assess possible predictors of body dissatisfaction.

RESULTS

In total, 42.6% of children were not satisfied with their figure and 23.2% were very dissatisfied; among them, the vast majority would have liked to be thinner. The dissatisfaction and satisfaction were similar in boys and girls. The frequency of satisfaction with one's body image was higher in children who practiced extracurricular sports compared to those who did not. The percentage of dissatisfaction with one's body image was similar in the two groups, but the frequency of children being very dissatisfied was double in the group that does not practice extracurricular sport (31.2% vs. 17.7%). Body dissatisfaction increases with increasing body mass index in both genders but decreases in children involved in extracurricular sports.

CONCLUSIONS

Encouraging teenagers to engage in regular physical activity should be a key component of therapies supporting positive body image. This study found a relationship between extracurricular sports and body image satisfaction, suggesting that physical activity protects teenagers' body image satisfaction.

Dopamine transmission at D1 and D2 receptors in the nucleus accumbens contributes to the expression of incubation of cocaine craving

Relapse represents a consistent clinical problem for individuals with substance use disorder. In the incubation of craving model of persistent craving and relapse, cue-induced drug seeking progressively intensifies or 'incubates' during the first weeks of abstinence from drug self-administration and then remains high for months. Previously, we and others have demonstrated that expression of incubated cocaine craving requires strengthening of excitatory synaptic transmission in the nucleus accumbens core (NAcc). However, despite the importance of dopaminergic signaling in the NAcc for motivated behavior, little is known about the role that dopamine (DA) plays in the incubation of cocaine craving. Here we used fiber photometry to measure DA transients in the NAcc of male and female rats during cue-induced seeking tests conducted in early abstinence from cocaine self-administration, prior to incubation, and late abstinence, after incubation of craving has plateaued. We observed DA transients time-locked to cue-induced responding but their magnitude did not differ significantly when measured during early versus late abstinence seeking tests. Next, we tested for a functional role of these DA transients by injecting DA receptor antagonists into the NAcc just before the cue-induced seeking test. Blockade of either D1 or D2 DA receptors reduced cue-induced cocaine seeking after but not before incubation. We found no main effect of sex in our experiments. These results suggest that DA contributes to incubated cocaine seeking but the emergence of this role reflects changes in postsynaptic responsiveness to DA rather than presynaptic alterations.

High-dose Agomelatine Combined with Haloperidol Decanoate Improves Cognition, Downregulates MT2, Upregulates D5, and Maintains Krüppel-like Factor 9 But Alters Cardiac Electrophysiology

Haloperidol decanoate (HD) has been implicated in cognitive impairment. Agomelatine (AGO) has been claimed to improve cognition. We aimed at investigating the effects of HD + low- or high-dose AGO on cognition, verifying the melatonergic/dopaminergic to the cholinergic hypothesis of cognition and exploring relevant cardiovascular issues in adult male Wistar albino rats. HD + high-dose AGO prolonged the step-through latency by +61.47% (P < 0.0001), increased the time spent in bright light by +439.49% (P < 0.0001), reduced the time spent in dim light by -66.25% (P < 0.0001), and increased the percent of alternations by +71.25% (P < 0.0001), despite the reductions in brain acetylcholine level by -10.67% (P < 0.0001). Neurodegeneration was minimal, while the mean power frequency of the source wave was reduced by -23.39% (P < 0.05). Concurrently, the relative expression of brain melatonin type 2 receptors was reduced by -18.75% (P < 0.05), against increased expressions of dopamine type 5 receptors by +22.22% (P < 0.0001) and angiopoietin-like 4 by +119.18% (P < 0.0001). Meanwhile, electrocardiogram (ECG) demonstrated inverted P wave, reduced P wave duration by -36.15% (P < 0.0001) and PR interval by -19.91% (P < 0.0001), prolonged RR interval by +27.97% (P < 0.05), increased R wave amplitude by +523.15% (P < 0.0001), and a depressed ST segment and inverted T wave. In rats administered AGO, HD, or HD+ low-dose AGO, Alzheimer's disease (AD)-like neuropathologic features were more evident, accompanied by extensive ECG and neurochemical alterations. HD + high-dose AGO enhances cognition but alters cardiac electrophysiology. SIGNIFICANCE STATEMENT: Given the issue of cognitive impairment associated with HD and the claimed cognitive-enhancing activity of AGO, combined high-dose AGO with HD improved cognition of adult male rats, who exhibited minimal neurodegenerative changes. HD+ high-dose AGO was relatively safe regarding triggering epileptogenesis, while it altered cardiac electrophysiology. In the presence of low acetylcholine, the melatonergic/dopaminergic hypothesis, added to angiopoietin-like 4 and Krüppel-like factor 9, could offer some clue, thus offering novel targets for pharmacologic manipulation of cognition.

A unique multi-synaptic mechanism involving acetylcholine and GABA regulates dopamine release in the nucleus accumbens through early adolescence in male rats

Adolescence is characterized by changes in reward-related behaviors, social behaviors, and decision-making. These behavioral changes are necessary for the transition into adulthood, but they also increase vulnerability to the development of a range of psychiatric disorders. Major reorganization of the dopamine system during adolescence is thought to underlie, in part, the associated behavioral changes and increased vulnerability. Here, we utilized fast scan cyclic voltammetry and microdialysis to examine differences in dopamine release as well as mechanisms that underlie differential dopamine signaling in the nucleus accumbens (NAc) core of adolescent (P28-35) and adult (P70-90) male rats. We show baseline differences between adult and adolescent-stimulated dopamine release in male rats, as well as opposite effects of the α6 nicotinic acetylcholine receptor (nAChR) on modulating dopamine release. The α6-selective blocker, α-conotoxin, increased dopamine release in early adolescent rats, but decreased dopamine release in rats beginning in middle adolescence and extending through adulthood. Strikingly, blockade of GABAA and GABAB receptors revealed that this α6-mediated increase in adolescent dopamine release requires NAc GABA signaling to occur. We confirm the role of α6 nAChRs and GABA in mediating this effect in vivo using microdialysis. Results herein suggest a multisynaptic mechanism potentially unique to the period of development that includes early adolescence, involving acetylcholine acting at α6-containing nAChRs to drive inhibitory GABA tone on dopamine release.

Sexual dimorphism in histamine regulation of striatal dopamine

Background

Many neuropsychiatric disorders show sex differences in prevalence and presentation. For example, Tourette's Syndrome (TS) is diagnosed 3-5 times more often in males. Dopamine modulation of the basal ganglia is implicated in numerous neuropsychiatric conditions, including TS. Motivated by an unexpected genetic finding in a family with TS, we previously characterized the modulation of striatal dopamine by histamine.

Methods

We used microdialysis to analyze striatal dopamine response to the targeted infusion of histamine and histamine agonists. siRNA knockdown of histamine receptors was used to identify the cellular mediators of observed effects.

Results

Intracerebroventricular histamine reduced striatal dopamine in male mice, replicating previous work. Unexpectedly, histamine increased striatal dopamine in females. Targeted infusion of selected agonists revealed that the effect in males depends on H2R receptors in the substantia nigra pars compacta (SNc). Knockdown of H2R in SNc GABAergic neurons abrogated the effect, identifying these cells as a key locus of histamine's regulation of dopamine in males. In females, in contrast, H2R had no role; instead, H3R agonists in the striatum increased striatal dopamine. Strikingly, the effect of histamine on dopamine in females was modulated by the estrous cycle, appearing in estrus/proestrus but not in metestrus/diestrus.

Conclusions

These findings confirm the regulation of striatal dopamine by histamine but identify marked sexual dimorphism in and estrous modulation of this effect. These findings may shed light on the mechanistic underpinnings of other sex differences in the striatal circuitry, perhaps including the marked sex differences seen in TS and related neuropsychiatric conditions.

A chromosome region linked to neurodevelopmental disorders acts in distinct neuronal circuits in males and females to control locomotor behavior

Biological sex shapes the manifestation and progression of neurodevelopmental disorders (NDDs). These disorders often demonstrate male-specific vulnerabilities; however, the identification of underlying mechanisms remains a significant challenge in the field. Hemideletion of the 16p11.2 region (16p11.2 del/+) is associated with NDDs, and mice modeling 16p11.2 del/+ exhibit sex-specific striatum-related phenotypes relevant to NDDs. Striatal circuits, crucial for locomotor control, consist of two distinct pathways: the direct and indirect pathways originating from D1 dopamine receptor (D1R) and D2 dopamine receptor (D2R) expressing spiny projection neurons (SPNs), respectively. In this study, we define the impact of 16p11.2 del/+ on striatal circuits in male and female mice. Using snRNA-seq, we identify sex- and cell type-specific transcriptomic changes in the D1- and D2-SPNs of 16p11.2 del/+ mice, indicating distinct transcriptomic signatures in D1-SPNs and D2-SPNs in males and females, with a ∼5-fold greater impact in males. Further pathway analysis reveals differential gene expression changes in 16p11.2 del/+ male mice linked to synaptic plasticity in D1- and D2-SPNs and GABA signaling pathway changes in D1-SPNs. Consistent with our snRNA-seq study revealing changes in GABA signaling pathways, we observe distinct changes in miniature inhibitory postsynaptic currents (mIPSCs) in D1- and D2-SPNs from 16p11.2 del/+ male mice. Behaviorally, we utilize conditional genetic approaches to introduce the hemideletion selectively in either D1- or D2-SPNs and find that conditional hemideletion of genes in the 16p11.2 region in D2-SPNs causes hyperactivity in male mice, but hemideletion in D1-SPNs does not. Within the striatum, hemideletion of genes in D2-SPNs in the dorsal lateral striatum leads to hyperactivity in males, demonstrating the importance of this striatal region. Interestingly, conditional 16p11.2 del/+ within the cortex drives hyperactivity in both sexes. Our work reveals that a locus linked to NDDs acts in different striatal circuits, selectively impacting behavior in a sex- and cell type-specific manner, providing new insight into male vulnerability for NDDs.

Highlights

- 16p11.2 hemideletion (16p11.2 del/+) induces sex- and cell type-specific transcriptomic signatures in spiny projection neurons (SPNs). - Transcriptomic changes in GABA signaling in D1-SPNs align with changes in inhibitory synapse function. - 16p11.2 del/+ in D2-SPNs causes hyperactivity in males but not females. - 16p11.2 del/+ in D2-SPNs in the dorsal lateral striatum drives hyperactivity in males. - 16p11.2 del/+ in cortex drives hyperactivity in both sexes.

Graphic abstract

Effects of age and sex on photoperiod modulation of nucleus accumbens monoamine content and release in adolescence and adulthood

Day length, or photoperiod, is a reliable environmental cue encoded by the brain's circadian clock that indicates changing seasons and induces seasonal biological processes. In humans, photoperiod, age, and sex have been linked to seasonality in neuropsychiatric disorders, as seen in Seasonal Affective Disorder, Major Depressive Disorder, and Bipolar Disorder. The nucleus accumbens is a key locus for the regulation of motivated behaviors and neuropsychiatric disorders. Using periadolescent and young adult male and female mice, here we assessed photoperiod's effect on serotonin and dopamine tissue content in the nucleus accumbens core, as well as on accumbal synaptic dopamine release and uptake. We found greater serotonin and dopamine tissue content in the nucleus accumbens from young adult mice raised in a Short winter-like photoperiod. In addition, dopamine release and clearance were greater in the nucleus accumbens from young adult mice raised in a Long summer-like photoperiod. Importantly, we found that photoperiod's effects on accumbal dopamine tissue content and release were sex-specific to young adult females. These findings support that in mice there are interactions across age, sex, and photoperiod that impact critical monoamine neuromodulators in the nucleus accumbens which may provide mechanistic insight into the age and sex dependencies in seasonality of neuropsychiatric disorders in humans.

Age and sex effects on paired-pulse suppression and prepulse inhibition of auditory evoked potentials

Responses to a sensory stimulus are inhibited by a preceding stimulus; if the two stimuli are identical, paired-pulse suppression (PPS) occurs; if the preceding stimulus is too weak to reliably elicit the target response, prepulse inhibition (PPI) occurs. PPS and PPI represent excitability changes in neural circuits induced by the first stimulus, but involve different mechanisms and are impaired in different diseases, e.g., impaired PPS in schizophrenia and Alzheimer's disease and impaired PPI in schizophrenia and movement disorders. Therefore, these measures provide information on several inhibitory mechanisms that may have roles in clinical conditions. In the present study, PPS and PPI of the auditory change-related cortical response were examined to establish normative data on healthy subjects (35 females and 32 males, aged 19-70 years). We also investigated the effects of age and sex on PPS and PPI to clarify whether these variables need to be considered as biases. The test response was elicited by an abrupt increase in sound pressure in a continuous sound and was recorded by electroencephalography. In the PPS experiment, the two change stimuli to elicit the cortical response were a 15-dB increase from the background of 65 dB separated by 600 ms. In the PPI experiment, the prepulse and test stimuli were 2- and 10-dB increases, respectively, with an interval of 50 ms. The results obtained showed that sex exerted similar effects on the two measures, with females having stronger test responses and weaker inhibition. On the other hand, age exerted different effects: aging correlated with stronger test responses and weaker inhibition in the PPS experiment, but had no effects in the PPI experiment. The present results suggest age and sex biases in addition to normative data on PPS and PPI of auditory change-related potentials. PPS and PPI, as well as other similar paradigms, such as P50 gating, may have different and common mechanisms. Collectively, they may provide insights into the pathophysiologies of diseases with impaired inhibitory function.

Sex differences in the distribution and density of regulatory interneurons in the striatum

Dysfunction of the cortico-basal circuitry - including its primary input nucleus, the striatum - contributes to neuropsychiatric disorders, including autism and Tourette Syndrome (TS). These conditions show marked sex differences, occurring more often in males than in females. Regulatory interneurons, including cholinergic interneurons (CINs) and parvalbumin-expressing GABAergic fast spiking interneurons (FSIs), are implicated in human neuropsychiatric disorders such as TS, and ablation of these interneurons produces relevant behavioral pathology in male mice, but not in females. Here we investigate sex differences in the density and distribution of striatal interneurons, using stereological quantification of CINs, FSIs, and somatostatin-expressing (SOM) GABAergic interneurons in the dorsal striatum (caudate-putamen) and the ventral striatum (nucleus accumbens) in male and female mice. Males have a higher density of CINs than females, especially in the dorsal striatum; females have equal distribution between dorsal and ventral striatum. FSIs showed similar effects, with a greater dorsal-ventral density gradient in males than in females. SOM interneurons were denser in the ventral than in the dorsal striatum, with no sex differences. These sex differences in the density and distribution of FSIs and CINs may contribute to sex differences in basal ganglia function, including in the context of psychopathology.

GABA co-released from striatal dopamine axons dampens phasic dopamine release through autoregulatory GABAA receptors

Striatal dopamine axons co-release dopamine and gamma-aminobutyric acid (GABA), using GABA provided by uptake via GABA transporter-1 (GAT1). Functions of GABA co-release are poorly understood. We asked whether co-released GABA autoinhibits dopamine release via axonal GABA type A receptors (GABAARs), complementing established inhibition by dopamine acting at axonal D2 autoreceptors. We show that dopamine axons express α3-GABAAR subunits in mouse striatum. Enhanced dopamine release evoked by single-pulse optical stimulation in striatal slices with GABAAR antagonism confirms that an endogenous GABA tone limits dopamine release. Strikingly, an additional inhibitory component is seen when multiple pulses are used to mimic phasic axonal activity, revealing the role of GABAAR-mediated autoinhibition of dopamine release. This autoregulation is lost in conditional GAT1-knockout mice lacking GABA co-release. Given the faster kinetics of ionotropic GABAARs than G-protein-coupled D2 autoreceptors, our data reveal a mechanism whereby co-released GABA acts as a first responder to dampen phasic-to-tonic dopamine signaling.

Young human alpha synuclein transgenic (BAC-SNCA) mice display sex- and gene-dose-dependent phenotypic disturbances

Parkinson's disease (PD) is a common neurodegenerative movement disorder, characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta and the accumulation of aggregated alpha synuclein (aSyn). The disease often presents with early prodromal non-motor symptoms and later motor symptoms. Diagnosing PD based purely on motor symptoms is often too late for successful intervention, as a significant neuronal loss has already occurred. Furthermore, the lower prevalence of PD in females is not well understood, highlighting the need for a better understanding of the interaction between sex and aSyn, the crucial protein for PD pathogenesis. Here, we conducted a comprehensive phenotyping study in 1- to 5-month-old mice overexpressing human aSyn gene (SNCA) in a bacterial artificial chromosome (BAC-SNCA). We demonstrate a SNCA gene-dose-dependent increase of human aSyn and phosphorylated aSyn, as well as a decrease in tyrosine hydroxylase expression in BAC-SNCA mice, with more pronounced effects in male mice. Phosphorylated aSyn was already found in the dorsal motor nucleus of the vagus nerve of 2-month-old mice. This was time-wise associated with significant gait altrations in BAC-SNCA mice as early as 1 and 3 months of age using CatWalk gait analysis. Furthermore, anxiety-related behavioral tests revealed an increase in anxiety levels in male BAC-SNCA mice. Finally, 5-month-old male BAC-SNCA mice exhibited a SNCA gene-dose-dependent elevation in energy expenditure in automated home-cage monitoring. For the first time, these findings describe early-onset, sex- and gene-dose-dependent, aSyn-mediated disturbances in BAC-SNCA mice, providing a model for sex-differences, early-onset neuropathology, and prodromal symptoms of PD.

Sex difference in the effect of environmental enrichment on food restriction-induced persistence of cocaine conditioned place preference and mechanistic underpinnings

Psychosocial and environmental factors, including loss of natural reward, contribute to the risk of drug abuse. Reward loss has been modeled in animals by removal from social or sexual contact, transfer from enriched to impoverished housing, or restriction of food. We previously showed that food restriction increases the unconditioned rewarding effects of abused drugs and the conditioned incentive effects of drug-paired environments. Mechanistic studies provided evidence of decreased basal dopamine (DA) transmission, adaptive upregulation of signaling downstream of D1 DA receptor stimulation, synaptic upscaling and incorporation of calcium-permeable AMPA receptors (CP-AMPARs) in medium spiny neurons (MSNs) of nucleus accumbens (NAc). These findings align with the still evolving 'reward deficiency' hypothesis of drug abuse. The present study tested whether a compound natural reward that is known to increase DA utilization, environmental enrichment, would prevent the persistent expression of cocaine conditioned place preference (CPP) otherwise observed in food restricted rats, along with the mechanistic underpinnings. Because nearly all prior investigations of both food restriction and environmental enrichment effects on cocaine CPP were conducted in male rodents, both sexes were included in the present study. Results indicate that environmental enrichment curtailed the persistence of CPP expression, decreased signaling downstream of the D1R, and decreased the amplitude and frequency of spontaneous excitatory postsynaptic currents (EPSCs) in NAc MSNs of food restricted male, but not female, rats. The failure of environmental enrichment to significantly decrease food restriction-induced synaptic insertion of CP-AMPARs, and how this may accord with previous pharmacological findings that blockade of CP-AMPARs reverses behavioral effects of food restriction is discussed. In addition, it is speculated that estrous cycle-dependent fluctuations in DA release, receptor density and MSN excitability may obscure the effect of increased DA signaling during environmental enrichment, thereby interfering with development of the cellular and behavioral effects that enrichment produced in males.

Influence of Inherited Seizure Susceptibility on Intermittent Voluntary Alcohol Consumption and Alcohol Withdrawal Seizures in Genetically Epilepsy-Prone Rats (GEPR-3s)

BACKGROUND

The link between epilepsy and alcohol consumption is complex, with conflicting reports. To enhance our understanding of this link, we conducted a study to determine how inherited seizure susceptibility affects voluntary alcohol consumption and influences alcohol withdrawal seizures in male and female genetically epilepsy-prone rats (GEPR-3s) compared to Sprague Dawley (SD) rats.

METHODS

In the first experiment, animals were given access to two bottles simultaneously, one containing water and the other 7.5%, 15%, or 30% (v/v) alcohol three times a week for each dose after acclimation to drinking water. In a second experiment, animals were tested for acoustically evoked alcohol seizures 24 h after the last session of voluntary alcohol consumption.

RESULTS

Analysis revealed that GEPR-3s (males and females) had lower alcohol intake and preference than SD rats, particularly at lower alcohol concentrations. However, female GEPR-3s consumed more alcohol and had a higher alcohol preference than males. Furthermore, withdrawal from voluntary alcohol consumption facilitated the onset and duration of seizures in GEPR-3s.

CONCLUSIONS

Our study suggests that genetic seizure susceptibility in GEPR-3s is negatively associated with alcohol consumption. However, withdrawal from low to moderate amounts of alcohol intake can promote epileptogenesis in the epileptic GEPR-3s.

Decoupling Dopamine Synthesis from Impulsive Action, Risk-Related Decision-Making, and Propensity to Cocaine Intake: A Longitudinal [18F]-FDOPA PET Study in Roman High- and Low-Avoidance Rats

Impulsive action and risk-related decision-making (RDM) are two facets of impulsivity linked to a hyperdopaminergic release in the striatum and an increased propensity to cocaine intake. We previously showed that with repeated cocaine exposure, this initial hyperdopaminergic release is blunted in impulsive animals, potentially signaling drug-induced tolerance. Whether such dopaminergic dynamics involve changes in dopamine (DA) synthesis as a function of impulsivity is currently unknown. Here, we investigated the predictive value of DA synthesis for impulsive action, RDM, and the propensity to take cocaine in a rat model of vulnerability to cocaine abuse. Additionally, we assessed the effects of cocaine intake on these variables. Rats were tested sequentially in the rat Gambling Task (rGT) and were scanned with positron emission tomography and [18F]-FDOPA to respectively assess both impulsivity facets and striatal DA synthesis before and after cocaine self-administration (SA). Our results revealed that baseline striatal levels of DA synthesis did not significantly predict impulsive action, RDM, or a greater propensity to cocaine SA in impulsive animals. Besides, we showed that impulsive action, but not RDM, predicted higher rates of cocaine taking. However, chronic cocaine exposure had no impact on DA synthesis, nor affected impulsive action and RDM. These findings indicate that the hyper-responsive DA system associated with impulsivity and a propensity for cocaine consumption, along with the reduction in this hyper-responsive DA state in impulsive animals with a history of cocaine use, might not be mediated by dynamic changes in DA synthesis.

A mouse model of the 3-hit effects of stress: Genotype controls the effects of life adversities in females

Helplessness is a dysfunctional coping response to stressors associated with different psychiatric conditions. The present study tested the hypothesis that early and adult adversities cumulate to produce helplessness depending on the genotype (3-hit hypothesis of psychopathology). To this aim, we evaluated whether Chronic Unpredictable Stress (CUS) differently affected coping and mesoaccumbens dopamine (DA) responses to stress challenge by adult mice of the C57BL/6J (B6) and DBA/2J (D2) inbred strains depending on early life experience (Repeated Cross Fostering, RCF). Three weeks of CUS increased the helplessness expressed in the Forced Swimming Test (FST) and the Tail Suspension Test by RCF-exposed female mice of the D2 strain. Moreover, female D2 mice with both RCF and CUS experiences showed inhibition of the stress-induced extracellular DA outflow in the Nucleus Accumbens, as measured by in vivo microdialysis, during and after FST. RCF-exposed B6 mice, instead, showed reduced helplessness and increased mesoaccumbens DA release. The present results support genotype-dependent additive effects of early experiences and adult adversities on behavioral and neural responses to stress by female mice. To our knowledge, this is the first report of a 3-hit effect in an animal model. Finally, the comparative analyses of behavioral and neural phenotypes expressed by B6 and D2 mice suggest some translationally relevant hypotheses of genetic risk factors for psychiatric disorders.

Dopamine D2 receptors in hilar mossy cells regulate excitatory transmission and hippocampal function

Hilar mossy cells (MCs) are principal excitatory neurons of the dentate gyrus (DG) that play critical roles in hippocampal function and have been implicated in brain disorders such as anxiety and epilepsy. However, the mechanisms by which MCs contribute to DG function and disease are poorly understood. A defining feature of MCs is the promoter activity of the dopamine D2 receptor (D2R) gene (Drd2), and previous work indicates a key role for dopaminergic signaling in the DG. Additionally, the involvement of D2R signaling in cognition and neuropsychiatric conditions is well known. Surprisingly, though, the function of MC D2Rs remains largely unexplored. In this study, we show that selective and conditional removal of Drd2 from MCs of adult mice impaired spatial memory, promoted anxiety-like behavior, and was proconvulsant. To determine the subcellular expression of D2Rs in MCs, we used a D2R knockin mouse which revealed that D2Rs are enriched in the inner molecular layer of the DG, where MCs establish synaptic contacts with granule cells (GCs). D2R activation by exogenous and endogenous dopamine reduced MC to dentate GC synaptic transmission, most likely by a presynaptic mechanism. In contrast, exogenous dopamine had no significant impact on MC excitatory inputs and passive and active properties. Our findings support that MC D2Rs are essential for proper DG function by reducing MC excitatory drive onto GCs. Lastly, impairment of MC D2R signaling could promote anxiety and epilepsy, therefore highlighting a potential therapeutic target.

CHL1 depletion affects dopamine receptor D2-dependent modulation of mouse behavior

Introduction

The dopaminergic system plays a key role in the appropriate functioning of the central nervous system, where it is essential for emotional balance, arousal, reward, and motor control. The cell adhesion molecule close homolog of L1 (CHL1) contributes to dopaminergic system development, and CHL1 and the dopamine receptor D2 (D2R) are associated with mental disorders like schizophrenia, addiction, autism spectrum disorder and depression.

Methods

Here, we investigated how the interplay between CHL1 and D2R affects the behavior of young adult male and female wild-type (CHL+/+) and CHL1-deficient (CHL1-/-) mice, when D2R agonist quinpirole and antagonist sulpiride are applied.

Results

Low doses of quinpirole (0.02 mg/kg body weight) induced hypolocomotion of CHL1+/+ and CHL1-/- males and females, but led to a delayed response in CHL1-/- mice. Sulpiride (1 mg/kg body weight) affected locomotion of CHL1-/- females and social interaction of CHL1+/+ females as well as social interactions of CHL1-/- and CHL1+/+ males. Quinpirole increased novelty-seeking behavior of CHL1-/- males compared to CHL1+/+ males. Vehicle-treated CHL1-/- males and females showed enhanced working memory and reduced stress-related behavior.

Discussion

We propose that CHL1 regulates D2R-dependent functions in vivo. Deficiency of CHL1 leads to abnormal locomotor activity and emotionality, and to sex-dependent behavioral differences.

Gestational ethanol exposure impairs motor skills in female mice through dysregulated striatal dopamine and acetylcholine function

Fetal alcohol exposure has deleterious consequences on the motor skills of patients affected by Fetal Alcohol Spectrum Disorder (FASD) and in pre-clinical models of gestational ethanol exposure (GEE). Deficits in striatal cholinergic interneurons (CINs) and dopamine function impair action learning and execution, yet the effects of GEE on acetylcholine (ACh) and striatal dopamine release remain unexplored. Here, we report that alcohol exposure during the first ten postnatal days (GEEP0-P10), which mimics ethanol consumption during the last gestational trimester in humans, induces sex-specific anatomical and motor skill deficits in female mice during adulthood. Consistent with these behavioral impairments, we observed increased stimulus evoked-dopamine levels in the dorsolateral striatum (DLS) of GEEP0-P10 female, but not male, mice. Further experiments revealed sex-specific deficits in β2-containing nicotinic ACh receptor (nAChR)-modulation of electrically evoked dopamine release. Moreover, we found a reduced decay of ACh transients and a decreased excitability of striatal CINs in DLS of GEEP0-P10 females, indicating striatal CIN dysfunctions. Finally, the administration of varenicline, a β2-containing nAChR partial agonist, and chemogenetic-mediated increase in CIN activity improved motor performance in adult GEEP0-P10 females. Altogether, these data shed new light on GEE-induced striatal deficits and establish potential pharmacological and circuit-specific interventions to ameliorate motor symptoms of FASD.

Sex-dependent impact of perinatal 5G electromagnetic field exposure in the adolescent rat behavior

The fifth generation (5G) network is currently being worldwide spread out, raising questions about the potential impact of this new technology, particularly on immature organisms. The current study aimed to investigate the effects of daily 5G electromagnetic field (EMF) perinatal exposure on the neurodevelopment of rats. The exposure level was set to the limit of whole-body public exposure defined by the International Commission on Non-Ionizing Radiation Protection. The mother rat specific absorption rate (SAR) was 0.07 W/kg for 22 h/day at 3500 MHz continuous wave from gestational day (GD) 8 to post-natal day (PND) 21. Clinical observations were performed on weight, length, sex ratio, number of pups per litter, and number of stillborn in sham and EMF-exposed groups (n = 7). The age of pinna ear detachment, incisor eruption, and eye opening were recorded. Behavior was assessed on righting, gripping, and negative geotaxis reflexes at PND 3 or 7 and on stereotyped and horizontal movements in the open field at PND 43. Our results indicated that both male and female pups showed delayed incisor eruption in the EMF-exposed group compared to the sham group (+ 1 day). Regarding activity in the open field, adolescent females showed less stereotyped movements (- 70%), while adolescent males showed more stereotyped movements (+ 50%) compared to the sham-exposed adolescent rats. Thus, the present study suggested that perinatal exposure to 5G at SAR level below reglementary threshold led to perturbations in the descendants seen in juveniles and adolescents.

An automatic analysis framework for FDOPA PET neuroimaging

In this study we evaluate the performance of a fully automated analytical framework for FDOPA PET neuroimaging data, and its sensitivity to demographic and experimental variables and processing parameters. An instance of XNAT imaging platform was used to store the King's College London institutional brain FDOPA PET imaging archive, alongside individual demographics and clinical information. By re-engineering the historical Matlab-based scripts for FDOPA PET analysis, a fully automated analysis pipeline for imaging processing and data quantification was implemented in Python and integrated in XNAT. The final data repository includes 892 FDOPA PET scans organized from 23 different studies. We found good reproducibility of the data analysis by the automated pipeline (in the striatum for the Kicer: for the controls ICC = 0.71, for the psychotic patients ICC = 0.88). From the demographic and experimental variables assessed, gender was found to most influence striatal dopamine synthesis capacity (F = 10.7, p < 0.001), with women showing greater dopamine synthesis capacity than men. Our automated analysis pipeline represents a valid resourse for standardised and robust quantification of dopamine synthesis capacity using FDOPA PET data. Combining information from different neuroimaging studies has allowed us to test it comprehensively and to validate its replicability and reproducibility performances on a large sample size.

Dorsal BNST DRD2+ neurons mediate sex-specific anxiety-like behavior induced by chronic social isolation

The dorsal bed nucleus of stria terminalis (dBNST) is a pivotal hub for stress response modulation. Dysfunction of dopamine (DA) network is associated with chronic stress, but the roles of DA network of dBNST in chronic stress-induced emotional disorders remain unclear. We examine the role of dBNST Drd1⁺ and Drd2⁺ neurons in post-weaning social isolation (PWSI)-induced behavior deficits. We find that male, but not female, PWSI rats exhibit negative emotional phenotypes and the increase of excitability and E-I balance of dBNST Drd2⁺ neurons. More importantly, hypofunction of dBNST Drd2 receptor underlies PWSI-stress-induced male-specific neuronal plasticity change of dBNST Drd2⁺ neurons. Furthermore, chemogenetic activation of dBNST Drd2⁺ neurons is sufficient to induce anxiogenic effects, while Kir4.1-mediated chronic inhibition of dBNST Drd2⁺ neurons ameliorate PWSI-induced anxiety-like behaviors. Our findings reveal an important neural mechanism underlying PWSI-induced sex-specific behavioral abnormalities and potentially provide a target for the treatment of social stress-related emotional disorder.

The transcriptional response to acute cocaine is inverted in male mice with a history of cocaine self-administration and withdrawal throughout the mesocorticolimbic system

A large body of work has demonstrated that cocaine-induced changes in transcriptional regulation play a central role in the onset and maintenance of cocaine use disorder. An underappreciated aspect of this area of research, however, is that the pharmacodynamic properties of cocaine can change depending on an organism's previous drug-exposure history. In this study, we utilized RNA sequencing to characterize how the transcriptome-wide effects of acute cocaine exposure were altered by a history of cocaine self-administration and long-term withdrawal (30 days) in the ventral tegmental area (VTA), nucleus accumbens (NAc), and prefrontal cortex (PFC) in male mice. First, we found that the gene expression patterns induced by a single cocaine injection (10 mg/kg) were discordant between cocaine-naïve mice and mice in withdrawal from cocaine self-administration. Specifically, the same genes that were upregulated by acute cocaine in cocaine-naïve mice were downregulated by the same dose of cocaine in mice undergoing long-term withdrawal; the same pattern of opposite regulation was observed for the genes downregulated by initial acute cocaine exposure. When we analyzed this dataset further, we found that the gene expression patterns that were induced by long-term withdrawal from cocaine self-administration showed a high degree of overlap with the gene expression patterns of acute cocaine exposure - even though animals had not consumed cocaine in 30 days. Interestingly, cocaine re-exposure at this withdrawal time point reversed this expression pattern. Finally, we found that this pattern was similar across the VTA, PFC, NAc, and within each brain region the same genes were induced by acute cocaine, re-induced during long-term withdrawal, and reversed by cocaine re-exposure. Together, we identified a longitudinal pattern of gene regulation that is conserved across the VTA, PFC, and NAc, and characterized the genes constituting this pattern in each brain region.

Sex differences in VTA GABA transmission and plasticity during opioid withdrawal

The effectiveness of current treatments for opioid use disorder (OUD) varies by sex. Our understanding of the neurobiological mechanisms mediating negative states during withdrawal is lacking, particularly with regard to sex differences. Based on preclinical research in male subjects, opioid withdrawal is accompanied by increased gamma-aminobutyric acid (GABA) release probability at synapses onto dopamine neurons in the ventral tegmental area (VTA). It is unclear, however, if the physiological consequences of morphine that were originally elucidated in male rodents extend to females. The effects of morphine on the induction of future synaptic plasticity are also unknown. Here, we show that inhibitory synaptic long-term potentiation (LTP_GABA) is occluded in the VTA in male mice after repeated morphine injections and 1 day of withdrawal, while morphine-treated female mice maintain the ability to evoke LTP_GABA and have basal GABA activity similar to controls. Our observation of this physiological difference between male and female mice connects previous reports of sex differences in areas upstream and downstream of the GABA-dopamine synapse in the VTA during opioid withdrawal. The sex differences highlight the mechanistic distinctions between males and females that can be targeted when designing and implementing treatments for OUD.

Movement disorders associated with substance use in adults living in precarious housing or homelessness

OBJECTIVE

Many individuals living in precarious housing or homelessness have multimorbid illnesses, including substance use, psychiatric, and neurological disorders. Movement disorders (MDs) associated substance use are amongst the poorly studied subtopics of drug-induced MDs. The aim of the present study was, therefore, to determine the proportion affected and severity of different signs of MDs, as well as their associations with substance use in a community-based sample of precariously housed and homeless individuals.

METHODS

Participants were recruited from an impoverished urban neighborhood and were assessed for substance dependence and self-reported substance use (alcohol, cannabis, cocaine, methamphetamine, nicotine, and opioids), as well as for the severity of signs of MDs (akathisia, dyskinesia, dystonia, and parkinsonism). Adjusted regression models were used to estimate the associations of the severity of signs with the frequency of substance use over the past 4 weeks and with the baseline diagnosis of substance dependence.

RESULTS

The proportion of the sample with clinically relevant signs of MDs in any of the four categories was 18.6% (n = 401), and these participants demonstrated lower levels of functioning than those without signs. Of the different types of substance use, only methamphetamine (its frequency of use and dependence) was significantly associated with greater severity of overall signs of MDs. Frequency of methamphetamine use significantly interacted with age and sex, whereby older female participants exhibited the greatest overall severity with increased methamphetamine use. Of the different signs of MDs, methamphetamine use frequency was positively associated with the severity of trunk/limb dyskinesia and hypokinetic parkinsonism. Relative to no use, concurrent use of antipsychotics demonstrated lower severity of trunk/limb dyskinesia and greater severity of hypokinetic parkinsonism with methamphetamine use, and greater severity of dystonia with cocaine use.

CONCLUSIONS

Our study found a high proportion of MDs in a relatively young sample, and their severity was consistently associated with methamphetamine use, moderated by participant demographics and antipsychotic use. These disabling sequelae represent an important and understudied neurological condition that may affect quality of life and will require further study.

Dopamine D2 receptors in mossy cells reduce excitatory transmission and are essential for hippocampal function

Hilar mossy cells (MCs) are principal excitatory neurons of the dentate gyrus (DG) that play critical roles in hippocampal function and have been implicated in brain disorders such as anxiety and epilepsy. However, the mechanisms by which MCs contribute to DG function and disease are poorly understood. Expression from the dopamine D2 receptor (D2R) gene (Drd2) promoter is a defining feature of MCs, and previous work indicates a key role for dopaminergic signaling in the DG. Additionally, the involvement of D2R signaling in cognition and neuropsychiatric conditions is well-known. Surprisingly, though, the function of MC D2Rs remain largely unexplored. In this study, we show that selective and conditional removal of Drd2 from MCs of adult mice impaired spatial memory, promoted anxiety-like behavior and was proconvulsant. To determine the subcellular expression of D2Rs in MCs, we used a D2R knockin mouse which revealed that D2Rs are enriched in the inner molecular layer of the DG, where MCs establish synaptic contacts with granule cells. D2R activation by exogenous and endogenous dopamine reduced MC to dentate granule cells (GC) synaptic transmission, most likely by a presynaptic mechanism. In contrast, removing Drd2 from MCs had no significant impact on MC excitatory inputs and passive and active properties. Our findings support that MC D2Rs are essential for proper DG function by reducing MC excitatory drive onto GCs. Lastly, impairment of MC D2R signaling could promote anxiety and epilepsy, therefore highlighting a potential therapeutic target.

Mouse spontaneous behavior reflects individual variation rather than estrous state

Behavior is shaped by both the internal state of an animal and its individual behavioral biases. Rhythmic variation in gonadal hormones during the estrous cycle is a defining feature of the female internal state, one that regulates many aspects of sociosexual behavior. However, it remains unclear whether estrous state influences spontaneous behavior and, if so, how these effects might relate to individual behavioral variation. Here, we address this question by longitudinally characterizing the open-field behavior of female mice across different phases of the estrous cycle, using unsupervised machine learning to decompose spontaneous behavior into its constituent elements.1,2,3,4 We find that each female mouse exhibits a characteristic pattern of exploration that uniquely identifies it as an individual across many experimental sessions; by contrast, estrous state only negligibly impacts behavior, despite its known effects on neural circuits that regulate action selection and movement. Like female mice, male mice exhibit individual-specific patterns of behavior in the open field; however, the exploratory behavior of males is significantly more variable than that expressed by females both within and across individuals. These findings suggest underlying functional stability to the circuits that support exploration in female mice, reveal a surprising degree of specificity in individual behavior, and provide empirical support for the inclusion of both sexes in experiments querying spontaneous behaviors.

Insights into the mechanisms underlying opioid use disorder and potential treatment strategies

Opioid use disorder is a worldwide societal problem and public health burden. Strategies for treating opioid use disorder can be divided into those that target the opioid receptor system and those that target non-opioid receptor systems, including the dopamine and glutamate receptor systems. Currently, the clinical drugs used to treat opioid use disorder include the opioid receptor agonists methadone and buprenorphine, which are limited by their abuse liability, and the opioid receptor antagonist naltrexone, which is limited by poor compliance. Therefore, the development of effective medications with lower abuse liability and better potential for compliance is urgently needed. Based on recent advances in the understanding of the neurobiological mechanisms underlying opioid use disorder, potential treatment strategies and targets have emerged. This review focuses on the progress made in identifying potential targets and developing medications to treat opioid use disorder, including progress made by our laboratory, and provides insights for future medication development. LINKED ARTICLES: This article is part of a themed issue on Advances in Opioid Pharmacology at the Time of the Opioid Epidemic. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.7/issuetoc.

Active vs passive novelty-related strategies: Sex differences in exploratory behaviour and monoaminergic systems

Sex differences are apparent in numerous behavioural characteristics. In order to compare and characterise male and female variability of exploratory behaviour, 365 male and 401 female rats were assessed in a task where a bimodal response distribution had previously been established in males. Female rats had significantly higher exploratory activity, and presented normal distribution of the behaviour, very differently from the bimodal distribution of males. No major effect of litter or oestrous cycle was detected. Several differences between male and female rats were found in monoamine metabolism measured ex vivo. Male rats had lower levels of dopamine (DA) in frontal cortex, and higher levels of 3,4-dihydroxyphenylacetic acid (DOPAC) in raphe area; higher levels of serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in dorsal striatum but lower levels of 5-HT and 5-HIAA in locus coeruleus area, 5-HIAA levels were also lower in hippocampus as compared to females. Males had higher noradrenaline (NA) levels in hippocampus and lower normetanephrine (NMN) levels in striatum, in both brain regions male animals had lower NMN/NA ratio. No sex difference was found in accumbens. The only brain region with an interaction between sex and the expression of exploratory activity was raphe: Here 5-HT levels were lower, and DOPAC levels and DOPAC/DA and 5-HIAA/5-HT ratios higher in low exploring male but not female rats. Conclusively, female rats not only display higher levels of exploration but the population distribution of this behaviour is distinct; this may be related to differences in the monoaminergic systems between female and male animals.

Elevated prefrontal dopamine interferes with the stress-buffering properties of behavioral control in female rats

Stress-linked disorders are more prevalent in women than in men and differ in their clinical presentation. Thus, investigating sex differences in factors that promote susceptibility or resilience to stress outcomes, and the circuit elements that mediate their effects, is important. In male rats, instrumental control over stressors engages a corticostriatal system involving the prelimbic cortex (PL) and dorsomedial striatum (DMS) that prevent many of the sequelae of stress exposure. Interestingly, control does not buffer against stress outcomes in females, and here, we provide evidence that the instrumental controlling response in females is supported instead by the dorsolateral striatum (DLS). Additionally, we used in vivo microdialysis, fluorescent in situ hybridization, and receptor subtype pharmacology to examine the contribution of prefrontal dopamine (DA) to the differential impact of behavioral control. Although both sexes preferentially expressed D1 receptor mRNA in PL GABAergic neurons, there were robust sex differences in the dynamic properties of prefrontal DA during controllable stress. Behavioral control potently attenuated stress-induced DA efflux in males, but not females, who showed a sustained DA increase throughout the entire stress session. Importantly, PL D1 receptor blockade (SCH 23390) shifted the proportion of striatal activity from the DLS to the DMS in females and produced the protective effects of behavioral control. These findings suggest a sex-selective mechanism in which elevated DA in the PL biases instrumental responding towards prefrontal-independent striatal circuitry, thereby eliminating the protective impact of coping with stress.

Associations of white blood cell and platelet counts with specific depressive symptom dimensions in patients with bipolar disorder: Analysis of data from the FACE-BD cohort

Evidences suggest that inflammation is increased in a subgroup of patients with depression. Moreover, increased peripheral inflammatory markers (cells and proteins) are associated with some, but not all depressive symptoms. On the other hand, similar studies on bipolar disorders mainly focused on blood cytokines. Here, we analysed data from a large (N = 3440), well-characterized cohort of individuals with bipolar disorder using Kendall partial rank correlation, multivariate linear regression, and network analyses to determine whether peripheral blood cell counts are associated with depression severity, its symptoms, and dimensions. Based on the self-reported 16-Item Quick Inventory of Depressive Symptomatology questionnaire scores, we preselected symptom dimensions based on literature and data-driven principal component analysis. We found that the counts of all blood cell types were only marginally associated with depression severity. Conversely, white blood cell count was significantly associated with the sickness dimension and its four components (anhedonia, slowing down, fatigue, and appetite loss). Platelet count was associated with the insomnia/restlessness dimension and its components (initial, middle, late insomnia and restlessness). Principal component analyses corroborated these results. Platelet count was also associated with suicidal ideation. In analyses stratified by sex, the white blood cell count-sickness dimension association remained significant only in men, and the platelet count-insomnia/restlessness dimension association only in women. Without implying causation, these results suggest that peripheral blood cell counts might be associated with different depressive symptoms in individuals with bipolar disorder, and that white blood cells might be implicated in sickness symptoms and platelets in insomnia/agitation and suicidal ideation.

Photoperiod Impacts Nucleus Accumbens Dopamine Dynamics

Circadian photoperiod, or day length, changes with the seasons and influences behavior to allow animals to adapt to their environment. Photoperiod is also associated with seasonal rhythms of affective state, as evidenced by seasonality of several neuropsychiatric disorders. Interestingly, seasonality tends to be more prevalent in women for affective disorders such as major depressive disorder and bipolar disorder (BD). However, the underlying neurobiological processes contributing to sex-linked seasonality of affective behaviors are largely unknown. Mesolimbic dopamine input to the nucleus accumbens (NAc) contributes to the regulation of affective state and behaviors. Additionally, sex differences in the mesolimbic dopamine pathway are well established. Therefore, we hypothesize that photoperiod may drive differential modulation of NAc dopamine in males and females. Here, we used fast-scan cyclic voltammetry (FSCV) to explore whether photoperiod can modulate subsecond dopamine signaling dynamics in the NAc core of male and female mice raised in seasonally relevant photoperiods. We found that photoperiod modulates dopamine signaling in the NAc core, and that this effect is sex-specific to females. Both release and uptake of dopamine were enhanced in the NAc core of female mice raised in long, summer-like photoperiods, whereas we did not find photoperiodic effects on NAc core dopamine in males. These findings uncover a potential neural circuit basis for sex-linked seasonality in affective behaviors.

17β-estradiol does not have a direct effect on the function of striatal cholinergic interneurons in adult mice in vitro

The striatum is an essential component of the basal ganglia that is involved in motor control, action selection and motor learning. The pathophysiological changes of the striatum are present in several neurological and psychiatric disorder including Parkinson's and Huntington's diseases. The striatal cholinergic neurons are the main regulators of striatal microcircuitry. It has been demonstrated that estrogen exerts various effects on neuronal functions in dopaminergic and medium spiny neurons (MSN), however little is known about how the activity of cholinergic interneurons are influenced by estrogens. In this study we examined the acute effect of 17β-estradiol on the function of striatal cholinergic neurons in adult mice in vitro. We also tested the effect of estrus cycle and sex on the spontaneous activity of cholinergic interneurons in the striatum. Our RNAscope experiments showed that ERα, ERβ, and GPER1 receptor mRNAs are expressed in some striatal cholinergic neurons at a very low level. In cell-attached patch clamp experiments, we found that a high dose of 17β-estradiol (100 nM) affected the spontaneous firing rate of these neurons only in old males. Our findings did not demonstrate any acute effect of a low concentration of 17β-estradiol (100 pM) or show any association of estrus cycle or sex with the activity of striatal cholinergic neurons. Although estrogen did not induce changes in the intrinsic properties of neurons, indirect effects via modulation of the synaptic inputs of striatal cholinergic interneurons cannot be excluded.

Sex differences in chronic pain-induced mental disorders: Mechanisms of cerebral circuitry

Mental disorders such as anxiety and depression induced by chronic pain are common in clinical practice, and there are significant sex differences in their epidemiology. However, the circuit mechanism of this difference has not been fully studied, as preclinical studies have traditionally excluded female rodents. Recently, this oversight has begun to be resolved and studies including male and female rodents are revealing sex differences in the neurobiological processes behind mental disorder features. This paper reviews the structural functions involved in the injury perception circuit and advanced emotional cortex circuit. In addition, we also summarize the latest breakthroughs and insights into sex differences in neuromodulation through endogenous dopamine, 5-hydroxytryptamine, GABAergic inhibition, norepinephrine, and peptide pathways like oxytocin, as well as their receptors. By comparing sex differences, we hope to identify new therapeutic targets to offer safer and more effective treatments.

Behaviorally penetrant, anomalous dopamine efflux exposes sex and circuit dependent regulation of dopamine transporters

Virtually all neuropsychiatric disorders display sex differences in prevalence, age of onset, and/or clinical symptomology. Although altered dopamine (DA) signaling is a feature of many of these disorders, sex-dependent mechanisms uniquely responsive to DA that drive sex-dependent behaviors remain unelucidated. Previously, we established that anomalous DA efflux (ADE) is a prominent feature of the DA transporter (DAT) variant Val559, a coding substitution identified in two male-biased disorders: attention-deficit/hyperactivity disorder and autism spectrum disorder. In vivo, Val559 ADE induces activation of nigrostriatal D2-type DA autoreceptors (D2ARs) that magnifies inappropriate, nonvesicular DA release by elevating phosphorylation and surface trafficking of ADE-prone DAT proteins. Here we demonstrate that DAT Val559 mice exhibit sex-dependent alterations in psychostimulant responses, social behavior, and cognitive performance. In a search for underlying mechanisms, we discovered that the ability of ADE to elicit D2AR regulation of DAT is both sex and circuit-dependent, with dorsal striatum D2AR/DAT coupling evident only in males, whereas D2AR/DAT coupling in the ventral striatum is exclusive to females. Moreover, systemic administration of the D2R antagonist sulpiride, which precludes ADE-driven DAT trafficking, can normalize DAT Val559 behavioral changes unique to each sex and without effects on the opposite sex or wildtype mice. Our studies support the sex- and circuit dependent capacity of D2ARs to regulate DAT as a critical determinant of the sex-biased effects of perturbed DA signaling in neurobehavioral disorders. Moreover, our work provides a cogent example of how a shared biological insult drives alternative physiological and behavioral trajectories as opposed to resilience.