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Despite the belief that cannabis is relatively harmless, exposure during adolescence is associated with increased risk of developing several psychopathologies in adulthood. In addition to the high levels of use amongst teenagers, the potency of ∆-9-tetrahydrocannabinol (THC) has increased more than fourfold compared to even twenty years ago, and it is unclear whether potency influences the presentation of THC-induced behaviors. Expanded knowledge about the impact of adolescent THC exposure, especially high dose, is important to delineating neural networks and molecular mechanisms underlying psychiatric risk. Here, we observed that repeated exposure to low (1.5 mg/kg) and high (5 mg/kg) doses of THC during adolescence in male rats produced divergent effects on behavior in adulthood. Whereas low dose rats showed greater sensitivity to reward devaluation and also self-administered more heroin, high dose animals were significantly more reactive to social isolation stress. RNA sequencing of the basolateral amygdala, a region linked to reward processing and stress, revealed significant perturbations in transcripts and gene networks related to synaptic plasticity and HPA axis that were distinct to THC dose as well as stress. In silico single-cell deconvolution of the RNAseq data revealed a significant reduction of astrocyte-specific genes related to glutamate regulation in stressed high dose animals, a result paired anatomically with greater astrocyte-to-neuron ratios and hypotrophic astrocytes. These findings emphasize the importance of dose and behavioral state on the presentation of THC-related behavioral phenotypes in adulthood and dysregulation of astrocytes as an interface for the protracted effects of high dose THC and subsequent stress sensitivity., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

Prenatal stress can lead to long-term adverse effects that increase the risk of anxiety and other emotional disorders in offspring. The in utero underpinnings contributing to such phenotypes remain unknown. We profiled the transcriptome of placental specimens from women who lived through Hurricane Sandy during pregnancy compared to those pregnant during non-Sandy conditions. Following birth, longitudinal assessments were conducted in their offspring during childhood (~3-4 years old) to measure steroid hormones (in hair) and behavioral and emotional problems. This revealed a significant link between prenatal Sandy stress (PNSS) and child HPA dysfunction, evident by altered cortisol, dehydroepiandrosterone (DHEA), and cortisol:DHEA levels. In addition, PNSS was associated with significantly increased anxiety and aggression. These findings coincided with significant reorganization of the placental transcriptome via vascular, immune, and endocrine gene pathways. Interestingly, many of the most prominently altered genes were known to be uniquely expressed in syncytiotrophoblast (STB)-subtype of placental cells and harbored glucocorticoid response elements in promoter regions. Finally, several vascular development- and immune-related placental gene sets were found to mediate the relationship between PNSS and childhood phenotypes. Overall, these findings suggest that natural disaster-related stress during pregnancy reprograms the placental molecular signature, potentially driving long-lasting changes in stress regulation and emotional health. Further examination of placental mechanisms may elucidate the environment's contribution to subsequent risk for anxiety disorders later in life., (© 2021. The Author(s), under exclusive licence to Springer Nature Limited.)

Consumption of high fat, high sugar (western) diets is a major contributor to the current high levels of obesity. Here, we used a multidisciplinary approach to gain insight into the molecular mechanisms underlying susceptibility to diet-induced obesity (DIO). Using positron emission tomography (PET), we identified the dorsal striatum as the brain area most altered in DIO-susceptible rats and molecular studies within this region highlighted regulator of G-protein signaling 4 (Rgs4) within laser-capture micro-dissected striatonigral (SN) and striatopallidal (SP) medium spiny neurons (MSNs) as playing a key role. Rgs4 is a GTPase accelerating enzyme implicated in plasticity mechanisms of SP MSNs, which are known to regulate feeding and disturbances of which are associated with obesity. Compared to DIO-resistant rats, DIO-susceptible rats exhibited increased striatal Rgs4 with mRNA expression levels enriched in SP MSNs. siRNA-mediated knockdown of striatal Rgs4 in DIO-susceptible rats decreased food intake to levels comparable to DIO-resistant animals. Finally, we demonstrated that the human Rgs4 gene locus is associated with increased body weight and obesity susceptibility phenotypes, and that overweight humans exhibit increased striatal Rgs4 protein. Our findings highlight a novel role for involvement of Rgs4 in SP MSNs in feeding and DIO-susceptibility.

Delineating the pathophysiology of psychiatric disorders has been extremely challenging but technological advances in recent decades have facilitated a deeper interrogation of molecular processes in the human brain. Initial candidate gene expression studies of the postmortem brain have evolved into genome wide profiling of the transcriptome and the epigenome, a critical regulator of gene expression. Here, we review the potential and challenges of direct molecular characterization of the postmortem human brain, and provide a brief overview of recent transcriptional and epigenetic studies with respect to neuropsychiatric disorders. Such information can now be leveraged and integrated with the growing number of genome-wide association databases to provide a functional context of trait-associated genetic variants linked to psychiatric illnesses and related phenotypes. While it is clear that the field is still developing and challenges remain to be surmounted, these recent advances nevertheless hold tremendous promise for delineating the neurobiological underpinnings of mental diseases and accelerating the development of novel medication strategies.

Neuronal circuits within the prefrontal cortex (PFC) mediate higher cognitive functions and emotional regulation that are disrupted in psychiatric disorders. The PFC undergoes significant maturation during adolescence, a period when cannabis use in humans has been linked to subsequent vulnerability to psychiatric disorders such as addiction and schizophrenia. Here, we investigated in a rat model the effects of adolescent exposure to Δ 9 -tetrahydrocannabinol (THC), a psychoactive component of cannabis, on the morphological architecture and transcriptional profile of layer III pyramidal neurons-using cell type- and layer-specific high-resolution microscopy, laser capture microdissection and next-generation RNA-sequencing. The results confirmed known normal expansions in basal dendritic arborization and dendritic spine pruning during the transition from late adolescence to early adulthood that were accompanied by differential expression of gene networks associated with neurodevelopment in control animals. In contrast, THC exposure disrupted the normal developmental process by inducing premature pruning of dendritic spines and allostatic atrophy of dendritic arborization in early adulthood. Surprisingly, there was minimal overlap of the developmental transcriptomes between THC- and vehicle-exposed rats. THC altered functional gene networks related to cell morphogenesis, dendritic development, and cytoskeleton organization. Marked developmental network disturbances were evident for epigenetic regulators with enhanced co-expression of chromatin- and dendrite-related genes in THC-treated animals. Dysregulated PFC co-expression networks common to both the THC-treated animals and patients with schizophrenia were enriched for cytoskeletal and neurite development. Overall, adolescent THC exposure altered the morphological and transcriptional trajectory of PFC pyramidal neurons, which could enhance vulnerability to psychiatric disorders.

Impulsivity, a multifaceted behavioral hallmark of attention-deficit/hyperactivity disorder (ADHD), strongly influences addiction vulnerability and other psychiatric disorders that incur enormous medical and societal burdens yet the neurobiological underpinnings linking impulsivity to disease remain poorly understood. Here we report the critical role of ventral striatal cAMP-response element modulator (CREM) in mediating impulsivity relevant to drug abuse vulnerability. Using an ADHD rat model, we demonstrate that impulsive animals are neurochemically and behaviorally more sensitive to heroin and exhibit reduced Crem expression in the nucleus accumbens core. Virally increasing Crem levels decreased impulsive action, thus establishing a causal relationship. Genetic studies in seven independent human populations illustrate that a CREM promoter variant at rs12765063 is associated with impulsivity, hyperactivity and addiction-related phenotypes. We also reveal a role of Crem in regulating striatal structural plasticity. Together, these results highlight that ventral striatal CREM mediates impulsivity related to substance abuse and suggest that CREM and its regulated network may be promising therapeutic targets.

The bed nucleus of the stria terminalis (BNST) is a brain region important for regulating anxiety-related behavior in both humans and rodents. Here we used a chemogenetic strategy to investigate how engagement of G protein-coupled receptor (GPCR) signaling cascades in genetically defined GABAergic BNST neurons modulates anxiety-related behavior and downstream circuit function. We saw that stimulation of vesicular γ-aminobutyric acid (GABA) transporter (VGAT)-expressing BNST neurons using hM3Dq, but neither hM4Di nor rM3Ds designer receptors exclusively activated by a designer drug (DREADD), promotes anxiety-like behavior. Further, we identified that activation of hM3Dq receptors in BNST VGAT neurons can induce a long-term depression-like state of glutamatergic synaptic transmission, indicating DREADD-induced changes in synaptic plasticity. Further, we used DREADD-assisted metabolic mapping to profile brain-wide network activity following activation of G q -mediated signaling in BNST VGAT neurons and saw increased activity within ventral midbrain structures, including the ventral tegmental area and hindbrain structures such as the locus coeruleus and parabrachial nucleus. These results highlight that G q -mediated signaling in BNST VGAT neurons can drive downstream network activity that correlates with anxiety-like behavior and points to the importance of identifying endogenous GPCRs within genetically defined cell populations. We next used a microfluidics approach to profile the receptorome of single BNST VGAT neurons. This approach yielded multiple G q -coupled receptors that are associated with anxiety-like behavior and several potential novel candidates for regulation of anxiety-like behavior. From this, we identified that stimulation of the G q -coupled receptor 5-HT 2C R in the BNST is sufficient to elevate anxiety-like behavior in an acoustic startle task. Together, these results provide a novel profile of receptors within genetically defined BNST VGAT neurons that may serve as therapeutic targets for regulating anxiety states and provide a blueprint for examining how G-protein-mediated signaling in a genetically defined cell type can be used to assess behavior and brain-wide circuit function.

Opioid drugs are highly addictive and their abuse has a strong genetic load. Dopamine-glutamate interactions are hypothesized to be important for regulating neural systems central for addiction vulnerability. Balanced dopamine-glutamate interaction is mediated through several functional associations, including a physical link between discs, large homolog 4 (Drosophila) (DLG4, PSD-95) and dopamine receptor 1 (DRD1) within the postsynaptic density to regulate DRD1 trafficking. To address whether genetic associations with heroin abuse exist in relation to dopamine and glutamate and their potential interactions, we evaluated single-nucleotide polymorphisms of key genes within these systems in three populations of opiate abusers and controls, totaling 489 individuals from Europe and the United States. Despite significant differences in racial makeup of the separate samples, polymorphisms of DRD1 and DLG4 were found to be associated with opiate abuse. In addition, a strong gene-gene interaction between homer 1 homolog (Drosophila) (HOMER1) and DRD1 was predicted to occur in Caucasian subjects. This interaction was further analyzed by evaluating DRD1 genotype in relation to HOMER1b/c protein expression in postmortem tissue from a subset of Caucasian subjects. DRD1 rs265973 genotype correlated with HOMER1b/c levels in the striatum, but not cortex or amygdala; the correlation was inversed in opiate abusers as compared with controls. Cumulatively, these results support the hypothesis that there may be significant, genetically influenced interactions between glutamatergic and dopaminergic pathways in opiate abusers.

The dynorphin system has been associated with the regulation of mood. The expression of the prodynorphin mRNA was currently studied in the amygdaloid complex, a brain region critical for emotional processing, in subjects (14-15 per group) diagnosed with major depression, bipolar disorder, or schizophrenia and compared to normal controls. In situ hybridization histochemistry was used to characterize the anatomical distribution and expression levels of the prodynorphin mRNA within the amygdaloid complex. High prodynorphin mRNA levels were expressed in the parvicellular division of the accessory basal, posterior cortical, periamygdaloid cortex, and amygdalohippocampal area in normal subjects. Individuals with major depression had significantly reduced (41-68%) expression of the prodynorphin mRNA in the accessory basal (both parvicellular and magnocellular divisions; P < 0.01) and amygdalohippocampal area (P < 0.001) as compared to controls. The bipolar disorder group also showed a significant reduction (37-38%, P < 0.01) of the mRNA expression levels in the amygdalohippocampal area and in the parvicellular division of the accessory basal. No other amygdala nuclei studied showed any significant differences for the prodynorphin mRNA levels measured in the major depression and bipolar disorder subjects. Additionally, the prodynorphin mRNA expression levels did not differ significantly between the schizophrenic and normal control subjects in any of the amygdala areas examined. These findings indicate specific prodynorphin amygdala impairment in association with mood disorder.

Experimental and clinical studies suggest an involvement of the opioid neuropeptide system in psychiatric disorders. Notably, opioid peptide immunoreactivity is altered in the cerebrospinal fluid of chronic schizophrenics and manic-depressive subjects. Despite these clinical findings, few postmortem investigations have examined the association of endogenous opioid neuropeptides with schizophrenia and suicide. Anatomically, a tight interaction exists within the neostriatum between the opioid peptide (dynorphin and enkephalin) system and classical neurotransmitters such as dopamine which has been implicated in both the psychotic symptoms and the cognitive deficits that characterize schizophrenia (see review). The neostriatum is differentially organized into patch and matrix neurochemical mosaic compartments anatomically connected to limbic- and sensorimotor-related brain regions, respectively. Moreover, the human neostriatum is characterized by a heterogenous expression of the prodynorphin opioid gene: high in the patch, but low in the matrix compartment. The present results show for the first time a differential alteration of prodynorphin within distinct striatal compartments in postmortem tissue from nonschizophrenic suicide subjects. The prodynorphin patch/matrix mRNA expression was elevated in the caudate nucleus of suicide subjects as compared to normal controls and schizophrenics in which no alterations in opioid peptides or D1 and D2 mRNA expression were apparent. Altogether the findings suggest that discrete dysfunction of the endogenous opioid dynorphin system might contribute to depression and the risk of suicide in nonschizophrenic subjects.