Neuropsychiatric Sequelae in Adolescents With Acute Synthetic Cannabinoid Toxicity.

BACKGROUND AND OBJECTIVES: Adolescents represent the largest age group that presents to emergency departments (ED) for synthetic cannabinoid (SC) toxicity; however, the neurotoxic effects of acute SC exposures in this group are understudied. Our aim was to characterize the neuropsychiatric presentation of adolescents with SC-related exposure in the ED compared with those with traditional cannabis exposure. METHODS: A multicenter registry of clinical information prospectively collected by medical toxicologists (Toxicology Investigators Consortium Case Registry) was reviewed for adolescents presenting to the ED after SC or cannabis exposure from 2010 through 2018. Associations were measured between drug exposures and neuropsychiatric symptoms and/or signs. Exposures were classified into 4 groups: SC-only exposure, SC-polydrug exposures, cannabis-only exposure, and cannabis-polydrug exposures. RESULTS: Adolescents presenting to the ED with SC-only exposure (n = 107) had higher odds of coma and/or central nervous system depression (odds ratio [OR] 3.42; 95% confidence interval [CI] 1.51-7.75) and seizures (OR 3.89; 95% CI 1.39-10.94) than those with cannabis-only exposure (n = 86). SC-only drug exposure was associated with lower odds of agitation than cannabis-only exposure (OR 0.18; 95% CI 0.10-0.34). In contrast, the group with SC-polydrug exposures (n = 38) had higher odds of agitation (OR 3.11; 95% CI 1.56-7.44) and seizures (OR 4.8; 95% CI 1.80-12.74) than the cannabis-polydrug exposures group (n = 117). CONCLUSIONS: In this multisite cohort of US adolescents assessed in the ED, SC exposure was associated with higher odds of neuropsychiatric morbidity than cannabis exposure providing a distinct neurospychiatric profile of acute SC toxicity in adolescents.

Epigenetic basis of opiate suppression of Bdnf gene expression in the ventral tegmental area.

Brain-derived neurotrophic factor (BDNF) has a crucial role in modulating neural and behavioral plasticity to drugs of abuse. We found a persistent downregulation of exon-specific Bdnf expression in the ventral tegmental area (VTA) in response to chronic opiate exposure, which was mediated by specific epigenetic modifications at the corresponding Bdnf gene promoters. Exposure to chronic morphine increased stalling of RNA polymerase II at these Bdnf promoters in VTA and altered permissive and repressive histone modifications and occupancy of their regulatory proteins at the specific promoters. Furthermore, we found that morphine suppressed binding of phospho-CREB (cAMP response element binding protein) to Bdnf promoters in VTA, which resulted from enrichment of trimethylated H3K27 at the promoters, and that decreased NURR1 (nuclear receptor related-1) expression also contributed to Bdnf repression and associated behavioral plasticity to morphine. Our findings suggest previously unknown epigenetic mechanisms of morphine-induced molecular and behavioral neuroadaptations.

Impaired periamygdaloid-cortex prodynorphin is characteristic of opiate addiction and depression.

Negative affect is critical for conferring vulnerability to opiate addiction as reflected by the high comorbidity of opiate abuse with major depressive disorder (MDD). Rodent models implicate amygdala prodynorphin (Pdyn) as a mediator of negative affect; however, evidence of PDYN involvement in human negative affect is limited. Here, we found reduced PDYN mRNA expression in the postmortem human amygdala nucleus of the periamygdaloid cortex (PAC) in both heroin abusers and MDD subjects. Similar to humans, rats that chronically self-administered heroin had reduced Pdyn mRNA expression in the PAC at a time point associated with a negative affective state. Using the in vivo functional imaging technology DREAMM (DREADD-assisted metabolic mapping, where DREADD indicates designer receptors exclusively activated by designer drugs), we found that selective inhibition of Pdyn-expressing neurons in the rat PAC increased metabolic activity in the extended amygdala, which is a key substrate of the extrahypothalamic brain stress system. In parallel, PAC-specific Pdyn inhibition provoked negative affect-related physiological and behavioral changes. Altogether, our translational study supports a functional role for impaired Pdyn in the PAC in opiate abuse through activation of the stress and negative affect neurocircuitry implicated in addiction vulnerability.

Whole-brain circuit dissection in free-moving animals reveals cell-specific mesocorticolimbic networks.

The ability to map the functional connectivity of discrete cell types in the intact mammalian brain during behavior is crucial for advancing our understanding of brain function in normal and disease states. We combined designer receptor exclusively activated by designer drug (DREADD) technology and behavioral imaging with µPET and [18F]fluorodeoxyglucose (FDG) to generate whole-brain metabolic maps of cell-specific functional circuits during the awake, freely moving state. We have termed this approach DREADD-assisted metabolic mapping (DREAMM) and documented its ability in rats to map whole-brain functional anatomy. We applied this strategy to evaluating changes in the brain associated with inhibition of prodynorphin-expressing (Pdyn-expressing) and of proenkephalin-expressing (Penk-expressing) medium spiny neurons (MSNs) of the nucleus accumbens shell (NAcSh), which have been implicated in neuropsychiatric disorders. DREAMM revealed discrete behavioral manifestations and concurrent engagement of distinct corticolimbic networks associated with dysregulation of Pdyn and Penk in MSNs of the NAcSh. Furthermore, distinct neuronal networks were recruited in awake versus anesthetized conditions. These data demonstrate that DREAMM is a highly sensitive, molecular, high-resolution quantitative imaging approach.