?9-Tetrahydrocannabinol Experience Influences ?FosB and Downstream Gene Expression in Prefrontal Cortex.
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ABSTRACT: Introduction: Repeated administration of abused drugs, including ?9-tetrahydrocannabinol (THC), induces the stable transcription factor ?FosB in dopaminergic terminal field regions of the mesolimbic system. These studies investigated the effect of prior repeated THC treatment on THC-induced ?FosB expression and regulation of downstream targets in the forebrain. Methods: Mice received THC (10?mg/kg) or vehicle twice daily for 13 days, and then half of each group received a single injection of THC or vehicle 45?min before brain collection. ?FosB messenger RNA (mRNA) and protein were measured by polymerase chain reaction and immunoblotting, respectively. Potential downstream targets of ?FosB induction were measured by immunoblot. Results: THC injection in mice with a history of repeated THC treatment enhanced ?FosB expression as compared with vehicle in the prefrontal cortex (PFC), nucleus accumbens (NAc), and amygdala. This change occurred concomitantly with an increase in ?FosB mRNA in the PFC and NAc. THC injection in mice with a history of repeated THC treatment increased expression of cyclin-dependent kinase 5 (Cdk5) and its regulatory protein p35 only in the PFC. This increase in Cdk5 and p35 expression in PFC was also found in mice that had only received repeated THC administration, suggesting that this effect might be due to induction of ?FosB. Extracellular signal-regulated kinase (ERK) phosphorylation was increased in PFC after THC injection in repeated THC-treated mice. Phosphorylation of glycogen synthase kinase-3? (GSK3?), a Cdk5 target, was reduced in PFC after repeated THC treatment regardless of THC history, and phosphorylation of dopamine- and cAMP-regulated phosphoprotein of 32?kDa (DARPP-32) at the Cdk5-regulated threonine 75 site was unchanged. Conclusion: These results suggest that a history of repeated THC administration primes THC-mediated induction of ?FosB in the NAc and PFC, and that expression of both downstream targets of ?FosB (e.g., Cdk5 and p35) and upstream activators (e.g., pERK) in the PFC is dependent on THC history, which might have functional implications in addiction and neuropsychiatric disease.
SUBMITTER: Lazenka MF
PROVIDER: S-EPMC5628572 | biostudies-literature | 2017
REPOSITORIES: biostudies-literature
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