Abstract
Substance use disorder is driven by complex gene-environment interactions. Epigenetic histone regulation is a significant contributor to several behavioral phenotypes of drug abuse. The primary epigenetic mechanisms that drive drug taking and drug seeking are still being investigated, and it is unclear how environmental conditions alter epigenetic histone acetylation to change behaviors geared toward drug reward. This study examined the effects of environmental condition on amphetamine self-administration, and whether drug-taking and drug-seeking behaviors could be influenced through inhibition of an epigenetic regulator, histone deacetylase (HDAC). Male rats reared for 30 days in enriched (EC), isolated (IC), or standard conditions (SC) prior to amphetamine (0.03, 0.05, 0.1 mg/kg/infusion, IV) self-administration, extinction, and reinstatement sessions. The HDAC inhibitor, Trichostatin A (TsA; 0.3 mg/kg, IV), was injected 30 min prior to operant sessions. After amphetamine-induced reinstatement (0.25 mg/kg, subcutaneous [s.c.]), tissue was extracted for Western blot analyses of acetylated histone H3 lysine 9 (acH3K9) in the nucleus accumbens (NAc) and dorsal striatum (DSt). While TsA did not significantly affect amphetamine self-administration or extinction, TsA decreased cue-, but not drug-induced reinstatement in IC rats only. In the DSt, but not in the NAc, IC rats exhibited significantly less acH3K9 expression than EC and SC rats, irrespective of TsA treatment. HDAC inhibition decreases cue-induced reinstatement of amphetamine seeking in IC rats. While IC rats exhibit less acH3K9 expression in the DSt, future studies are needed to elucidate the critical epigenetic factors that drive substance abuse, particularly in vulnerable populations. (PsycINFO Database Record (c) 2019 APA, all rights reserved).