Alcohol reinstatement after prolonged abstinence from alcohol drinking by female adolescent rats: Roles of cyclooxygenase-2 and the prostaglandin E₂ receptor 1.

Abstract

Adolescent alcohol misuse is a global problem that can significantly increase the reinstatement of alcohol drinking during re-exposure after abstinence, but the mechanism that causes this increase is unknown. Female adolescents are an understudied population but they are particularly vulnerable to adolescent-onset alcohol abuse. We aimed to determine how adolescent-onset alcohol drinking affects pro-inflammatory mediators endothelin-1 (ET-1), cyclooxygenase-2 (COX-2), and prostaglandin E₂ (PGE₂) in the brain and the role of COX-2 and PGE₂ in EtOH reinstatement in adolescent females. Adolescent female rats were exposed to a 2-bottle choice paradigm of water vs 5% ethanol (EtOH) every other day over a 21 day period. ET-1 and COX-2 proteins were measured in the dorsal striatum (DS) after a 4 week abstinence from EtOH drinking. The COX-2 inhibitor nimesulide was then administered during abstinence prior to an EtOH reinstatement or sucrose preference or to measure PGE₂ content. The PGE₂ receptor 1 (EP₁) antagonist SC-51089 was then administered prior to EtOH reinstatement during which EtOH intake was measured. EtOH drinking significantly increased ET-1 by 33.8 ± 8.9% and COX-2 by 71.4 ± 24.3% in the DS. Treatment with nimesulide during abstinence attenuated EtOH intake during reinstatement after prolonged abstinence by 40.3 ± 12.4% compared to saline controls. Adolescent EtOH drinking and abstinence increased PGE₂ 150.5 ± 30.9% in the DS and nimesulide attenuated this increase. SC-51089 treatment during abstinence attenuated EtOH reinstatement by 48.1 ± 8.4% compared to DMSO controls. These experiments identified a prostaglandin-mediated mechanism that offers a putative pharmacological target to attenuate EtOH reinstatement after adolescent-onset EtOH drinking.