Persisting changes in basolateral amygdala mRNAs after chronic ethanol consumption

Adolescent alcohol use is common and evidence suggests that early use may lead to an increased risk of later dependence. Persisting neuroadaptions in the amygdala as a result of chronic alcohol use have been associated with negative emotional states that may lead to increased alcohol intake. This study assessed the long-term impact of ethanol consumption on levels of several basolateral amygdala mRNAs in rats that consumed ethanol in adolescence or adulthood. Male Long-Evans rats were allowed restricted access to ethanol or water during adolescence (P28, n = 11, controls = 11) or adulthood (P80, n = 8, controls = 10) for 18 days. After a sixty day abstinent period, the brain was removed and sections containing the basolateral amygdala were taken. In situ hybridization was performed for GABA_A α₁, glutamic acid decarboxylase (GAD₆₇), corticotropin releasing factor (CRF), and N-methyl-d-aspartate (NMDA) NR2A mRNAs. A significant decrease was observed in GABA_A α₁, GAD₆₇, and CRF, but not NR2A, mRNAs in adult rats that consumed ethanol in comparison to controls. No significant changes were seen in adolescent consumers of ethanol for any of the probes tested. A separate analysis for each probe in the piriform cortex ascertained that the changes after ethanol consumption were specific to the basolateral amygdala. These results indicate that chronic ethanol consumption induces age-dependent alterations in basolateral amygdala neurochemistry.