ALTERATIONS IN SEROTONIN(1B) (5HT(1B)) RECEPTOR SUBTYPES IN THE BRAINOF ETHANOL-TREATED RATS

The effects of acute or chronic ethanol treatment and of withdrawal (2 4 h) after chronic ethanol treatment on 5HT(1B) receptor subtypes in d ifferent regions of the rat brain were investigated. Male Sprague-Dawl ey rats were fed the ethanol (9% v/v)-containing Lieber-DeCarli liquid diet or the control liquid diet for 1 day in the acute study and for 15 days in the chronic study. The ethanol-withdrawn group received the Lieber-DeCarli control liquid diet instead of the ethanol diet on the 15th night. Ethanol-withdrawn rats after 15 days of ethanol treatment were rated for withdrawal symptoms (e.g. hyperactivity, piloerection, squealing, and enhanced startle reflex) and were found to exhibit suc h symptoms after 24 h of ethanol withdrawal. The rats were decapitated , and cortices, cerebelli, striata, and hippocampi were separated for measurement of 5HT(1B) receptors by receptor binding techniques using I-125-cyanopindolol (CYP) as the ligand. It was observed that acute et hanol treatment had no significant effect on the maximum number of bin ding sites (B-max) or the apparent dissociation constant (K-D) of 5HT( 1B) receptor binding sites in the various brain regions. On the other hand, chronic ethanol treatment produced a significant increase in B-m ax of I-125-CYP binding to 5HT(1B) receptors in the rat cortex and hip pocampus, which remained increased after 24 h of ethanol withdrawal. I n contrast, in the striatum and the cerebellum of chronic ethanol-trea ted and withdrawn rats, the 5HT(1B) binding parameters (B-max and K-D) were unchanged. These results suggest the possible involvement of cor tical and hippocampal 5HT(1B) receptors in ethanol dependence.