EXPRESSION OF TESTOSTERONE CONDITIONED PLACE PREFERENCE IS BLOCKED BYPERIPHERAL OR INTRAACCUMBENS INJECTION OF ALPHA-FLUPENTIXOL

Previous evidence indicates that peripheral and intranucleus accumbens injections of testosterone have rewarding effects in male rats as mea sured in a conditioned place preference (CPP) paradigm. The present st udy investigated the neurochemical bases of the rewarding properties o f testosterone by examining the effect of peripheral and intranucleus accumbens injection of the dopamine receptor antagonist alpha-flupenth ixol on expression of testosterone-induced CPP. On alternating days, a dult male Long-Evans rats received peripheral injections of testostero ne in a water-soluble hydroxypropyl-beta-cyclodextrin (HBC) inclusion complex (0.8 mg/kg) or saline-HBC immediately prior to being confined for 30 min to one of two compartments of a place preference apparatus. All rats received 8 days of pairings (four hormone pairings, four sal ine pairings). On day 9 the rats were given a 20-min test session duri ng which they had access to all compartments of the apparatus. No horm one was injected prior to the test session; however, rats received a p eripheral (20 min prior; 0.2, 0.3 mg/kg) or intra-accumbens (2 min pri or, 5.0 mu g) injection of cu-flupenthixol or saline. On the test day, rats receiving saline injections spent significantly more time in the compartment previously paired with injections of testosterone than in the compartment previously paired with vehicle injections. In contras t, rats receiving peripheral or intra-accumbens alpha-flupenthixol inj ections did not spend significantly more time in the compartment previ ously paired with testosterone. The blockade of testosterone CPP was n ot due to an effect of cu-flupenthixol on motor behavior. The findings provide further evidence of the rewarding affective properties of tes tosterone and indicate that peripheral administration and intra-accumb ens administration of alpha-flupenthixor block expression of testoster one CPP. The rewarding affective properties of testosterone are mediat ed, at least in part, via an interaction with the mesolimbic dopamine system. (C) 1998 Academic Press.