SEROTONIN AGONIST-INDUCED DECREASES IN INTERMALE AGGRESSION ARE DEPENDENT ON BRAIN REGION AND RECEPTOR SUBTYPE

Testosterone (T) and its androgenic and estrogenic metabolites modulat e the ability of serotonin (5-HT)(1A) and 5-HT1B agonists to inhibit i ntermale aggressive behavior. This study tested whether the lateral se ptum (LS) and medial preoptic area (MPG), which an part of the neuroan atomical substrate for aggression and contain androgen, estrogen, 5-HT 1A and 5-HT1B receptors, represent sites where these modulatory effect s occur. Gonadectomized CF-1 male mice were given silastic implants co ntaining diethylstilbestrol (DES, a synthetic estrogen) or dihydrotest osterone (DHT, a nonaromatizable androgen) and implanted bilaterally w ith guide cannula directed at the LS or MPO. They were microinjected w ith either CGS12066B, a 5-HT1B agonist (400 mu M LS, 200 mu M MPO); 8- hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), a 5-HT1A agonist (10 mu M LS, 5 mu M MPO); or combined CGS + 8-OH-DPAT treatment and teste d for aggression 15 min later. When microinjections were given in the LS, androgen-treated males exhibited significantly reduced attack beha vior in response to CGS or to CGS + 8-OH-DPAT. The attack behavior of DES-treated males was not reduced by any of the treatments. In contras t, all agonist treatments decreased aggression when injected into the MPO in both hormone conditions. The findings demonstrate regional vari ation in the ability of androgens and estrogens to modulate S-HT1A- an d 5-HT1B-agonist mediated reductions in aggression. (C) 1997 Elsevier Science Inc.