Chronic anabolic-androgenic steroid treatment during adolescence increasesanterior hypothalamic vasopressin and aggression in intact hamsters

The present study examines the hypothesis that exposure to anabolic-androge nic steroids (AAS) during adolescent development predisposes hamsters to he ightened levels of aggressive behavior by influencing the anterior hypothal amic-arginine vasopressin (AH-AVP) neural system. To test this, adolescent male hamsters (Mesocricetus auratus) were treated with high doses of AAS, t ested for offensive aggression in the absence or presence of AH-AVP recepto r antagonists, and then examined for changes in AH-AVP expression and neura l organization. AAS exposure during adolescence significantly increased agg ression intensity (number of attacks and bites) and initiation (latency to the first bite). Yet, only increases in aggression intensity were inhibited by AH-AVP receptor antagonism. Adolescent AAS-treated hamsters showed sign ificant increases in AH-AVP fiber density and peptide content. However, no alterations in AH-AVP neuronal organization or mRNA expression were found. Together, these data suggest that adolescent AAS exposure increase aggressi on intensity by altering AH-AVP expression and activity, providing direct e vidence for a causal role of AH-AVP expression and function in early onset AAS-stimulated aggression. (C) 2000 Elsevier Science Ltd. All rights reserv ed.