Alterations in anterior hypothalamic vasopressin, but not serotonin, correlate with the temporal onset of aggressive behavior during adolescent anabolic-androgenic steroid exposure in hamsters (Mesocricetus auratus)

In hamsters (Mesocricetus auratus), anabolic-androgenic steroid (AAS) exposure during adolescence facilitates offensive aggression that is correlated with the enhanced development of the arginine vasopressin (AVP) neural system and reduced development of the serotonin (5-HT) neural system in the anterior hypothalamus (AH). This study examined the temporal onset of these effects by measuring aggression and AH AVP and 5-HT during progressively shorter periods of AAS exposure during adolescent development. The authors tested adolescent hamsters that received AAS for 3, 7, 14, or 28 days for offensive aggression and then examined the hamsters for AVP/5-HT afferent innervation to the AH using immunohistochemistry. While reductions in AH 5-HT afferent innervation were detectable by 7 days of AAS exposure, no concomitant increases in offensive aggression were observed compared to oil-treated littermates. In contrast, by Day 14 of AAS treatment, AH AVP and offensive aggression were significantly higher than oil-treated controls. These data indicate that relatively short-term adolescent AAS exposure alters aggression and AH 5-HT and AVP development, yet only alterations in AH AVP development correlate with temporal onset of the aggressive behavioral phenotype during adolescent AAS exposure.