Abstract

The present study was designed to examine effects of capsaicin administration on aggressive behaviors and autonomic thermoregulation in rats. In six-week-old rat, capsaicin was injected subcutaneously on 4 consecutive days in increasing doses(20mg/kg, 30mg/kg, 30mg/kg, 50mg/kg) to total of 150mg/kg of the drug. The controls were treated in the same way with vehicle alone. Two experments began six or eight weeks after the treatment. In experiment 1, isolation-induced agressive behaviors, scored a 10-min session in the dyadic situation, were significantly decreased by capsaicin pretreatment. This result was not in accord with the previous findings. In experiment 2, body temperature of the capsaicin-treated rats increased more than the control's at two amibient temperatures studied(37℃ and 40℃). Our result concerning thermoregulation supports the preceding studies that applied to the capsaicin-treated animals as neonate or adult. Thus, it is likely that the effect of capsaicin treatment on thermoregulation has nothing to do with the age of capsaicin injection. The capsaicin effects from this study were compared with hypothalamic lesion effects in the discussion part.