Growth hormone and isolation-induced aggression in wild male mice.

Aggressive behavior, motor activity and defecation were examined simultaneously in wild male mice following daily growth hormone (GH) administration. GH was found to increase isolation-induced aggression by increasing fighting duration and decreasing latency to fight. There was no influence on non-aggressive motor activity nor on the defecation rate, a presumed parameter of emotionality. The results provide evidence of behavioral properties of GH. The mechanism of this action is discussed in terms of a possible direct central action of GH, not mediated by glucagon, insulin, secretin and gastrin.