Hippocampal cholineacetyltransferase activity, agonistic behaviour and social stress in male rabbits.

Agonistic behaviour was observed in pairs of unfamiliar male rabbits living in an outdoor enclosure. Attack, Chase, Follow and Cross-over were scored. On the basis of their frequencies the subjects in the pair were assigned a first or second rank-position. Hippocampal cholineacetyltransferase (ChAT) and plasma levels of corticosterone were considered in relation to rank. ChAT levels in the dorsal hippocampus varied in relation to agonistic behaviour. Second-ranking subjects had significantly higher levels of ChAT than the first-ranking animals and had levels of corticosterone which were markedly higher at the end of the experimental period than at the beginning. A negative correlation was found between Attack and ChAT levels in the dorsal hippocampus. These results suggest the presence of social stress in the second-ranking animals and indicate a state of activation of the hippocampus in relation to agonistic behaviour.