The persistence of hyperresponsiveness to apomorphine in rats following REM sleep deprivation and the influence of housing conditions

Abstract

The hyperresponsiveness to apomorphine disappears after REM sleep deprivation of rats; the time course of the disappearance was investigated. When REM sleep-deprived (REMd) rats were caged individually during the recovery period the increase in ambulation and in stereotyped behaviour elicited by apomorphine subsided within 8-24 h; on the other hand, the exaggerated aggressiveness persisted up to 64 days. However, when the deprived rats were allowed to recovery in groups of 3 per cage the increase in aggressiveness subsided after 4 days. Since individual housing of non-deprived rats for 4--11 days increased the apomorphine-aggressiveness steadily, 'isolation' probably summed with REM deprivation in facilitating the effects of apomorphine on aggressive behaviour. The results also suggest that the dopaminergic systems implicated in aggressive behaviour are sensitized by REM deprivation for a longer period than those subjacent to ambulation and stereotype.