Influence of p-chloroamphetamine and methysergide on the escape deficits provoked by inescapable shock.

The effects of serotonergic manipulations on the escape interference engendered by exposure to inescapable shock were assessed. Consistent with the view that the behavioral interference was related to reductions of serotonin (5-HT), treatment with the 5-HT receptor blocker methysergide mimicked the effects of inescapable shock in that it increased escape latencies. Conversely, acute treatment with a moderate dose of the 5-HT releasing agent p-chloroamphetamine (PCA) effectively antagonized the escape interference ordinarily provoked by inescapable shock. The effects of PCA were behaviorally distinguishable from the previously observed effects of catecholamine stimulants. Whereas catecholamine stimulants applied prior to either inescapable shock or escape testing eliminated the interference, PCA antagonized the behavioral disruption only if it was administered before testing. It is suggested that catecholamine alterations may be fundamental in the provocation of the interference, whereas 5-HT variations may contribute to the expression of the behavioral disturbance.