Effect on memory processes of anti-vasopressin serum microinjected into the dorsal raphe nucleus: the role of catecholaminergic neurotransmission.

Anti-arginine8-vasopressin serum was microinjected into the mesencephalic dorsal raphe nucleus immediately after the learning trial, in a one-trial learning passive avoidance reaction. The treatment attenuated passive avoidance behavior 24 h after treatment, suggesting a role of the endogenous vasopressin of this area in memory processes. On the other hand, the antiserum did not influence passive avoidance behavior if 6-hydroxydopamine was microinjected into the raphe region. The data suggest that the antiserum may have primarily interacted with catecholaminergic terminals, which enter the dorsal raphe nucleus.