POSTTRAINING ADMINISTRATION OF SUBSTANCE-P AND ITS N-TERMINAL FRAGMENT BLOCK THE AMNESTIC EFFECTS OF DIAZEPAM

This study examined the effects of posttraining administration of subs tance P (SP) and of certain N- or C-terminal SP-fragments on retention performance of rats treated with diazepam (DZP). Twenty minutes befor e the training on an inhibitory avoidance task rats were given intrape ritoneal injections of either DZP (2 mg/kg) or vehicle. Immediately af ter they were injected with SP (50 mu g/kg), SPN 1-7 (167 mu g/kg), SP C 6-11 (134 mu g/kg), or vehicle. The posttrial administration of SP a nd SPN, but not SPC, facilitated avoidance behavior. Animals that rece ived DZP before training and vehicle after the conditioning trial show ed impaired retention. In contrast, in animals injected with SP and SP N after the training trial, DZP did not affect retention. These findin gs suggest that the amnestic effects of DZP can be blocked by the admi nistration of SP and that the amino acid sequence responsible for this effect may be encoded by its N-terminal part. (C) 1998 Academic Press .