Psychotropic effects of angiotensin II and III in rats: locomotor and exploratory vs cognitive behaviour.

One nmol of angiotensin II (AII) or angiotensin III (AIII) given intracerebroventricularly (i.c.v.) increased locomotor and exploratory activity in an open field apparatus but not in the electromagnetic field motimeter. Both peptides significantly enhanced stereotyped behaviour produced by apomorphine (2 mg/kg) and amphetamine (6.5 mg/kg) given intraperitoneally. Also, AII and AIII improved consolidation but not retrieval of memory for an appetitively reinforced spatial discrimination task in a T-maze. AII as well as AIII, given prior to the learning session on day 1, increased rate of acquisition of conditioned avoidance responses in a shuttle-box over the next 7 days. Both angiotensins, injected i.c.v. 15 min before the retention testing, remarkably (5-fold) prolonged re-entry latencies in the passive avoidance situation, suggesting facilitation of the retrieval of memory for an aversively motivated behaviour.