Angiotensin II (3-8) induces long-term memory improvement in the crab Chasmagnathus.

A shadow moving overhead acts as a danger stimulus and elicits an escape response in the crab Chasmagnathus that habituates after 15 trials and for a long period of time. Previous work showed that angiotensin II enhances this long-term memory. Present results indicate: (1) that the facilitatory effect of angiotensin II is not blocked by either losartan, DUP 753 or the Parke Davis compound PD 123177; (2) that the angiotensin II (3-8) fragment has an enhancing effect on crab's memory stronger than that reported for the integer octopeptide; (3) that the hypermnestic effect of angiotensin II (3-8) is dose-dependent and saralasin reversible. The possibility that the action of angiotensin II on crab's memory were not due to its own action but to that of the degradation fragment angiotensin II (3-8) is discussed.