6-OHDA LESIONS TO AMYGDALA AND HIPPOCAMPUS ATTENUATE MEMORY-ENHANCINGEFFECT OF THE 3-7-FRAGMENT OF ANGIOTENSIN-II

We have previously shown that facilitatory effect of angiotensin II (A II) on the retrieval of memory is mediated by the dopaminergic system. In the present study, we searched for the influence of the 3-7 fragme nt of angiotensin II [AII(3-7)] on the retrieval processes in a passiv e avoidance situation after bilateral 6-OHDA lesions to the central am ygdala (CA) and the CA4 field of the hippocampus (HI). AII(3-7) given 15 min before the retention testing, at the intracerebroventricular do se of 1 nmol, significantly prolonged avoidance latencies in sham-oper ated rats (i.e. improved retrieval of memory for the electric footshoc k experienced during the learning trial). Bilateral lesions to CA tota lly abolished, and to HI significantly diminished, this facilitatory e ffect. An increase of spontaneous locomotor activity in rats lesioned to CA and a decrease in rats lesioned to HI were unlikely to interfere with the cognitive effect of AII (3-7). These results suggest that th e anatomical substrate of facilitating retrieval of information activi ty of AII(3-7) is closely related to the dopaminergic projection from the ventral tegmental area and substantia nigra to CA and HI. (C) 1998 Elsevier Science Inc.