Dopaminergic Projection to the Nucleus Accumbens Mediates the Memory-Enhancing Effect of Angiotensins in Rats

Abstract

It has been shown that the facilitatory effect of angiotensin II (AII) and its 3–7 fragment [AII(3–7)] on cognitive processes is mediated by the dopaminergic system. In the present study, the involvement of dopaminergic projection to the nucleus accumbens (NAS) and to the nucleus septi lateralis (NSL) in the expression of the positive effect of AII and AII(3–7) on the retrieval of passive avoidance after bilateral 6-OHDA induced lesions to NAS and NSL was evaluated. To protect noradrenergic neurons from destruction by neurotoxin, rats were pretreated intraperitoneally with 25 mg/kg of desmethylimipramine, an inhibitor of noradrenaline uptake, 30 min before surgery. Both peptides were given intracerebroventricularly, at the dose of 1 nmol each, 15 min before the retention testing. Bilateral 6-OHDA lesions to NAS totally abolished, and to NSL did not affect, the positive effect of angiotensins on recall of information in a passive avoidance situation. Moreover, bilateral 6-OHDA lesions to NAS but not to NSL significantly attenuated the locomotor activity of rats in an open-field test. Nevertheless, it had no essential significance on the evaluation of the influence of the disruption of the dopaminergic endings in both structures on the facilitatory effect of angiotensins on retrieval process. These results suggest that the dopaminergic projection to NAS, but not to NSL is involved in the expression of the facilitatory effect of AII and AII(3–7) on memory motivated affectively evaluated in a passive avoidance situation.