The 5-HT 1A receptor and recognition memory : Possible modulation of its behavioral effects by the nitrergic system

Abstract

Functional activation of the 5-HT 1A receptor inhibits cognition, although discrepant findings have also been reported. The present study was designed to investigate the role of the 5-HT 1A receptor on recognition memory in the rat. For this purpose, the effects induced by the 5-HT 1A agonist R-(+)-8-hydroxy-2-(di- n-propylamino)tetralin hydrobromide (8-OH-DPAT) and the 5-HT 1A antagonist WAY 100635 on memory were evaluated by using the object recognition task. In addition, the possible involvement of the nitrergic system on 5-HT 1A receptor's effects was also assessed by using the same behavioral procedure. In the first dose–response study, post-training administration of 8-OH-DPAT (0.1 and 0.3 mg/kg, subcutaneously (s.c.)) dose-dependently impaired animals’ performance in this test. WAY 100635 (0.3 and 1 mg/kg, intraperitoneally (i.p.)) successfully antagonized these 8-OH-DPAT-induced performance deficits. The NO donor molsidomine (2 and 4 mg/kg, i.p.) counteracted cognition deficits produced by the highest dose of 8-OH-DPAT (0.3 mg/kg). Our findings indicate (a) that the 5-HT 1A receptor is involved in recognition memory, and (b) that a NO component modulates the effects of the 5-HT 1A receptor on learning and memory.