The GABA B receptor and recognition memory: possible modulation of its behavioral effects by the nitrergic system

Abstract

Functional activation of the GABA B receptor inhibits learning and memory processes, though discrepant findings, in this context, have also been reported. The present study was designed to investigate the role of the GABA B receptor on recognition memory in the rat. For this purpose, the effects induced by the GABA B agonist baclofen and the GABA B antagonist p-(3-aminopropyl)- p-diethoxymethylphosphinic acid (CGP 35348) on memory were assessed by using the object-recognition task. In addition, the possible involvement of the nitrergic system on GABA B receptor’s effects was also evaluated by using the same behavioral procedure. This is a working-memory paradigm based on the differential exploration of a new and familiar object. In a first dose-response study, baclofen (0.5, 2, and 4 mg/kg, i.p.), dose-dependently impaired animals’ performance in this task, suggesting a modulation of acquisition and storage of information. CGP 35348 (100 and 300 mg/kg, i.p.), counteracted these baclofen-induced performance deficits. The nitric oxide donor molsidomine, at the dose of 4 but not 2 mg/kg, i.p, successfully antagonized the deficits on cognition induced by the highest dose of baclofen (4 mg/kg). These results indicate a) that the GABA B receptor is involved in recognition memory and b) that an NO component modulates the effects of the GABA B receptor on learning and memory.