FURTHER EVIDENCE FOR THE INVOLVEMENT OF A HIPPOCAMPAL CGMP CGMP-DEPENDENT PROTEIN-KINASE CASCADE IN MEMORY CONSOLIDATION/

HIPPOCAMPAL cyclic GMP (cGMP) has been recently postulated to particip ate in an early phase of memory consolidation of an inhibitory avoidan ce learning in rats. Here we report on the effects of the intrahippoca mpal infusion of a soluble guanylyl cyclase inhibitor (LY 83583) in th e consolidation of one-trial step-down inhibitory avoidance and on the effect of this task on hippocampal cGMP levels and cGMP-dependent pro tein kinase (PKG) activity. Bilateral intrahippocampal administration of LY 83583 (2.5 mu g per side) caused full amnesia for inhibitory avo idance when given immediately (0 min) after training, but not 30 min p ost-training. Rats submitted to the inhibitory avoidance task showed a significant increase in both cGMP levels and in PKG activity in the h ippocampus at 0 min after training. No changes were observed 30 min af ter training. These findings provide further evidence that the hippoca mpal cGMP/PKG cascade is involved in the early stages of memory format ion of an inhibitory avoidance task in rats.