THE PARTICIPATION OF NITRIC-OXIDE IN THE FACILITATOR EFFECT OF ARGININE-VASOPRESSIN ON MEMORY

In this study we tested the hypothesis that nitric oxide (NO), which f unction as a novel type of inter-cellular messenger in the central ner vous system (CNS) participated in the facilitator effect of arginine v asopressin (AVP) on learning and memory. Recent investigations have pr ovided evidences that inhibition of NO synthesis attenuated the vasodi latation caused by AVP, and inhibited the improvement of learning and memory evoked by angiotensin II, AVP as well as pharmacologically prod uced increase in endogenous NO facilitates the consolidation of shock avoidance learning. We evaluated the behavioural effects of AVP at dos e 1 mu g after the inhibition of NOS by N-G-nitro-L-arginine methyl es ter (L-NAME) at dose 10 mu g, and after the injection of endogenous do nor of NO-L-argnine-10 mu g in the retrieval of passive avoidance situ ation, and in consolidation of active avoidance responses. The locomot or activity of all investigated drugs was tested in the open field tes t. AVP facilitated the recall of passive avoidance responses and conso lidation of active avoidance responses. Neither the increase of NO con centration after the injection of L-arginine nor the decrease of NO af ter the inhibition of NOS by L-NAME changed the behavioural effects of AVP. L-arginine increased the psychomotor behaviour and L-NAME decrea sed the activity of animals in the ''open field'' test. L-arginine its elf improved the consolidation of active avoidance responses. Our resu lts indicate that central action of AVP is probably independent of NO concentration in the brain.