D-CYCLOSERINE, A POSITIVE MODULATOR OF THE NMDA RECEPTOR, ENHANCES ACQUISITION OF A CONDITIONED TASTE-AVERSION

Pharmacological manipulations using agents that affect the action of t he N-methyl-D-aspartate (NMDA) receptor have been demonstrated to modu late acquisition and retention in experimental animals. Although it is well established that antagonists of this receptor debilitate acquisi tion of many experimental tasks, the effects of agonists of the recept or site have not been thoroughly examined, except for those of D-cyclo serine (DCS), a partial agonist of the NMDA receptor. In the present s tudy, DCS is demonstrated to enhance acquisition of a conditioned tast e aversion (CTA) in rats, extending the findings of facilitation of le arning with this agonist to a CTA paradigm. DCS itself did not cause a taste aversion nor did it summate with lithium chloride, the uncondit ioned stimulus? to increase avoidance of the conditioned stimulus in e xperimental animals. It appears that modulation of the NMDA receptor c an affect gustatory learning.