GLUTAMATE STIMULATES DOPAMINE RELEASE FROM CORTICAL AND LIMBIC RAT-BRAIN IN-VITRO

In vitro superfusion studies were performed to compare the glutamaterg ic control of dopamine release from minislices of rat striatum, olfact ory tubercle and frontal cortex. In the absence of Mg2+, release of en dogenous dopamine from olfactory tubercle and striatum, and [H-3]dopam ine from frontal cortex, was stimulated by glutamate (at concentration s of 0.3, 3 and 1 mM respectively). In all three areas the response to N-methyl-D-aspartate (NMDA) was greater than that to kainate, implyin g mediation largely by NMDA receptors, with non-NMDA receptors contrib uting to a smaller extent. This was confirmed by antagonist studies in the frontal cortex, where the response to glutamate was largely (70%) blocked by 2-amino-5-phosphonopentanoic acid (AP5), and further block ed by AP5 + 6,7-dinitroquinoxaline-2,3-dione (DNQX), In the olfactory tubercle and striatum, glutamate was as effective as NMDA, but in the frontal cortex the response to NMDA was significantly larger than that to glutamate.