FEEDING INDUCED BY BLOCKADE OF AMPA AND KAINATE RECEPTORS WITHIN THE VENTRAL STRIATUM - A MICROINFUSION MAPPING STUDY

The corticostriatal pathway is believed to utilize the excitatory amin o acid glutamate as its transmitter, and the striatum contains high le vels of all glutamate receptor subtypes. It has recently been demonstr ated that blockade of lpha-amino-3-hydroxy-5-methylisoxazole-4-propion ic acid (AMPA) and kainate glutamate receptors in the medial part of t he accumbens, corresponding to the medial shell subregion, results in a pronounced feeding response. In order to more precisely localize thi s response, a microinfusion mapping study was conducted. Bilateral mic roinfusions of 6,7-dinitroquinoxaline-2,3-dione (DNQX, 0, 50, 250, 750 ng/0.5 mu l), an antagonist that blocks AMPA and kainate receptors, w ere carried out in eight striatal subregions in different groups of an imals. In non-deprived rats, food intake (normal chow), feeding durati on, and several other behavioral measures were assessed during a 30 mi n test session. DNQX significantly and potently enhanced food intake w hen injected into the accumbens shell, but not into any other region e xamined, including accumbens core, anterior dorsal, posterior dorsal, ventromedial, dorsomedial, and ventrolateral striatum. The most sensit ive site within the accumbens was found to be the posterior aspects of the shell, in which the lowest dose (50 ng DNQX) augmented feeding. T hese results suggest that a circumscribed region within the nucleus ac cumbens has a unique role in the control of feeding. It is postulated that removal of tonic excitatory inputs to this region with DNQX resul ts in disinhibition of brain circuits critical for ingestive behavior. (C) 1997 Elsevier Science B.V.