Lateral hypothalamic NMDA receptor subunits NR2A and/or NR2B mediate eating: immunochemical/behavioral evidence

Cells within the lateral hypothalamic area (LHA) are important in eating co ntrol. Glutamate or its analogs, kainic acid (KA) and N-methyl-D-aspartate (NMDA), elicit intense eating when microinjected there, and, conversely, LH A-administered NMDA receptor antagonists suppress deprivation- and NMDA-eli cited eating. The subunit composition of LHA NMDA receptors (NMDA-Rs) media ting feeding, however, has not yet been determined. Identifying this is imp ortant, because distinct second messengers/modulators may be activated by N MDA-Rs with differing compositions. To begin to address this, we detected L HA NR2A and NR2B subunits by immunoblotting and NR2B subunits by immunohist ochemistry using subunit-specific antibodies. To help determine whether NMD A-Rs mediating feeding might contain these subunits, we conducted behaviora l studies using LHA-administered ifenprodil, an antagonist selective for NR 2A- and/or NR2B-containing NMDA-Rs at the doses are used (0.001-100 nmol). Ifenprodil maximally suppressed NMDA- and deprivation-elicited feeding by 6 3 and 39%, respectively, but failed to suppress KA-elicited eating, suggest ing its actions were behaviorally specific. Collectively, these results sug gest that LHA NMDA-Rs, some of which contribute to feeding control, are com posed of NR2A and/or NR2B subunits, and implicate NR2A- and/or NR2B-linked signal transduction in feeding behavior.