THE NONCOMPETITIVE NMDA ANTAGONIST MK-801 INCREASES FOOD-INTAKE IN RATS

A role for excitatory amino acids in the control of feeding behavior h as not been extensively investigated. Nevertheless, there is direct an d circumstantial evidence to indicate that some circuits involved with feeding behavior include glutamatergic elements. To test the hypothes is that endogenous glutamate participates in the control of food intak e, we performed experiments to determine whether MK-801, a non-competi tive N-methyl-D-aspartate (NMDA) ion channel antagonist, is capable of altering intake of liquid and solid foods in hungry or satiated rats. Following a 16 h fast, intake of 15% sucrose was significantly enhanc ed by systemic treatment with MK-801. Water intake was not altered by the NMDA antagonist. Rats did not ingest more rat chow after MK-801, u nless they had been fasted. When a more palatable food (cookies) was o ffered, MK-801 did increase intake. Thus MK-801 enhanced food intake o nly when feeding was initiated by food-deprivation or increased palata bility. In conclusion, our results support the hypothesis that endogen ous glutamate plays a role in the control of food intake. Blockade of NMDA receptor function by MK-801 may diminish or delay satiety signals , rather than initiate feeding behavior per se. Copyright (C) 1997 Els evier Science Inc.