Metabotropic Glutamate Receptors Effects on Feeding
Every living organism has two biological driving forces: the need to reproduce and the need to feed. The need to feed is not merely a balancing act between energy expended and caloric intake. Ingestion of calorically sufficient and palatable foods is mediated by the central nervous system and its subsidiaries. The hypothalamus is the main mediator of homeostasis and the lateral hypothalamus (LH) is of particular interest in regards to feeding. Glutamate (Glu) is present throughout the mammalian brain and within the LH Glu influences feeding. Previously ionotropic glutamate receptors were shown to facilitate this response. Here, we have attempted to identify and demonstrate that metabotropic glutamate receptors (mGluRs) also influence feeding. Intracranial injections of drugs either activating or blocking mGluRs increases or suppresses food intake. These effects were limited to the LH, effects seen in different brain regions can be attributed to the diffusion of the agonist to the LH. Although blockage of mGluRs during a time period of high extracelluar glutamate concentration is ineffective in suppressing feeding, we discuss possible alternative mechanisms for these observations. None the less our findings suggest that group I mGluRs are involved in feeding.