THE EFFECTS OF N-METHYL-D-ASPARTATE (NMDA) AND NON-NMDA RECEPTOR AGONISTS AND ANTAGONISTS ON HYPOTHALAMIC NEURONS IN THE ANESTHETIZED RAT WHICH RESPOND TO CHANGES IN SCROTAL SKIN TEMPERATURE

There are neurones in the pre-optic anterior hypothalamus of the anaes thetised rat which respond to changes in scrotal skin temperature. Neu ronal firing rate can be increased by raising the scrotal skin tempera ture above 36 degrees C, and also by ionophoretic application of eithe r N-methyl-D-aspartate (NMDA) or alpha-amino-3-hydroxy-5-methyl-4-isox azole propionic acid (AMPA) (a non-NMDA receptor agonist). The increas e in neuronal firing evoked by thermal stimulation was prevented or di minished by concurrent application of either D-2-amino-5-phosphonopent anoic acid (D-AP5) (an NMDA receptor antagonist) or -dihydroxy-6-nitro -7-sulfamoyl-benzo(F)quinoxaline (a non-NMDA receptor antagonist) at d oses which were sufficient to abolish or significantly diminish the ef fect of the specific agonist. It is probable that both NMDA and non-NM DA receptors are involved in the scrotal thermoafferent pathway in the rat.