NMDA INDUCED GLUTAMATE RELEASE FRONT THE SUPRACHIASMATIC NUCLEUS - ANIN-VITRO STUDY IN THE RAT

The suprachiasmatic nucleus (SCN) has been identified as a pacemaker f or mammalian circadian rhythms. Excitatory amino acid receptors, espec ially N-methyl-D-aspartate (NMDA) receptors, have been considered to p lay an important role in the transmission of light information from th e retina to the circadian clocks in the SCN. In the present study, we showed that application of NMDA at circadian time (CT) 12-15 induced s ignificant glutamate release from the SCN region in vitro. The NMDA-in duced glutamate release was blocked by co-application of the NMDA rece ptor antagonist MK-801, but not by that of tetrodotoxin. These results suggested that glutamate stimulated its own release by activating NMD A receptors. This NMDA-induced glutamate release through NMDA receptor -mediated mechanisms might be involved in NMDA-induced potent phase sh ifts. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.