DYNORPHIN USES A NONOPIOID MECHANISM TO POTENTIATE N-METHYL-D-ASPARTATE CURRENTS IN SINGLE-RAT PERIAQUEDUCTAL GRAY NEURONS

The interaction of the endogenous K-opioid, dynorphin, with N-methyl-D -aspartate (NMDA) receptors was studied in single periaqueductal gray (PAG) cells using the whole cell patch recording technique. We have fo und that dynorphin A (1-17) rapidly and reversibly potentiates NMDA-ac tivated currents in a subpopulation of FAG cells. The potentiation can not be blocked by the non-specific opioid antagonist, naloxone, nor ca n it be reversed by the specific kappa-opioid antagonist, nor-BNI. In addition, the nonopioid fragment of dynorphin, dynorphin A (2-17), is effective in potentiating NMDA currents, while the specific kappa-opio id, U50,488, cannot mimic the action of dynorphin A (1-17). The non-op ioid dynorphin action and the rapid onset and recovery of the potentia tion are consistent with the idea that dynorphin interacts directly wi th NMDA receptors in FAG cells. (C) 1998 Published by Elsevier Science Ireland Ltd.