Electrophysiological evidence for N-methyl-D-aspartate excitatory amino acid receptors in the rat supraoptic nucleus in vitro.

The responses of neurons in slices of the rat supraoptic nucleus (SON) to afferent stimulation were recorded under current-clamp conditions. In magnesium (Mg2+)-free incubation medium, synaptic responses were prolonged and were partially antagonized by the non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist (+)-5-methyl-10,11-dihydro-5H- dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate (MK-801). During blockade of non-NMDA excitatory amino acid (EAA) receptors, the synaptic responses in Mg(2+)-free medium were blocked by the competitive NMDA receptor antagonist 2-amino-5-phosphonopentanoic acid (AP5). The results of these experiments provide electrophysiological evidence for the existence of NMDA receptors in the rat SON.