ANALYSIS OF L-[H-3]-GLUTAMATE RADIOLIGAND BINDING TO PLASMA-MEMBRANESOF THE AMPULLAE OF LORENZINI OF SKATES

RADIOLIGAND binding analysis of L-[H-3]-glutamate to plasma membranes of the ampullae of Lorenzini in the skate revealed one type of binding site with K(D) = 286 nM and B(max) = 2.1 pmol mg-1 protein. It was re vealed that Na+, K+, Ca2+ and Mg2+ inhibited the L-[H-3]-glutamate bin ding, while Cl- had no effect. The glutamate agonists kainate, quisqua late and N-methyl-D-aspartate (NMDA) were shown to inhibit glutamate b inding in a dose-dependent manner. The results obtained confirm the el ectrophysiological observations suggesting the existence of three type s of glutamate receptor at afferent synapses of the ampullae of Lorenz ini of skates.