BLOCK OF RECEPTOR RESPONSE IN THE STRETCH-RECEPTOR NEURON OF THE CRAYFISH BY GADOLINIUM

The trivalent lanthanide gadolinium was found to block the mechanotransducer response in the stretch receptor neuron of the crayfish. At normal calcium concentration (13.5 mM) a 50 per cent block of the receptor current was found at 395 +/- 59 (mean +/- SD) mu-M gadolinium. At a calcium concentration of 1.35 mM a 50 per cent block of the receptor current was obtained at 103 +/- 14 (mean +/- SD) mu-M gadolinium. The potential activated potassium current was also affected by gadolinium. At 200 mu-M the amplitude of the peak outward current as a result of a 90 mV positive potential step was decreased by about 40 per cent. The fast inward sodium current was decreased less than 10 per cent by gadolinium. It is concluded that in the crayfish stretch receptor gadolinium blocks the receptor current, reflecting block of stretch-activated channels, but at higher concentrations than have been described for other stretch-activated channels. In addition the outward rectifier potassium current is also blocked reflecting a block of potassium channels.