Stimulation-induced changes in the intracellular sodium activity of the crayfish stretch receptor.

Changes in intracellular Na+ activity (aiNa) caused by mechanical stimulation in the slowly adapting stretch receptor of the crayfish were examined using Na+-selective microelectrodes. A series of brief stretches (each giving rise to a brief receptor potential and a single action potential) induced a reversible increase in aiNa which was proportional to the stimulation frequency in the range examined, 0-9.5 Hz. At 9.5 Hz, aiNa increased by 4-5 mM from the resting value of 7-10 mM. Tetrodotoxin (TTX) reduced, but did not abolish the stimulation-dependent increase in aiNa indicating the involvement of a Na+-influx pathway in addition to the potential-dependent, TTX-sensitive sodium channels of the neuronal plasma membrane. A likely candidate for this TTX-resistant pathway are the cationic transducer channels of the dendrites.