Ca-dependent regulation of the Na-K-pump by post-tetanic sensitization of extrasynaptic cholinoreceptors in common snail neurons.

Studies were conducted on the role of the Na,K pump and intracellular calcium in the previously observed phenomenon of increased cholinosensitivity of the somatic membranes of neurons LPa3 and RPa3 in the common snail, induced by electrical tetanic stimulation (10.5 mA. 0.1 sec, 2 impulses/sec; 2 min) of the afferent input (the intestinal nerve). Recordings were made of integral transmembrane acetylcholine-evoked currents by two-electrode membrane voltage clamping. After intracellular administration of the Na,K pump inhibitor ouabain (70 microM), there was no post-tetanic increase in neuron cholinosensitivity. Intracellular injection of the calcium ion chelator BAPTA suppressed the sensitization of somatic cholinoreceptors after orthodromal tetanization. It was concluded that the Na,K pump is involved in the mechanism of post-tetanic potentiation of cholinosensitivity in the bodies of defensive behavior command neurons in the common snail, this involvement being Ca-dependent.