Carotid body thin slices: responses of glomus cells to hypoxia and K(+)-channel blockers.

We describe the rat carotid body thin slice preparation, which allows to perform patch-clamp recording of membrane ionic currents and to monitor catecholamine secretion by amperometry in single glomus cells under direct visual control. We observed several electrophysiologically distinct cell classes within the same glomerulus. A voltage- and Ca(2+)-dependent component of the whole cell K(+) current was reversibly inhibited by low P(O(2)) (20 mmHg). Exposure of the cells to hypoxia elicited the appearance of spike-like exocytotic events. This response to hypoxia was reversible and required extracellular Ca(2+) influx. Addition of tetraethylammonium (TEA, 2-5 mM) to the extracellular solution induced in most (>95%) cells tested a secretory response similar to that elicited by low P(O(2)). Cells non-responsive to hypoxia but activated by exposure to high external K(+) were also stimulated by TEA. A secretory response similar to that of hypoxia or TEA was also observed after treatment of the cells with iberiotoxin to block selectively maxi-K(+) channels. Our data further support the view that membrane ion channels are critically involved in sensory transduction in the carotid body. We demonstrate that in intact glomus cells inhibition of voltage-dependent K(+) channels can contribute to initiate the secretory response to low P(O(2)).