K+-current modulated by PO2 in type I cells in rat carotid body is not a chemosensor

According to the membrane channel hypothesis of carotid body O-2 chemoreception, hypoxia suppresses K+ currents leading to cell depolarization, [Ca2+](i) rise, neurosecretion, increased neural discharge from the carotid body. We show here that tetraethylammonium (TEA) plus 4-aminopyridine (4-AP) which suppressed the Ca2+ sensitive and other K+ currents in rat carotid body type I cells, with and without low [Ca2+](o) plus high [Mg2+](o), did not essentially influence low P-O2 effects on [Ca2+](i) and chemosensory discharge. Thus, hypoxia may suppress the K+ currents in glomus cells but K+ current suppression of itself does not lead to chemosensory excitation. Therefore, the hypothesis that K+-O-2 current is linked to events in chemoreception is not substantiated. K+-O-2 current is an epiphemenon which is not directly linked with O-2 chemoreception. (C) 1998 Elsevier Science B.V. All rights reserved.