A patch-clamp analysis of membrane currents in salamander olfactory receptor cells

Abstract

Isolated olfactory receptor cells were obtained from salamander olfactory epithelium and kept in short term culture conditions. They were studied by means of the whole cell patch-clamp technique associated with ionic substitutions and channel blockers. Under physiological ionic gradients, these cells had a resting potential of -39 +/- 10 mV and an input resistance above 2 G omega. Using different channel blockers and ion substitutions, we could separate several distinct components in the overall whole cell current. In most cells, inward current reflected the activation of a TTX resistant conductance which was blocked by cobalt ions. This inward current lasted only for about 5 min of whole cell recording. In a minority of cells, a TTX sensitive sodium current was also observed. The outward K+ current was blocked when the cells were loaded with cesium and tetraethylammonium. It inactivated slowly and incompletely and could act as a depolarization limited in case of intense odour stimulations. Single channel analysis from outside out patches suggested that it corresponded to the activity of 34 pS channels. In some cells a rapidly inactivating K+ current was also present. Single channel activities (27 +/- 6 pS) were commonly recorded with KCl-filled pipettes, at resting or hyperpolarized membrane potentials but not at depolarized potentials. Membrane hyperpolarization increased the open-state probability. A preliminary study with odorant stimulations indicated the existence of a stimulus-induced current probably corresponding to the activation of the chemoreceptive membrane.