RECORDING OF A LARGE-CONDUCTANCE CHLORIDE CHANNEL IN NORMAL RAT LACTOTROPHS

Membrane current fluctuations resembling channel openings and closings were observed in the whole cell configuration of the patch-clamp tech nique in normal rat lactotrophs in primary culture. Using high-gain he ad stage in whole cell configuration, we characterized the nature and pharmacological properties of the ionic channel underlying these fluct uations. This channel, found in small numbers (<10 per cell), was spec ific for Cl- because its reversal potential varied with Cl- gradients, according to the Nernst equation, and its unitary amplitude was linea rly related to membrane potential from -100 to 0 mV. Slope conductance was close to 100 pS. Analyzing open times, we demonstrated its Ca2+ a nd potential dependence. Four sublevels were observed. Sire suggest th at this channel, belonging to the background Cl- channel group, takes part in the regulation of intracellular Cl- concentration of normal ra t lactotrophs.