The reversal potential of Ca2+-activated Cl- currents indicates that chick sensory neurons accumulate intracellular Cl-

In order to establish the physiological role of the Ca2+-activated Cl- current (I-Cl(Ca)) of chick primary afferent neurons, I measured the reversal potential of this current using either the amphotericin perforated patch technique (that alters intracellular Cl-) or the gramicidin perforated patch technique (that does not perturb intracellular Cl-). In the amphotericin experiments at 35 degreesC, I-Cl(Ca) reversed at the Cl- equilibrium potential (E-Cl = -24 mV) set by the superfusate (147 mM Cl-) and the pipette solution (60 mM Cl-). In contrast, in the gramicidin experiments at 35 degreesC, I-Cl(Ca) reversed at -42 +/- 2 mV, midway between E-Cl of the solutions and E-Cl expected if Cl- were passively distributed. Thus the gramicidin perforated patch technique monitors Cl- currents without perturbing intracellular Cl-. Further, the data imply that chick dorsal root ganglia (DRG) neurons actively accumulate Cl-. I-Cl(Ca) reversed at the same potential (-46 +/- 3 mV) at 20 degreesC indicating that the non-equilibrium distribution of Cl- is maintained at the lower temperature. Thus, I-Cl(Ca) is a depolarizing current that can contribute to the after-depolarization in chick DRG neurons and thereby alter Ca2+ influx. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.