Osmosensitivity of an inwardly rectifying chloride current revealed by whole-cell and perforated-patch recordings in cultured rat cortical astrocytes

The osmosensitivity of the inwardly rectifying Cl- current (I-Clh), express ed by primary cultured rat neocortical astrocytes long-term treated with di butyryl cyclic AMP, was investigated in the whole-cell and perforated-patch modes. In whole-cell experiments, whereas hypotonic extracellular solution (Delta = 100 mOsmol) did not cause any change in I-Clh, hypertonicity prod uced a slowly developing, similar to 40% reversible decrease in current mag nitude, By contrast, in perforated-patch experiments, exposure to a less hy pertonic saline (Delta = 50 mOsmol) depressed the current to similar to 50% , and hypotonicity induced a similar to 50% slow increase in I-Clh. These d ifferences in osmosensitivity between the two experimental modes suggest th at the osmoregulation of I-Clh may be mediated by complex intracellular mec hanism(s), which appear(s) to be partly compromised by the dialysis of the astrocytic cytoplasm, (C) 2001 Federation of European Biochemical Societies . Published by Elsevier Science B.V. All rights reserved.