Excision-activated chloride channels in cultured postnatal rat hippocampal neurons

Chloride permeable intermediate conductance single channel events activated on patch excision were found in outside-out patches from cultured postnatal hippocampal neurons. A majority of the channels had a conductance of 83 +/- 2.1 pS when recorded in a symmetrical TEACl solution. Two other populations of channels with conductance values of 62 +/- 2.1 pS and 145 +/- 1.9 pS were also observed. The reversal potentials for these intermediate conductance Cl- channels coincided with that of the GABA activated channels. The channels characteristically appeared 5-15 min after patch excision, suggesting that these channels may be blocked by some diffusible factors under physiological conditions. Based on the measurements of channel burst durations while the channel was partially blocked, and the channel open times after complete relief from the block, the mechanism of blockade does not appear to be a simple open channel blockade. The high prevalence and its potential regulation by cytosolic factors suggest an important physiological role for these Cl- channels coupling neuronal excitability with cellular metabolism.