Analysis of current noise evoked by nicotinic agonists in rat submandibular ganglion neurones.

The kinetics of the responses of rat submandibular ganglion neurones to nicotinic agonists were investigated by the analysis of agonist-induced membrane current noise. Two kinetic components are found in the responses of these cells to acetylcholine, carbachol, suberyldicholine, dimethyl-4-phenylpiperazinium and nicotine, in agreement with previous findings of two components in evoked synaptic currents in these cells. Small, though significant, differences in the relative amplitudes of the two kinetic components were observed in the spectra of noise evoked by the different agonists. In particular, the fast component in the response to carbachol was relatively larger with respect to the slow component than with any other agonist tested. No measurable dependence of the relative sizes of the two components on agonist concentration or membrane potential was observed. The evidence supports the hypothesis that the two kinetic components are the product of two independent channel populations for which the agonists tested show some slight differences in selectivity.