Properties of Proton-Gated Ion Channels in Sensory Neurons of Rats

Abstract

In experiments on the somata of sensory neurons isolated from the spinal and trigeminal ganglia of rats, we characterized three subclasses of proton-gated currents differing from each other in their kinetics of desensitization and characteristics of stationary desensitization (but not in the characteristics of stationary activation). A voltage clamp technique in the whole cell configuration and intracellular perfusion were used. Expression of the channels providing currents of each subclass depended on the soma diameter but not on anatomical localization of the neuron. Proton-gated channels of type I were characterized by mono- or biexponential kinetics of current desensitization with the duration of complete decay within a 1 to 15 sec range; the mean pH50 of the curve of stationary desensitization was 7.21 ± 0.02. Channels of type II possessed mostly monoexponential desensitization kinetics with the duration of decay within a 1 to 3 sec range; their pH50 of the stationary desensitization curve was 7.11 ± 0.02. Channels of type III showed mostly biexponential desensitization kinetics; the complete current decay lasted about 5 sec, while the mean pH50 was about 6.78 ± 0.02. Channels of type I were typical of small neurons (soma diameter 10-20 μm), while those of types II and III were found mostly in large cells (35-60 μm).