The Ionic Mechanism Of Repetitive Firing In Rat DRG Neurons

Repetitive firing is a primary physiological phenomenon commonly seen in the functional activity of neurons. It plays an important encoding role in the information processing in the nervous system. The neuronal repetitive firing and its generating mechanism is more and more concerned but the reason and the ionic mechanism of such repetitive firing are not recognized completely and deepgoingly.In the present study, the generating mechanism and the function of sodium, potassium or calcium channels in repetitive firing are investigated using the voltage-clamp and current-clamp methods in patch-clamp technique in the freshly isolated neurons of rat dorsal ganglion(DRG).The main results are as follows:1. Repetitive firing can be induced by a sustained depolarizing stimulation in DRG neurons with frequency proportional to the intensity of depolarization. The frequency of repetitive firing increases from 5.26Hz to 100Hz while the membrane potential is depolarized from -40.7mV to -7.6mV, under the action of a depolarizing current increasing from 40pA to 840pA. In this period, the frequency of the repetitive firing is proportional to the depolarization of membrane potential, with an approximate ratio of 16.02Hz/10mV.2. The amplitude and frequency of repetitive firing are decreased by the reduction of temperature. Suggesting that the reduction of temperature decreases the ability of DRG neurons to generate repetitive firing.3. Repetitive firing is completely eliminated in Ca-free solution. The frequency of repetitive firing is altered by the change of extracellular calcium concention, and higher calcium concentration increases the frequency of repetitive firing.