CHARACTERISTICS OF ACTION-POTENTIALS RECORDED FROM CAT SPINAL GANGLION NEURONS INVIVO

Action potentials were recorded intracellularly from L4-S1 dorsal root ganglion (DRG) neurons of anesthetized cats. Based on the shape of th eir waveforms the action potentials were classified as either typical (n = 49) or atypical (n = 8). The atypical potentials were characteriz ed by a slowly rising, well-defined early depolarization of small ampl itude and long duration. This kind of prepotential randomly triggered spike potentials with varying latencies. The average rise time, durati on, and area of atypical potentials were significantly different than those of typical ones. In some DRG neurons, the afterhyperpolarization was preceded by a delayed repolarization, or was followed by postspik es and long-lasting afteroscillations. In others, small depolarization s could be recorded during subthreshold stimulation. These depolarizat ions arose slightly later than the spike potential, and were all or no ne, with relatively stable onset latency and size. These results are e xplained by postulating the presence of chemical synapses and/or elect rotonic coupling in the DRG.