Axonal conduction velocity and input conductance in petrosal ganglion primary sensory neurones of the cat.

Petrosal ganglion chemoreceptor neurones were impaled with glass microelectrodes in an 'in vitro' preparation maintained at 36.5 degrees C. For each cell, the input conductance and the axonal conduction velocity were calculated from the voltage change produced by a hyperpolarizing pulse, and from the latency of the spike evoked by carotid nerve stimulation. In 34 neurones, the average values for these variables were 3.7 X 10(-8) Siemens and 10 m/s. The two parameters were related by a power function with an exponent of 0.9, which is lower than the value of 2 expected on the basis of simple linear relations between soma and axon diameters and between axon diameter and conduction velocity.