THE SILENT PERIOD OF SYMPATHETIC PREGANGLIONIC NEURONS

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Abstract
The behavior of single sympathetic preganglionic neurons, during and after repetitive antidromic driving, was studied with extracellular microelectrodes in the cat's spinal cord. It was found that repetitive antidromic excitation of spontaneously active units could produce a subsequent, long-lasting inactivity or "silent period". A similar silent period could be produced by antidromic excitation of units in the acutely isolated and deafferentated, upper thoracic, spinal cord. It occurred whenever the neuron soma had been involved in high-frequency activity. It is concluded that the silent period of sympathetic preganglionic neurons is generated in the spinal cord and is due to accumulation of post-activation depression by the cell bodies of the affected units.