THE RESPONSES OF THE SUPERIOR CERVICAL GANGLION TO SINGLE AND REPETITIVE ACTIVATION

Abstract

The electric responses of the sup. cervical ganglion and the postganglionic fibers to preganglionic nerve volleys were studied in cats. Single shocks, 2 shocks at variable intervals and repetitive stimulation at various frequencies were used. At least 4 groups of elements may be recognized in the ganglion, distinguished by their latency and by the threshold of the preganglionic fibers which activate them. The slowest group U appears sometimes with stimuli which fail to excite the faster group M3. The ganglionic spike potentials are succeeded first by a negative and later by a positive after-potential. These after-potentials sum during repetitive stimulation at adequate frequencies. Growth or decrease of the magnitude of the spikes which occurs in different conditions is not related to the after-potentials. Increase or decrease of latency, particularly striking during tetanic stimulation and immediately after, is independent of the after-potentials and of the changes of magnitude of the spikes. Repetitive discharges of ganglion cells to single preganglionic volleys may occur during tetanic stimulation or during the post-tetanic period. The bearing of the data on theories of synaptic transmission is discussed.