Interaction between separate groups of preganglionic fibers in superior cervical sympathetic ganglia

Skok, V.I.; Myrhorods'kyl, V.M.

Fiziol Zh akad Nauk Ukr Rsr 13(6): 732-738


Accession: 024881550

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Action potentials were recorded from postganglionic fibers of the cat superior cervical ganglion (in situ), that arose in response to single stimulation of separate groups of preganglionic fibers in the cervical sympathetic nerve. If these single stimuli were produced simultaneously with a tetanic stimulation of neighboring groups of preganlionic fibers, an increase or decrease in the amplitude of single action potentials was observed. Tetanic stimulation in itself did not produce any noticeable action potentials in postganglionic fibers for its frequency (75 imp/sec.) was too high to produce synchronous discharges of ganglion cells. Among the cervical sympathetic nerve fibers there was no morphologically separate group which when stimulated frequently would cause total inhibition of synaptic transmission in the ganglion. At such stimulation a facilitation is usually observed, at least in synaptic transmission of the spike S2; even if the inhibition is observed for one of the spikes of complex action potential of postganglionic fibers the parallel facilitation is seen for other spikes. Among the fibers of cervical sympathetic nerve which have a high threshold some cause facilitation in the ganglion as well as those that cause the inhibition. Whether this inhibition is primary or secondary one, i. e., whether it is caused by special inhibitory fibers or the result of decreased excitability after stimulating those neurons where both groups of preganglionic fibers converge is unknown.