ADRENERGIC NEURONS IN THE CAT SUPERIOR CERVICAL GANGLION AND CERVICAL SYMPATHETIC NERVE TRUNK. A HISTOCHEMICAL STUDY

¹ Department of Pharmacology, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania

The superior cervical ganglion and cervical sympathetic nerve trunk of the cat were studied for catecholamine-containing neurons by a histochemical fluorescence method. This ganglion contains an extensive system of adrenergic nerve terminals in close anatomic proximity to the cell bodies. Pre- and/or postganglionic nerve section (3 days) resulted in a marked increase in the number and intensity of fluorescence of the catecholamine-containing nerve fibers within the ganglion. In addition there is an increased catecholamine fluorescence within the sympathetic cell bodies. It is suggested that this intraganglionic system of adrenergic terminals are axon collaterals from postganglionic processes that "feedback" upon the ganglion cells and possibly on presynaptic elements. A population of sympathetic cells at the caudal end of the ganglion was uncovered whose postganglionic axons were contained within the cervical sympathetic nerve trunk. The cervical sympathetic trunk also contains numerous sympathetic ganglion cells in addition to adrenergic nerve fibers. It is suggested that the sympathetic neurotransmitter may serve to influence (modulate) transmission through the ganglion.