Discharge patterns of sympathetic neurons supplying skeletal muscle and skin in man and cat.

Skeletal muscle and skin of humans and cats are supplied by various sympathetic systems: vasoconstrictor neurons, sudomotor neurons, vasodilator neurons and pilomotor neurons. Only vasoconstrictor and sudomotor neurons have resting activity in both species. Discharge patterns of spontaneous activity in postganglionic neurons with resting activity as well as their reflex responses to various stimuli have been compared for both species: (1) muscle vasoconstrictor neurons react similarly in both species; they are under dominant control of arterial baroreceptors; (2) in both species cutaneous vasoconstrictor neurons are under no or weak control of arterial baroreceptors and they are influenced in similar ways by thermal stimuli. In contrast, other (somatic and visceral) stimuli elicit largely inhibition in these neurons in cats but excitation in humans. This may be due to the different experimental situations (anesthesia, etc.); (3) sudomotor neurons in humans are involved in thermoregulation, in cats they are not. The differences in the reflexes may also be due to the different experimental situations and to species differences; (4) the implications of studies on sympathetic neurons in humans and animals for the progress of research in this field have been discussed.