Stimulation of Sensory Somatic Nerves in Relation to the Viscero-Pannicular Reflex. ∗

Abstract

It has been demonstrated that the viscero-pannicular reflex (Ashkenaz and Spiegel 1 ) is an objective, observable, constant criterion of the intactness of certain centripetal visceral pathways from the gall bladder of the cat. This reflex, which consists of a contraction of the panniculus carnosus muscle of the cat following adequate stimulation (distention) of a hollow viscus, such as the gall bladder, has been utilized in an analysis of centripetal conduction from the abdominal viscera of the cat (Ashkenaz 2 ). Since this reflex is associated with the type of visceral stimulation (distention of a hollow viscus and stretching of smooth muscle) which ordinarily results in the sensation of pain in man, it has seemed interesting to determine whether stimulation of sensory nerves, other than visceral, known to conduct pain sensation, would also evoke a pannicular response.

The sciatic and phrenic nerves of decerebrate cats and cats under ether and dial anesthesia were stimulated by faradic stimuli from an inductorium as well as by repetitive stimulation with a thyratron stimulator but no indication of a contraction of the panniculus carnosus muscle was observed during such stimulation. If, during stimulation of the phrenic nerve, the splanchnic nerve were stimulated mechanically or the gall bladder were stretched or pulled, a contraction of the panniculus carnosus was observed, and this contraction ceased immediately upon cessation of the splanchnic or gall bladder stimulation, even though the phrenic stimulation were continued.

From these observations, it seems that a pannicular response is not usually and easily elicited by painful stimulation of afferent somatic nerves far removed from the segmental region supplying the panniculus carnosus.

Summary. Stimulation of the sciatic and phrenic nerves in decerebrate cats and in cats under ether and dial anesthesia by faradic stimulation with an inductorium or repetitive stimulation with a thyratron stimulator does not elicit a contraction of the panniculus carnosus muscle, but simultaneous or independent stimulation of the gall bladder or the splanchnic nerve (right) does evoke a contraction of the panniculus carnosus muscle.