SOMATIC AFFERENT REGULATION OF PLASMA-IMMUNOREACTIVE GLUCAGON IN ANESTHETIZED RATS

We examined the neural mechanisms of the effect of noxious and innocuo us mechanical stimulation of various segmental skin areas on the plasm a glucagon concentration. Experiments were performed using chloralose- and urethane-anesthetized rats, ventilated artificially. The cutaneou s stimuli of two different modalities, noxious and innocuous mechanica l stimuli by pinching and brushing, were delivered to various segmenta l areas including the face, forelimb or forepaw, abdomen, and hindlimb , or hindpaw. Blood samples were collected froth the femoral artery, a nd plasma glucagon was measured by radioimmunoassay. Cutaneous pinchin g for 3.5 min of the face, forepaw, abdomen, or hindpaw increased the plasma immunoreactive glucagon (IRG), and the increase was larger foll owing pinching of the abdmen or hindpaw than pinching of the face or f orepaw. Brushing for 3.5 min of the face, forelimb, abdomen, or hindli mb did not significantly affect the plasma IRG. The increase in plasma IRG following skin pinching was abolished when both parasympathetic v agal and sympathetic nerves to the pancreas were bilaterally severed. The increase in plasma IRG was not abolished after bilateral severance of either the parasympathetic vagal or sympathetic nerves alone. Thes e findings indicate that excitation of cutaneous nociceptive afferent information from the various spinal segments can regulate glucagon sec retion from the pancreas as a reflex response, whose efferent limb is dually composed of both sympathetic and parasympathetic nerves.