Somatic afferent regulation of plasma immunoreactive glucagon in anesthetized rats

We examined the neural mechanisms of the effect of noxious and innocuous mechanical stimulation of various segmental skin areas on the plasma glucagon concentration. Experiments were performed using chloralose- and urethane-anesthetized rats, ventilated artificially. The cutaneous stimuli of two different modalities, noxious and innocuous mechanical stimuli by pinching and brushing, were delivered to various segmental areas including the face, forelimb for forepaw, abdomen, and hindlimb or hindpaw. Blood samples were collected from the femoral artery, and plasma glucagon was measured by radioimmunoassay. Cutaneous pinching for 3.5 min of the face, forepaw, abdomen, or hindpaw increased the plasma immunoreactive glucagon (IRG), and the increase was larger following pinching of the abdmen or hindpaw than pinching of the face or forepaw. Brushing for 3.5 min of the face, forelimb, abdomen, or hindlimb did not significantly affect the plasma IRG. The increase in plasma IRG following skin pinching was abolished when both parasympathetic vagal 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. These findings indicate that excitation of cutaneous nociceptive afferent information from the various spinal segments can regulate glucagon secretion from the pancreas as a reflex response, whose efferent limb is dually composed of both sympathetic and parasympathetic nerves.