Abstract
Recent our histochemical study has shown that the sensory nerves travel in both the sympathetic and parasympathetic nerve routes supplying to the submandibular gland in the rat. In the present study we analyze afferent neural activities in the peripheral cut ends of the sympathetic and parasympathetic nerve branches innervating the submandibular gland in urethane-anesthetized rats. The following results were obtained: 1) The afferent activity could be recorded from both sympathetic and parasympathetic routes; 2) both afferents had no spontaneous activities, but responded to mechanical pressure applied onto the gland; 3) when back pressure was applied from the main excretory duct by infusion of saline, both afferents showed tonic impulse discharges at pressure of higher than 100 mmHg; 4) the threshold pressure was little lower than the maximal secretory pressure measured by electrical stimulation of the parasympathetic secretory nerve (the chorda tympani); 5) there is no differences in the threshold pressures between afferents in the sympathetic and parasympathetic nerve routes; 6) when Bradykinin was infused from the duct, the afferent nerve discharged vigorously. Previous histochemical studies show that substance P and CGRP-containing nerves considered as possible afferent fibers were identified frequently around small ducts and blood vessels. We speculate that the afferent activity may relate to monitoring of excessive pressure of the fluid secretion and blood flow, or to pain due to salivary stone. [J Physiol Sci. 2006;56 Suppl:S186]
