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KMID : 0376219820190020141
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Chonnam Medical Journal
1982 Volume.19 No. 2 p.141 ~ p.150
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Inhibitory Effects of the Cervical Sympathetics on the Reflex Submaxillary Salivation in the Cat
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Abstract
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Since the time of Ludwig, Heidenhain and Langley the cervical sympathetic trunk has been assumed to carry specific secretory fibers for the submaxillary gland, although, unlike the salivary secretion elicited by stimulating the chorda tympani, response to stimulation of the cervical sympathetics was usually shortlasting and tended to cease in spite of continuous stimulation. However, copious salivation, induced by stimulation of the chorda tympani or by intravenous infusion of pilocarpine, was decreased by stimulation of the cervical sympathetics or by intravenous injection of catecholamine. If both sets of nerves, the chorda tympani and the cervical sympathetics, to the gland are to stimulate the secretory process, the physiological significance of the double innervation of the gland becomes obscured. On the other hand, it is conceivable that the nerves control structures in the gland other than the secretory cells and might thereby modify the secretion. A modified flow of saliva may be due to contractions of myoepithelial cells or to vascular changes caused by impulses in vasomotor nerves. Thus the role of the sympathetic innervation to the gland still remains unsettled. So far, most of investigations were performed only by observing the effects of stimulation of the efferent nerve pathways to the gland, and therefore, the results derived were not pertinent enough to substantiate the role of the nerves. However, it is well known that among the modes of the salivary secretion, the reflex salivation is the most common. Considering that the autonomic innervation to various organs and structures usually exerts a regulatory function, it seems toore, appropriate to study the function of the nerves distributed to the gland on the reflex salivation. In this study, the effects of stimulation of the cervical sympathetics with impulses of low or high frequencies on the reflex submaxillary salivation elicited by stimulating the afferent fibers of the pharyngeal branch of the vagus and lingual nerves were investigated to elucidate the role of the sympathetic innervation to the gland.
Cats were anesthetized with ketamine. Spontaneous salivation was not observed. Copious submaxillary salivation and increased blood flow elicited by stimulation of central end of the cut pharyngeal branch of the vagus or that of lingual nerve were not affected by stimulation of the cervcal sympathetics with impulses of low frequency (1-3Hz), whereas the responses were markedly decreased by the stimulation of the nerve with higher frequency (15-50Hz). These reflex salivation were not affected by severing of the sympathetics or pretreatment with phenoxybenzamine, while they were completely abolished by severing the chorda tympani or by administration of atropine. Copious salivary secretion induced by pilocarpine is markedly augmented by stimulation of the central end of the cut pharyngeal branch of the vagus and peripheral end of the cut chorda tympani, whereas the response was decreased by stimulating peripheral end of the cut cervical sympathetics. The reflex submaxillary salivation and increased blood flow by the stimulation of the afferent fibers of the lingual nerve were decreased by the ligation of the common carotid artery on the ipsilateral side and completely abolished by the ligation of the submaxillary artery.
These effects on the reflex salivation indicate that the cervical sympathetic trunk is not involved in the efferent pathway of the submaxillary secretion, reflexly evoked by stimulation of the afferent fibers of the pharyngeal branch of the vagus or the lingual nerve. It also suggests that the cervical sympathetics, at higher frequencies, inhibits the reflex submaxillary salivation by decreasing the blood flow to the gland which in turn is caused by the excitation of the sympathetic vasoconstrictor fibers. It is concluded that there are no evidences of existence of sympathetic secretory fibers for the submaxillary gland.
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KEYWORD
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