MODE OF THE SYMPATHETIC INNERVATION OF THE SALIVARY GLANDS IN DOG

Abstract

Best and Taylor (1) quoted in their textbook, that the secretory function of the gland is regulated in two ways, one being nervous and the other hormonal. When the quick response is required, it is regulated ordinarily by the former, otherwise, however, by the latter. But there is no experimental evidence in respect to the significance of either regulations of the salivary secretion in any literature.
Anatomically the salivary glands are innervated by two nervous systems, i.e., the parasympathetic and the sympathetic. Since the works of Bernard (2), and Heidenhain (3) it has been conclusively decided that the secretory nerves of the glands are cholinergic.
Some questions on the mode of the sympathetic innervation of the glands yet remain to be settled. Although the salivary flow of the submaxillary or parotid gland was caused by the systemic administration of adrenaline or noradrenaline by Langley (4), Emmlin and Stromblad (5), the secretion thus obtained was less in volume except with the parotid gland of the cat. The amount of the drugs required to induce the secretion were 10 to 20 γ/kg (6). By electrical stimulation of the cervical sympathetic nerve the liberation of adrenaline-like substances in the gland was proved by Cattell (7). From these results, it is described in many textbooks of physiology that the sympathicus is also the secretory nerve of the salivary glands.
While the parasympathetic saliva is serous and poor in organic substances, the sympathetic saliva is mucous and rich in organic substances. Originating from the histological studies of Stormont (8) and Rawilson (9), that the serous cell which is seen in the submaxillary and the parotid glands is innervated by the parasympathetic, and the mucous cell which is seen in the submaxillary and the sublingual glands is innervated by the sympathetic, and that the composition of the saliva secreted accords with the variety of the secretory cell stimulated and further that each cell responds to each stimuli in a characteristic histological change, Babkin (10) set up the innervating and the secretory theory of the salivary glands. Based on the studies on the potential change of the cells of the submaxillary gland during secretion Langenskiöld (11) concluded that each cell of the gland is innervated by both nerves.
The most potentially supporting evidence of Babkin's theory that the sympathicus is also a secretory nerve is a so-called paralytic secretion (12) which was detected by Bernard for the first time and has been widely investigated. Although chorda denervation of the glands sensitizes the response to adrenaline and noradrenaline, the salivary secretion in response to the drugs is less in volume in comparison with the response to stimulation of the parasympathetic nerve. Moreover the physiological significance of the phenomenon still remains a question. Therefore it may be concluded that the sympathicus is also a secretory nerve of the glands.
In the course of studies on the action of ganglion blocking agents upon the salivary secretion in the dog (13), the authors noticed some different effects of adrenaline and noradrenaline. Systematic studies of the mode of the sympathetic innervation of salivary glands are planned, but in this report the studies on the secretory response of the submaxillary gland will be mainly described.