The Secretory Innervation of the Parotid Gland of the Cat: An Unexpected Component

Ekström, Jørgen; Emmelin, N.

doi:10.1113/expphysiol.1974.sp002237

Cited by 20 publications

(9 citation statements)

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“…The parotid gland of the cat has a sparse supply of sympathetic secretory fibres and these act mainly on 3-adrenoceptors but to a small and varyiing degree also oIn a-receptors [see Ekstr6m and Emmelin, 1974;Thulin, 1975]. The present observationis on the effects of symnpathetic stimulation and sympathomimetic drugs on a slow secretion elicited by auriculo-temporal stimulation or pilocarpine injection are compatible with this view.…”

Section: Parotid Glandssupporting

confidence: 79%

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Secretory Responses to Sympathetic Stimulation of the Cat's Salivary Glands in a State of Resting Secretion

Emmelin¹,

Gjörstrup²

1975

Exp Physiol

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The secretory effect of sympathetic stimulation on the cat's submaxillary gland was augmented greatly when studied against a background of slow secretion evoked by parasympathetic stimulation at a low frequency and imitating the slow resting secretion normally present in the waking state. The sympathetic secretory threshold was markedly lowered, and even at low frequencies sympathetic stimulation caused a large, wellmaintained response. After an x-adrenoceptor blocking drug sympathetic stimulation alone lost its secretory effect, but during resting secretion part of the accelerating effect was found to remain; this effect was elicited via P-adrenoceptors. A marked secretory effect of sympathetic stimulation was also obtained during resting secretion in the parotid gland, where the sympathetic secretory effect is normally very small.The salivary responses to electrical stimulation of the cervical sympathetic trunk are usually not very impressive, although salivary glands are generally assumed to receive not only parasympathetic but also sympathetic secretory nerves. After a fairly long latency flow starts, but this, in most glands, is slow and often tends to decline and even cease despite continued stimulation. This applies, for instance, to the submaxillary gland of the dog, and in the parotid of this species no secretion at all, or very little, results from sympathetic excitation. However, in recent experiments on these two glands quite a different picture was obtained when attempts were made to study the sympathetic effect under conditions thought to be more physiological than in previous studies [Emmelin and Gj6rstrup, 1975]. The slow resting secretion normally present in the waking state and induced by way of the parasympathetic nerves [see Babkin, 1950] was reproduced by stimulating these nerves at a low frequency, and the effect of sympathetic stimulation was observed against such a secretory background activity. Further, by injecting an a(-adrenoceptor blocking drug the vasoconstriction was prevented. This vasoconstriction is normally obtained on electrical excitation ofthe sympathetic trunk and might interfere with secretion; it does not belong to the response when the sympathetic secretory mechanism is activated in the course of physiological events [see Emmelin and Engstr6m, 1960]. When the a-adrenoceptor was blocked sympathetic stimulation had a marked, ,B-adrenoceptor mediated, secretory effect both in the submaxillary and the parotid gland of the dog.In the present investigation the secretory effect of sympathetic stimulation was studied in the cat's submaxillary gland during resting secretion. No oc-blocking drug was given initially, since in this gland sympathetic secretion is elicited via oc-adrenoceptors [see Emmelin, Schneyer and Schneyer, 1973] and not as in the dog via /-adrenoceptors [Emmelin and Holmberg, 1967]. Abolition of vasoconstriction was considered less important as the sympathetic 325 VOL. LX, No. 4 -1975 2

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Section: Parotid Glandssupporting

confidence: 79%

Section: Parotid Glandsmentioning

confidence: 99%

Secretory Responses to Sympathetic Stimulation of the Cat's Salivary Glands in a State of Resting Secretion

Emmelin¹,

Gjörstrup²

1975

Exp Physiol

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“…The right parotid cannula was then replaced by another cannula of a similar type supplied with a three-way tap to which a syringe could be attached. Eserine sulphate, 200 ,ug in 0-2 ml saline solution, was injected into the gland during 5 sec; 5 sec later the tap was turned so as to allow saliva to flow out, and the drops of saliva were recorded for a period of 15 min [Emmelin, Muren and Str6mblad, 1954;Ekstr6m and Emmelin, 1974]. Thereafter an additional dose of 5 mg/kg hexamethonium was given and the same procedure was applied to the left parotid gland.…”

Section: Methodsmentioning

confidence: 99%

Uncharted Cholinergic Nerves in the Rabbit Parotid Gland

Alm

Ekström

1976

Exp Physiol

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Cholinergic nerves are shown to be left in the rabbit parotid gland after avulsion of the auriculo-temporal nerve: a cholinesterase inhibitor injected through the duct caused secretion, thereby revealing leakage of acetylcholine from cholinergic nerve endings, and acetylcholinesterase positive nerves were found histochemically. The incomplete cholinergic denervation offers an explanation to the fact that some choline acetyltransferase activity remains in the 'denervated' glands.In the rabbit parotid glands a rapid and profound fall in the activity of the acetylcholine synthesizing enzyme, choline acetyltransferase, was found by Nordenfelt [1964] to follow a parasympathetic denervation, caused by section of the auriculo-temporal nerve. This finding probably indicates a neuronal localization for the enzyme. However, some enzyme activity usually remained suggesting either the presence of unsevered cholinergic neurones or other sources for the enzyme in the gland. In such denervated parotid glands of other species, i.e. cats [Nordenfelt, 1963; Ekstrom and Emmelin, 1974], dogs [Ekstrom and Holmberg, 1972] and rats [Ekstrom, 1974] a low choline acetyltransferase activity may be demonstrated also. In cats and dogs the residual enzyme activity seems to be accounted for, since several investigations, both physiological and histochemical, show that the denervation is incomplete leaving some cholinergic nerve fibres intact [Emmelin and Str6mblad, 1958;Emmelin and Holmberg, 1967;Garrett, 1966;Garrett and Holmberg, 1972;Holmberg, 1972; Ekstrom and Emmelin, 1974]. Accordingly, by including not only section of the auriculo-temporal nerve in the denervation procedure, but division of nerve strands on the internal maxillary artery [Holmberg, 1971] and the facial nerve the choline acetyltransferase activity of the parotid gland of dogs in most cases reached values below the limit of detection [Ekstrom and Holmberg, 1972].The present experiments investigate whether in rabbits also there are some cholinergic neurones left following avulsion of the auriculo-temporal nerve. This was done by the use of a cholinesterase inhibitor injected through the duct into the gland; such a substance is known to cause secretion of saliva by preserving acetylcholine leaking from the nerve endings [Emmelin and Stromblad, 1958]. Further, nerves stained for acetylcholinesterase were looked for. METHODSSixteen rabbits of both sexes weighing 1-9-3-2 kg were used. Under ether and pentobarbitone (35 mg/kg i.p.) anaesthesia the following experimental procedures were 127

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“…However in our study the histological changes in the glands were similar whether the denervation was, judged from secretory data, complete or partial; sheep 9 was an exception as there was no significant difference in nuclear-to-cytoplasmic ratios in the two glands. Ekstrom and Emmelin [1974b] discuss the presence of other parasympathetic innervations to the parotid gland of the cat and have established that secreto-motor fibres may course along the internal maxillary artery in this species. There is no evidence available yet of such extra routes for reflex parasympathetic secretion in ruminants; it remains however, a possibility and could explain the partial denervations.…”

Section: Discussionmentioning

confidence: 99%

Secretory and Structural Changes in the Parotid Salivary Gland of Sheep and Lambs After Parasympathetic Denervation

1975

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The effect of the parasympathetic nerve supply on the development of the parotid gland in the immature lamb and its maintenance in the adult sheep has been investigated by unilateral postganglionic denervation. Seventy-seven to ninety-three days after denervation secretory activity of the gland was examined and material taken for histological examination. The adult denervated glands secreted at lower rates than the innervated and their atropine-resistant secretory flow was reduced to as low as one fifth of that of the innervated glands. In two lambs an atropine-resistant flow did not develop in the denervated glands: in another two, flows of saliva from the denervated glands were present but were much less than in the contralateral innervated glands. After denervation glands were, with one exception, smaller than the contralateral innervated glands. The acinar cells of the denervated adult and lamb glands were smaller than the cells of the innervated glands but similar in size to those of 7-14 day old unoperated control lambs. Acinar cells in denervated glands had periodic acid Schiff staining material but the staining reaction to pyronin-methyl green was similar in the innervated and denervated. The results indicate that the integrity of the parasympathetic innervation is essential for the development of the parotid gland of the sheep and for its maintenance in the adult animal.The adult ruminant parotid salivary gland has a profuse serous secretion of similar osmolality to plasma. The voluminous output [Kay, 1960a] includes a spontaneous secretion which persists after denervation of the glands, or the administration of autonomic blocking agents and has been demonstrated in the excised perfused gland. Evidence on these features of the activity of the glands and on the contribution their secretions make to the maintenance of stable conditions in the more cranial parts of the stomach where fermentative digestion of plant material occurs, has been reviewed by Kay [1966].The parotid salivary gland of the new-born ruminant is histologically immature and has little secretory activity [Kay, 1960b] until the ingestion of solid food commences. Its development has been associated with the ingestion of solid material [Wilson, 1963]. The more cranial divisions of the stomach are also immature in the newly born ruminant and their more complete development occurs as fermentative digestion due to micro-organisms becomes established. Chemical and mechanical stimuli that have been shown to exert direct effects on the stomach [Brownlee, 1956;Harrison, Warner, Sander and Loosli, 1960;Warner and Flatt, 1965] have a special role in this.We sought in the present experiments to determine the effects of the parasympathetic innervation on the development of the secretion and structure of the parotid salivary glands of the lamb and on the maintenance of the secretion and structure in the adult. 223 IC ) .L I ILJA ,

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The Secretory Innervation of the Parotid Gland of the Cat: An Unexpected Component

Cited by 20 publications

References 9 publications

Secretory Responses to Sympathetic Stimulation of the Cat's Salivary Glands in a State of Resting Secretion

Secretory Responses to Sympathetic Stimulation of the Cat's Salivary Glands in a State of Resting Secretion

Uncharted Cholinergic Nerves in the Rabbit Parotid Gland

Secretory and Structural Changes in the Parotid Salivary Gland of Sheep and Lambs After Parasympathetic Denervation

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