Effects of duct ligation on choline acetyltransferase activity in salivary glands of rats

Experimental Physiology

2001

Postganglionic non-adrenergic, non-cholinergic (NANC) mechanisms are of importance for the responses of parasympathetic secretory impulses in salivary glands (Ekström, 1999a). In the parotid gland of the anaesthetised rat activation of these mechanisms results in exocytosis of acinar protein-storing secretory granules and secretion of saliva upon electrical stimulation of the parasympathetic innervation. These parasympathetic NANC mechanisms are of physiological significance as they are mobilised under reflex conditions in the conscious animal. In a series of experiments on the rat parotid gland, loss of acinar secretory granules was used to indicate reflexly elicited secretory activity (Ekström, 1999a). Whereas hard pelleted food caused acinar degranulation in the presence of atropine and a-and b-adrenoceptor antagonists, a liquefied form of the pelleted diet did not (Asztély et al. 1994). Therefore, it was concluded that the NANC-induced exocytotic event depended on masticatory-salivary reflexes rather than on gustatory-salivary reflexes. Recently, ascorbic acid applied on the tongue was found to evoke parasympathetic NANC-induced secretion of parotid saliva in the awake rat (Ekström, 1998). Thus, the aim of the present study was to investigate whether acid would reflexly elicit exocytosis of parotid acinar secretory granules and if so, whether the gustatory reflexes involved NANC transmission. METHODSA total of 37 adult female Sprague-Dawley rats (B & K Universal AB, Sollentuna, Sweden) were used. The animals were caged in groups of four in a room with lights on from 05.00 to 21.00 h and a temperature of 21°C. They had free access to a standard pelleted diet (B & K Universal). The night before the acute experiment, the animal was kept separately in a cage with a floor of wire netting and food, but not water, was withheld. The animals subjected to the acid stimulus were divided into the following groups: (1) innervated rats without pretreatment with blocking agents (mean body weight ± S.E.M. and number of observations, 285 ± 2 g, n = 7); (2) innervated rats pretreated with atropine, phentolamine and propranolol (276 ± 8 g, n = 8); (3) parasympathetically denervated rats pretreated with atropine, phentolamine and propranolol (290 ± 7 g, n = 5); (4) parasympathetically denervated rats pretreated with atropine (303 ± 5 g, n = 5); (5) parasympathetically denervated rats pretreated with phentolamine and propranolol (273 ± 1 g, n = 3). To study the effect of parasympathetic denervation per se, a group of eight rats (267 ± 4 g) not subjected to the acid was used. All protocols were carried out according to local ethical committee guidelines.The animals subjected to chronic denervation were anaesthetised with sodium pentobarbitone (50 mg kg _1 , I.P.) 7 days before the acute experiment. Parasympathetic denervation of the parotid gland on the right side was achieved by cutting the auriculotemporal nerve where it emerges from the base of the skull (Ekström, 1974; Alm & Ekström, 1976). Care was taken to avoid damage to t...

Section: Figurementioning

confidence: 49%

Gustatory‐Salivary Reflexes Induce Non‐Adrenergic, Non‐Cholinergic Acinar Degranulation in the Rat Parotid Gland

Experimental Physiology

2001

“…Section of the auriculo-temporal nerve reduced the activity of the acetylcholine-synthesizing enzyme choline acetyltransferase to I % (Banns et at., 1979) (Fig. 4).…”

Section: Resultsmentioning

confidence: 98%

“…SP- (Brodin et al, 1982), VIP- (Fahrenkrug and Schaffalitzky de Muckadell, 1977), and CGRP- (Grunditz et al, 1986) like immunoreactivities in the glands were determined by radioimmunoassay. Choline acetyltransferase activity was determined by a radioisotope method (Banns et al, 1979). The following drugs were used: atropine sulfate (Sigma Chemical Co., St. Louis, MO, USA), CGRP (Peninsula Labs, Belmont, CA, USA), dihydroergotamine methansulfonate (Sandoz AG, Basel, Switzerland), hexamethonium bromide (Pharma Rodia, Birkero5d, Denmark), methacholine chloride (Sigma), propranolol hydrochloride (ICI Pharmaceuticals, Macclesfield, UK), SK (Bachem, Basel, Switzerland), SP (Peninsula), (D-Arg', D-Pro2, D-Trp7'9, Leu")-SP (Peninsula), and VIP (Sigma).…”

Section: Introductionmentioning

confidence: 99%

Neuropeptides and Secretion

1987

J Dent Res

106

In the rat parotid gland, an atropine-resistant parasympathetic-nerve-evoked secretion was demonstrated in vivo. In the absence of atropine, the non-adrenergic, non-cholinergic transmitter release seemed to contribute to the fluid secretion and to be largely responsible for the secretion of amylase and acinar secretory granules. The gland was reached by nerve fibers containing substance P (SP), vasoactive intestinal peptide (VIP), and, to some extent, calcitonin-gene-related peptide (CGRP) via the parasympathetic auriculo-temporal nerve. Upon electrical stimulation of the nerve, these peptides were released. SP and substance K (SK), a novel tachykinin, induced a profuse watery secretion when injected i.v., while VIP caused a sparse but amylase-rich secretion. CGRP caused no secretion on its own. The tachykinin-evoked secretory response was enhanced by VIP and CGRP. A SP-analogue almost abolished the SP-evoked response, while the atropine-resistant parasympathetic response was only halved. None of the peptides under study can on its own account for the atropine-resistant parasympathetic secretion. The neuropeptides may play complementary roles in the regulation of the exocrine functions of the gland.

“…The incubation occurred under optimal conditions, and the medium was that of Banns et al (1979) but dithiotreitol was omitted; the control incubation contained acetylcholinesterase instead of the cholinesterase inhibitor eserine (physostigmine). Assays, both test and control, were carried out in duplicate, each tube containing 85 μl of the incubation medium and 25 μl of tissue homogenate.…”

Section: Methodsmentioning

confidence: 99%

“…The radioactivity was measured in a scintillation counter (LKB Wallac). The salivary gland homogenate does not only form radiolabelled acetylcholine but also radiolabelled acetylcarnitine (Banns et al 1979; Banns & Ekström, 1981). However, acetylcarnitine is not thought to be extracted by tetraphenylboron (Fonnum, 1975).…”

Section: Methodsmentioning

confidence: 99%

The otic ganglion in rats and its parotid connection: cholinergic pathways, reflex secretion and a secretory role for the facial nerve

Khosravani

Sandberg

Experimental Physiology

2005

Otic ganglionectomy in rats was found to have affected the parotid gland more profoundly than section of the auriculotemporal nerve as assessed by reduction in gland weight (by 33 versus 20%) and total acetylcholine synthesizing capacity (by 88 versus 76%) 1 week postoperatively and, when assessed on the day of surgery under adrenoceptor blockade, by reflex secretion (by 99 versus 88%). The facial nerve contributed to the acetylcholine synthesizing capacity of the gland. Section of the nerve only, at the level of the stylomastoid foramen, reduced the acetylcholine synthesis by 15% and, combined with otic ganglionectomy, by 98% or, combined with section of the auriculotemporal nerve, by 82%. The facial nerve was secretory to the gland, and the response was of a cholinergic nature. The nerve conveyed reflex secretion of saliva and caused secretion of saliva upon stimulation. Most of the facial secretory nerve fibres originated from the otic ganglion, since after otic ganglionectomy (and allowing for nerve degeneration) the secretory response to facial nerve stimulation was markedly reduced (from 23 to 4 microl (5 min)(-1)). The persisting secretory response after otic ganglionectomy, exaggerated due to sensitization, and the residual acetylcholine synthesizing capacity (mainly depending on the facial nerve) showed that a minor proportion of pre- and postganglionic nerve fibres relay outside the otic ganglion. The great auricular nerve, which like the facial nerve penetrates the gland, caused no secretion of saliva upon stimulation. Avulsion of the auriculotemporal nerve was more effective than otic ganglionectomy in reducing the acetylcholine synthesizing capacity (by 94 versus 88%) and as effective as otic ganglionectomy in abolishing reflex secretion (by 99%). When aiming at parasympathetic denervation, avulsion may be the preferable choice, since it is technically easier to perform than otic ganglionectomy.