Chorda-lingual Nerve Stimulation Research Articles

The influence of estrogen and progesterone on parasympathetic vasodilatation in the rat submandibular gland

Previous studies suggest that NO- and PGI 2-independent pathways play a greater role in parasympathetic vasodilatation in the submandibular glands (SMG) of female than of male rats. Thus, the purpose of this study was to determine whether estrogen and progesterone influence the relative contributions of NO and PGI 2 to parasympathetic vasodilatation in the SMG. Vascular responses to chorda-lingual nerve stimulation were examined in sham-operated (SHAM) and ovariectomized (OVX) female rats and in OVX rats treated with either 17β-estradiol alone or a combination of 17β-estradiol and progesterone. Compared with SHAM animals, increases in vascular conductance in OVX rats were reduced at 1, 2 and 5 Hz ( p < 0.05). Blood flow responses in OVX + 17β-estradiol and OVX + 17β-estradiol + progesterone rats were indistinguishable from those observed in SHAM animals. Indomethacin had no effect on vasodilatation in SHAM and OVX + 17β-estradiol rats, but increased vascular responses in OVX animals ( p < 0.02). The addition of L-NAME resulted in a significant reduction in vasodilatation at all frequencies. In OVX rats treated with both estrogen and progesterone, indomethacin caused a reduction in vasodilatation and L-NAME further diminished the remaining responses. Under all conditions, vasodilatation was due largely, if not exclusively, to direct parasympathetic rather than antidromic sensory nerve activation. Finally, both neuronally-derived and endothelium-derived NO appeared to be responsible for the NO-dependent vasodilatation, but endothelium-derived NO became increasingly important as the frequency of stimulation increased. We conclude that estrogen and progesterone influence parasympathetic vasodilatation through combined effects on NO-, PGI 2- and non-NO/PGI 2-mediated pathways.

Differences in parasympathetic vasodilator and salivary responses in the cat submandibular gland between lingual and chorda-lingual nerve stimulation.

Experimental activation of parasympathetic vasodilatation and salivation in the submandibular gland by a "pseudoreflex" method has definite advantages over other commonly used methods. However, it is unclear which stimulation sites allow for avoidance of direct activation of the parasympathetic efferents to this gland. We examined this question in heavily anesthetized (alpha-chloralose and urethane), artificially ventilated, cervically vago-sympathectomized cats, using the intersection of the chorda-lingual nerve and the submandibular gland duct ("the intersection") as our reference point. Both vasodilatation and salivation evoked by electrical stimulation of the lingual nerve were abolished by section of the chorda-lingual nerve (10 mm proximal to the intersection), provided the stimulation site was distal to the intersection by 4 mm or more. This salivation was abolished by the muscarinic receptor antagonist, scopolamine. Thus, by careful choice of stimulation site, submandibular gland responses mediated solely by reflex parasympathetic mechanisms can be evoked by lingual nerve stimulation in this preparation.

Peroxidase and kallikrein in atropine-resistant secretion of submandibular saliva on parasympathetic nerve stimulation in anaesthetized rats.

Flow of submandibular saliva and the constituents secreted during chorda-lingual nerve stimulation at 40 Hz (3 x 10 min) were studied after alpha- and beta-adrenergic blockade, and in the absence (control) or presence of cholinergic blockade in anaesthetized rats. Peroxidase and true tissue kallikrein (rK1) were assessed to gain insight into the effects of the non-adrenergic, non-cholinergic (NANC) transmitters on protein secretion by acini and granular tubules, respectively. From control glands there was an overall mean flow of 181 +/- 15 microliters g-1 min-1, with no significant differences between the three periods. Secretion from atropinized glands was approximately 20% of that from control glands in the first 10 min, decreasing progressively to approximately 6% in the final period. Protein outputs from control glands showed no significant differences for the three periods (0.23 +/- 0.05 mg g-1 min-1). Protein outputs from atropinized glands were similar to controls in the first 10 min and then decreased significantly. Peroxidase output from control glands increased progressively (from 31 +/- 7 to 243 +/- 68 pmol dichlorofluorescein (DCF) g-1 min-1) but in saliva from atropinized glands the overall mean output was only 4.5 +/- 0.8 pmol DCF min-1 ml-1, with a progressive decrease between samples. Outputs of rK1 from control glands were similar for all samples (20.6 +/- 4.0 nmol AFC g-1 min-1), but there was a significantly smaller and decreasing output of rK1 from atropinized glands. In conclusion, NANC transmitters released from parasympathetic nerves during stimulation at high frequency appear to have little influence on the secretion of protein from rat submandibular acini and granular tubule cells when acting in isolation. This contrasts with their effects on amylase secretion from rat parotid glands under similar circumstances.

The role of nitric oxide in the control of protein secretion in the submandibular gland of the cat.

Submandibular salivary responses to stimulation of the parasympathetic chorda lingual innervation have been investigated in anaesthetized cats in the presence and absence of N omega-arginine-L-methyl ester (L-NAME) to block the synthesis of nitric oxide. Stimulation either at 2 Hz continuously or at 20 Hz for 1 s at 10 s intervals produced an abrupt fall in submandibular vascular resistance and initiated a flow of submandibular saliva. Neither of these responses differed significantly from the other but the output of protein was significantly potentiated (P < 0.05) when the high-frequency intermittent pattern of stimulation was employed. This potentiation of protein output was abolished in the presence of L-NAME, when the output of protein from the gland was closely similar, whichever pattern of stimulation was employed. Additional administration of atropine completely blocked all submandibular responses to parasympathetic stimulation showing that, in the presence of L-NAME, each response was due to release of acetylcholine acting on muscarinic receptors. The intermittent pattern of chorda lingual nerve stimulation produced a significant rise in the output of vasoactive intestinal peptide (VIP) from the gland (P < 0.01) and this response was significantly reduced following administration of L-NAME (P < 0.05). The results are consistent with the contention that stimulation of the parasympathetic innervation in bursts, which increases the amount of VIP released from the postganglionic nerve terminals, enhances the output of protein in submandibular saliva in the cat. The mechanism involves nitric oxide (NO), which may act, at least in part, presynaptically by modulating VIP release.

Salivary secretion in cat submandibular gland mediated by chorda tympani afferents.

The aim of the present study was to investigate whether the afferent traffic from the tongue mediated only via the chorda tympani nerve (CTN) can still elicit reflex salivary and vasodilator responses in the cat submandibular gland (SMG) after section of the lingual nerve proper (LNP). Electrical stimulation of the chorda lingual nerve (CLN) at a site approximately 5 mm distal to the intersection of the CLN and the SMG duct elicited salivary and vasodilator responses in the SMG in sympathectomized cats. Both responses were unaffected by section of the LNP. The optimal frequency of CLN stimulation for submandibular salivation and vasodilation was 20 Hz, regardless of whether the LNP had been cut. Prior treatment with the autonomic ganglion blocker hexamethonium (10 mg/kg iv) virtually abolished the salivation and the blood flow increase in SMG. Prior treatment with scopolamine (0.1 mg/kg iv) almost abolished the salivary secretions but had no effect on the vasodilator responses in the SMG elicited by CLN stimulation after LNP section. The mechanism underlying the reflex submandibular salivation mediated by chorda tympani afferents appears to involve parasympathetic muscarinic receptors, but the mechanism for the vasodilator response has yet to be established. These results indicate that afferent traffic passing through the CTN on CLN stimulation is importantly involved in the parasympathetic reflex secretory and vasodilator responses in the cat SMG.

Parasympathetic-mediated reflex salivation and vasodilatation in the cat submandibular gland

The aim of the present study was to compare and characterize the secretory and vasodilator effects induced by chorda lingual nerve (CLN) stimulation (i.e., direct parasympathetic stimulation) and reflex parasympathetic stimulation in the submandibular gland (SMG) of sympathectomized cats. The increase in blood flow and salivary secretion in response to electrical stimulation of the central cut ends of the vagus and inferior alveolar nerves, as well as to stimulation of the CLN at a site approximately 5 mm distal to the intersection of the CLN and the SMG duct (site D) was completely abolished by section of the chorda tympani nerve (CTN). Neither response to CLN stimulation at a site nearly 5 mm proximal to the intersection of the CLN and the SMG duct (site C) was affected by CTN section. Section of the CLN at a site approximately 5 mm distal to the intersection of the CTN and the CLN abolished the submandibular salivary and vasodilator responses elicited by CLN stimulation at site D but had no effect on the two responses evoked by CLN stimulation at site C. The blood flow increases evoked by electrical stimulation of the CLN at site D were greatly reduced by prior treatment with the autonomic ganglion blocker hexamethonium, but the vasodilator responses evoked from site C were reduced much less. These data suggest that the secretory and vasodilator responses elicited by CLN stimulation at site D and those by vagus and inferior alveolar nerve stimulation are mediated largely via a parasympathetic reflex mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of avian pancreatic polypeptide as a VIP antagonist

Vasoactive intestinal polypeptide (VIP) has been shown to be present in some neurones of the myenteric plexus by immunohistochemical techniques. It was reported that avian pancreatic polypeptide (APP) inhibited the vasodilation induced by VIP and chorda-lingual nerve stimulation in the cat submandibular gland (Lundberg et al.,Acta.Physiol.Scand.,1980,110,199). The purpose of the present experiment is to investigate whether APP acts as a VIP antagonist by using various tissues innervated by non-cholinergic, non-adrenergic nerves in the gastrointestinal tract. APP was isolated and purified from chicken pancreas by the method of Kimmel et al. (J.Biol.Chem., 1975,250,9369). The isolated APP (0.48-12nmole) caused a dose-dependent inhibition of the vasodilation induced by VIP and chorda-lingual nerve stimulation in the cat submandibular gland as reported by Lundberg et al. ‘1980). In the cat colon, APP (0.4-10nmole) elicited a dose-dependent vasoconstriction and partially inhibited the atropine-resistant vasodilation induced by VIP and pelvic nerve stimulation, but not significantly that induced by bradykinin. On the other hand, APP failed to inhibit the relaxation caused by either transmural electrical stimulation or VIP in the presence of atropine and guanethidine in isolated chick rectum and fundic strips of guinea-pig and rat. Furthermore, APP had no inhibitory effect on the gastric relaxation induced by the vago-vagal reflex and by the close arterial injection of VIP in the dog stomach. The results suggest that APP may act as an antagonist for the VIP-induced vasodilation of vascular smooth muscles, but not for the VIP-and the non-adrenergic nerve stimulation-induced relaxation of gastrointestinal smooth muscles.

Pharmacological analysis of salivary and blood flow responses to histamine of the submandibular gland of the dog.

1 The submandibular gland in situ was perfused with blood through the glandular artery at constant pressure in anaesthetized dogs. Drugs were administered intra-arterially. 2 Histamine produced both salivation and an increase in blood flow, each response having an early and a late component. 3 Marked tachyphylaxis to histamine developed in both of the salivary responses but only in the late blood flow response to histamine. 4 The early and late salivary responses were abolished and the late blood flow response was diminished by infusion of tetrodotoxin in doses that abolished the salivary and blood flow responses to electrical stimulation of the chorda-lingual nerve. 5 The whole salivary response to histamine was abolished by infusion of (--)-hyoscyamine in doses that greatly antagonized the salivary and blood flow responses to acetylcholine, whereas the blood flow responses to histamine were scarcely modified. These doses of (--)-hyoscyamine abolished the salivary response to chorda-lingual nerve stimulation but left the blood flow response to it unaffected. 6 The salivary and blood flow responses to histamine were unaffected by infusion of hexamethonium in doses that almost abolished the salivary and blood flow responses to chorda-lingual nerve stimulation. 7 The whole salivary response to histamine was abolished and the late blood response to histamine was partially inhibited by the histamine H1-receptor antagonist, mepyramine, but not by the histamine H2-receptor antagonist, metiamide. 8 The early blood flow response to histamine was antagonized by both mepyramine and metiamide but mepyramine was far more effective than metiamide. 9 These results led to the following conclusions: (1) the whole salivary response and a part of the late blood flow response to histamine are due entirely to excitation of parasympathetic postganglionic neurones; (2) neuronal histamine receptors involved are exclusively of the H1-type; (3) histamine has no direct stimulant action on the glandular cells; (4) the early blood flow response and the remaining part of the late blood flow response to histamine result from the direct action on vascular smooth muscle in the glandular vascular bed; (5) vascular histamine receptors consist of H1- and H2-receptors.

SECRETORY, MOTOR AND VASCULAR EFFECTS IN THE SUBLINGUAL GLAND OF THE RAT CAUSED BY AUTONOMIC NERVE STIMULATION

The influence of the autonomic nerves on sublingual glands of rats was studied. Stimulation of the chorda-lingual nerve evoked a lively flow of saliva and was also thought to contract the myoepithelial cells in the gland. Sympathetic nerve stimulation, on the other hand, usually evoked no secretion and did not cause any motor responses in the sublingual gland. The glandular blood flow was increased by chorda-lingual nerve stimulation, and this vasodilatation persisted also when atropine had been administered. Sympathetic nerve stimulation decreased the sublingual blood flow; this vasoconstrictor effect was mediated via activation of alpha-adrenoceptors.

BRADYKININ AND FUNCTIONAL VASODILATATION IN THE SALIVARY GLAND

Blood flow through the submandibular gland of the dog was measured and the venous effluent monitored for potential mediators of the functional vasodilatation by passing it over a series of assay tissues. On chorda lingual nerve stimulation there was salivation, an increased blood flow and the release of a bradykinin-like substance (kinin) into the venous effluent. In about half of the preparations, increasing the frequency of stimulation from 2 to 10 Hz led to an increased output of kinin, whereas in the others successive stimulations led to a decreasing output of kinin in the face of normal secretory and vascular responses. Following the administration of atropine, the vasodilatation persisted, salivation was abolished and after several stimulations kinin release could no longer be detected. Release of prostaglandin did not appear to be responsible for the vasodilatation. It is concluded that neither kallikrein nor kinin is the main mediator of parasympathetic vasodilatation in the salivary gland.

The effect of chronic duct ligation on the vascular and secretory responses of the cat's submaxillary gland.

1. The object of the present experiments was to re-investigate the role of kallikrein in functional hyperaemia in the submaxillary gland of the cat. Kallikrein concentration in the gland and saliva was reduced by ligation of the duct for 2-3 days before the acute experiment, at which time the duct was cannulated proximal to the ligation and blood flow and salivation measured.2. Despite the fall in kallikrein concentration, a normal two-phase vascular response was obtained on continuous stimulation of the chorda-lingual nerve at 1-5 Hz and the progressive increase in blood flow to a constant level characteristic of 10 and 20 Hz stimulation was also seen. Quantitatively, the increase in blood flow following a 10 sec stimulation was reduced to about 75% of control values at all stimulation frequencies used and the maintained vasodilatation was reduced when using continuous stimulation at 1 Hz but not at 10 and 20 Hz.3. The supersensitivity to the vasodilator properties of bradykinin, previously reported to follow duct ligation, was confirmed.4. The increased blood flow produced by chorda-lingual nerve stimulation could be delayed by circulatory arrest. Evidence was obtained suggesting that the vascular response to chorda stimulation delayed by arterial occlusion was not mediated by kallikrein alone.5. It was concluded that kallikrein was not the sole mediator of functional hyperaemia in the cat submaxillary gland but that a combination of vasodilator nerves and kallikrein release explained more phenomena than either hypothesis alone.

Dependence of functional vasodilatation in the cat submaxillary gland upon stimulation frequency.

1. Submaxillary gland blood flow and salivation have been measured in anaesthetized cats and the chorda-lingual nerve has been stimulated at different frequencies.2. At low stimulation frequencies (1-5 Hz) there was a large transient increase in blood flow followed by a more modest maintained increase which lasted as long as stimulation continued. Stimulation at 10-20 Hz also produced a rapid initial increase in flow but at these frequencies the subsequent decline was not seen and a gradual further increase to a maintained level was observed.3. Atropine in small doses depressed both the transient and the maintained response to low frequency stimulation but at 10-20 Hz the maintained vasodilatation was unaffected by the drug.4. The transient increase in potassium concentration in saliva and venous blood draining the gland was not correlated with the vascular response.5. In conclusion, further details have been provided concerning the vascular response to chorda-lingual nerve stimulation and its sensitivity to atropine. Functional vasodilatation is not secondary to potassium release and is not due to a direct interaction between rate of saliva production and rate of blood flow although the vasodilatation does appear to be related in part to the acompanying salivation.