Anandamide injected into the lateral ventricle of the brain inhibits submandibular salivary secretion by attenuating parasympathetic neurotransmission

J Fernandez-Solari,S.R Bornstein,V Rettori,J.P Prestifilippo,M Ehrhart-Bornstein,J.C Elverdin,P Vissio

doi:10.1590/s0100-879x2009000600010

J Fernandez-Solari, S.R Bornstein + Show 5 more

Open Access

https://doi.org/10.1590/s0100-879x2009000600010

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Abstract

Our objective was to determine the effect of arachidonylethanolamide (anandamide, AEA) injected intracerebroventricularly (icv) into the lateral ventricle of the rat brain on submandibular gland (SMG) salivary secretion. Parasympathetic decentralization (PSD) produced by cutting the chorda tympani nerve strongly inhibited methacholine (MC)-induced salivary secretion while sympathetic denervation (SD) produced by removing the superior cervical ganglia reduced it slightly. Also, AEA (50 ng/5 microL, icv) significantly decreased MC-induced salivary secretion in intact rats (MC 1 microg/kg: control (C), 5.3 +/- 0.6 vs AEA, 2.7 +/- 0.6 mg; MC 3 microg/kg: C, 17.6 +/- 1.0 vs AEA, 8.7 +/- 0.9 mg; MC 10 microg/kg: C, 37.4 +/- 1.2 vs AEA, 22.9 +/- 2.6 mg). However, AEA did not alter the significantly reduced salivary secretion in rats with PSD, but decreased the slightly reduced salivary secretion in rats with SD (MC 1 microg/kg: C, 3.8 +/- 0.8 vs AEA, 1.4 +/- 0.6 mg; MC 3 microg/kg: C, 14.7 +/- 2.4 vs AEA, 6.9 +/- 1.2 mg; P < 0.05; MC 10 microg/kg: C, 39.5 +/- 1.0 vs AEA, 22.3 +/- 0.5 mg; P < 0.001). We showed that the inhibitory effect of AEA is mediated by cannabinoid type 1 CB1 receptors and involves GABAergic neurotransmission, since it was blocked by previous injection of the CB1 receptor antagonist AM251 (500 ng/5 microL, icv) or of the GABA A receptor antagonist, bicuculline (25 ng/5 microL, icv). Our results suggest that parasympathetic neurotransmission from the central nervous system to the SMG can be inhibited by endocannabinoid and GABAergic systems.

Highlights

The submandibular gland (SMG) is one of the major salivary glands, together with the sublingual and the parotid glands
Δ saliva was significantly higher in Parasympathetic decentralization (PSD) and PSD plus sympathetic denervation (SD) rats compared to SD rats, when secretion was induced by 3 and 10 μg/kg of MC
Addiwww.bjournal.com.br tionally, it was shown that the β-adrenoreceptor agonist isoproterenol injected icv increased salivary flow, demonstrating the participation of a central adrenergic system in the regulation of salivary secretion [32]

Summary

Introduction

The submandibular gland (SMG) is one of the major salivary glands, together with the sublingual and the parotid glands. The sympathetic nervous system induces salivary secretion by releasing norepinephrine that stimulates α- and β-adrenergic receptors [2]. It was reported that pilocarpine, a muscarinic agonist, injected intracerebroventricularly (icv) induced salivary secretion by activating central autonomic efferent fibers [3]. Lesions of the lateral or ventromedial hypothalamus impair salivary secretion induced by increased ambient temperature in rats [5,6]. Other experiments have demonstrated that warming or electrical stimulation of the preoptic area produces an increase in salivary secretion by the submandibular and sublingual glands [7], and lesions in the anteroventral third ventricle region reduce salivary secretion induced by pilocarpine injected intraperitoneally (ip) or icv [3]

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