title: Effect of pilocarpine on the formalin-induced orofacial pain in rats.
abstract: In this study, the effects of subcutaneous (SC) injection of pilocarpine (a cholinomimetic agent) and atropine (a muscarinic receptors antagonist) were investigated on a tonic model of orofacial pain in rats. The contribution of the endogenous analgesic opioid system was assessed using naloxone (an opioid receptors antagonist). Tonic orofacial pain was induced by SC injection of a diluted formalin solution (1%, 50 μL) in the right upper lip, and the time spent face rubbing was measured in five min blocks for 1 h. Formalin induced a biphasic (first phase: 0-5 min and second phase: 15-35 min) pain response. Pilocarpine significantly (P < 0.05) suppressed both phases of orofacial pain. Atropine did not have any effect and naloxone non-significantly increased the intensity of pain when used alone. In the pre-injection examinations, atropine prevented, but naloxone did not reverse the antinociceptive effect of pilocarpine. The results indicated that SC injection of formalin in the orofacial region induced a marked biphasic pain. Pilocarpine via muscarinic cholinergic receptors produced antinociceptive effect in the orofacial formalin-induced pain. The endogenous opioid analgesic system may not have a role in pilocarpine-induced antinociception.
authors: Department of Basic Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran.
authors: Esmaeal
authors: E
authors: Tamaddonfard
authors: Department of Basic Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran.
authors: Amir
authors: A
authors: Erfanparast
authors: Department of Basic Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran.
authors: Emad
authors: E
authors: Khalilzadeh
keywords: Atropine; Naloxone; Orofacial pain; Pilocarpine; Rat
references: J Korean Med Sci. 2001 Aug;16(4):498-504
references: 11511797
references: Anesthesiology. 2004 Mar;100(3):690-6
references: 15108987
references: Anesth Analg. 1999 Aug;89(2):428-33
references: 10439760
references: Biochem Biophys Res Commun. 2009 Feb 20;379(4):975-9
references: 19135983
references: Brain Res. 2005 Jan 25;1032(1-2):149-53
references: 15680953
references: Methods Find Exp Clin Pharmacol. 1999 Oct;21(8):523-7
references: 10599050
references: Pain. 1995 Apr;61(1):11-6
references: 7644233
references: Phytother Res. 2010 Mar;24(3):410-3
references: 19653196
references: Neuropharmacology. 2007 Aug;53(2):197-206
references: 17543355
references: Phytomedicine. 2008 Aug;15(8):630-4
references: 18164607
references: Eur J Pharmacol. 2009 Mar 1;605(1-3):57-62
references: 19168053
references: Pain. 2003 Jul;104(1-2):367-73
references: 12855347
references: J Anesth. 2007;21(1):31-6
references: 17285410
references: Neurosci Lett. 1989 Sep 11;103(3):349-53
references: 2812522
references: Neuroscience. 1990;36(2):543-51
references: 2215933
references: J Neurosci Methods. 2004 Dec 30;140(1-2):39-46
references: 15589332
references: Exp Neurol. 1989 Oct;106(1):78-84
references: 2792300
references: J Neural Transm (Vienna). 2008;115(1):1-6
references: 17851635
references: Pharmacol Biochem Behav. 2005 Oct;82(2):338-44
references: 16213578
references: Neurosci Biobehav Rev. 2004 Apr;28(2):219-26
references: 15172765
references: Eur J Pharmacol. 2010 Feb 10;627(1-3):119-23
references: 19891965
references: Br J Pharmacol. 2004 Apr;141(7):1175-84
references: 15006904
references: Pain. 2002 Mar;96(1-2):81-7
references: 11932064
references: Pain. 1998 May;76(1-2):173-8
references: 9696471
references: Pain. 1995 Sep;62(3):295-301
references: 8657429
references: Vet Rec. 1997 May 24;140(21):553-7
references: 9185312
references: Brain Res. 2009 Nov 17;1298:145-52
references: 19728997
references: Pain Physician. 2008 Mar;11(2 Suppl):S133-53
references: 18443637
references: Anesth Analg. 1995 Sep;81(3):501-7
references: 7653812