Thiago S Moreira1, Ana C Takakura2, José V Menani3, Eduardo Colombari3. 1. Department of Physiology and Biophysics, Institute of Biomedical Science, University of São Paulo, 05508-000, São Paulo, Brazil. Electronic address: tmoreira@icb.usp.br. 2. Department of Pharmacology, Institute of Biomedical Science, University of São Paulo, 05508-900, São Paulo, Brazil. 3. Department of Physiology and Pathology, School of Dentistry, Sao Paulo State University, 14801-903, Araraquara, Brazil.
Abstract
OBJECTIVE: Peripheral treatment with the cholinergic agonist pilocarpine increases salivary gland blood flow and induces intense salivation that is reduced by the central injection of moxonidine (α2-adrenoceptors/imidazoline agonist). In the present study, we investigated the effects of the intracerebroventricular (i.c.v.) injection of pilocarpine alone or combined with moxonidine also injected i.c.v. On submandibular/sublingual gland (SSG) vascular resistance. In addition, the effects of these treatments on arterial pressure, heart rate and on mesenteric and hindlimb vascular resistance were also tested. DESIGN: Male Holtzman rats with stainless steel cannula implanted into lateral ventricle and anaesthetized with urethane+α-chloralose were used. RESULTS: Pilocarpine (500nmol/1μl) injected i.c.v. Reduced SSG vascular resistance and increased arterial pressure, heart rate and mesenteric vascular resistance. Contrary to pilocarpine alone, the combination of moxonidine (20nmol/1μl) and pilocarpine injected i.c.v. Increased SSG vascular resistance, an effect abolished by the pre-treatment with the α2-adrenoceptor antagonist yohimbine (320nmol/2μl). The increase in arterial pressure, heart rate and mesenteric resistance was not modified by the combination of moxonidine and pilocarpine i.c.v. CONCLUSION: These results suggest that the activation of central α2-adrenoceptors may oppose to the effects of central cholinergic receptor activation in the SSG vascular resistance.
OBJECTIVE: Peripheral treatment with the cholinergic agonist pilocarpine increases salivary gland blood flow and induces intense salivation that is reduced by the central injection of moxonidine (α2-adrenoceptors/imidazoline agonist). In the present study, we investigated the effects of the intracerebroventricular (i.c.v.) injection of pilocarpine alone or combined with moxonidine also injected i.c.v. On submandibular/sublingual gland (SSG) vascular resistance. In addition, the effects of these treatments on arterial pressure, heart rate and on mesenteric and hindlimb vascular resistance were also tested. DESIGN: Male Holtzman rats with stainless steel cannula implanted into lateral ventricle and anaesthetized with urethane+α-chloralose were used. RESULTS:Pilocarpine (500nmol/1μl) injected i.c.v. Reduced SSG vascular resistance and increased arterial pressure, heart rate and mesenteric vascular resistance. Contrary to pilocarpine alone, the combination of moxonidine (20nmol/1μl) and pilocarpine injected i.c.v. Increased SSG vascular resistance, an effect abolished by the pre-treatment with the α2-adrenoceptor antagonist yohimbine (320nmol/2μl). The increase in arterial pressure, heart rate and mesenteric resistance was not modified by the combination of moxonidine and pilocarpine i.c.v. CONCLUSION: These results suggest that the activation of central α2-adrenoceptors may oppose to the effects of central cholinergic receptor activation in the SSG vascular resistance.