ABSTRACT
PURPOSE: The location of acetylcholinesterase-containing nerve fibers suggests a role for acetylcholine in both contractility and secretion in the prostate gland. The colocalization of nitrergic nerves with cholinergic nerves, and the cotransmission of nitric oxide with acetylcholine in cholinergic nerves, has been demonstrated in the prostate glands of various species. Thus, we investigated the effects of acetylcholine on phenylephrine-induced contraction and the correlation between cholinergic transmission and nitric oxide synthase by using isolated prostate strips of rabbits. MATERIALS AND METHODS: Isolated prostate strips were contracted with phenylephrine and then treated with cumulative concentrations of acetylcholine. Changes in acetylcholine-induced relaxation after preincubation with NG-nitroarginine methyl ester, 7-nitroindazole, and aminoguanidine were measured. The effects of selective muscarinic receptor antagonists were also evaluated. RESULTS: In the longitudinal phenylephrine-contracted strip, the cumulative application of acetylcholine (10(-9) to 10(-4) M) elicited a concentration-dependent relaxation effect. Acetylcholine-induced relaxation was inhibited not only by nitric oxide synthase inhibitors (10 microM L-NAME or 10 microM 7-nitroindazole) but also by 10 microM atropine and some selective muscarinic receptor antagonists (10(-6) M 11-([2-[(diethylamino)methyl]-1-piperdinyl]acetyl)-5,11-dihydro-6H-pyrido[2,3-b][1,4]benzodiazepine-6-one and 10(-6) M 4-diphenylacetoxy-N-methyl-piperidine). In contrast, relaxation was significantly increased by pretreatment of the strips with 10 mM L-arginine. CONCLUSIONS: Acetylcholine relaxed phenylephrine-induced contractions of isolated rabbit prostate strips. This relaxation may be mediated via both cholinergic and constitutive nitric oxide synthase with both the M2 and M3 receptors possibly playing key roles.
Subject(s)
Acetylcholine , Atropine , Contracts , Guanidines , Indazoles , Nerve Fibers , Neurons , NG-Nitroarginine Methyl Ester , Nitrergic Neurons , Nitric Oxide , Nitric Oxide Synthase , Nitric Oxide Synthase Type I , Phenylephrine , Prostate , Receptor, Muscarinic M2 , Receptor, Muscarinic M3 , Receptors, Muscarinic , RelaxationABSTRACT
Objective To explore the mechanism of ZMS regulation of M_2 muscarinic receptor mRNA expression. Methods In vitro cultured CHOm2 cells were divided into ZMS 1 group (treatment with 1 × 10~(-5) mol/L ZMS for 24 h), ZMS 2 group (treatment with 1 × 10~(-5) mol/L ZMS for 24 h and 1 μg/mL cycloheximide for 12 h) and ZMS 3 group (treatment with 1 μg/mL cycloheximide for 4 h and 1 × 10 ~(-5) mol/L ZMS for 24 h), and their corresponding control groups were also established (substitution of ZMS by DMSO). Actinomycin D was added to cultured CHOm2 cells of each group to inhibit the synthesis of mRNA. CHOm2 cell samples were taken at different time points, the relative expression of M_2 receptor mRNA was detected by Real-time PCR, and half life of M_2 receptor mRNA was calculated. Results Compared with corresponding control groups, the half life of M_2 receptor mRNA of CHOm2 cells in ZMS 1 group and ZMS 2 group was significantly prolonged [(4.75h± 0.54) h vs (2.13 ±0.23) h, P<0.05; (5.43 ±1.13) h vs (2.46 ±0.09) h, P<0.05]. There was no significant difference in half life of M_2 receptor mRNA of CHOm2 cells between ZMS 3 group and its corresponding control [ ( 3.06 ±0.23) h vs (3.00 ± 0.20) h, P > 0.05]. Conclusion De novo protein synthesis is required for the enhancement of M_2 receptor mRNA stability regulated by ZMS.