Role of nicotinic acetylcholine receptor subtypes on nicotine's enhancing effect on electrical field stimulation elicited contractile responses in rabbit urine bladder

• Published in: European review for medical and pharmacological sciences Vol. 20; no. 8; p. 1636
• Main Authors: Ozturk Fincan, G S, Vural, I M, Yildirim, S S, Isli, F, Dilekoz, E, Ercan, S, Sarioglu, Y
• Format: Journal Article
• Language: English
• Published: Italy 01.04.2016
• Subjects: Animals; Electric Stimulation; In Vitro Techniques; Muscle Contraction - drug effects; Muscle, Smooth - drug effects; Nicotine - pharmacology; Rabbits; Receptors, Nicotinic; Urinary Bladder - drug effects
• ISSN: 2284-0729

This study aims to investigate the contribution of presynaptic nicotinic acetylcholine receptors (nAChRs) sub-types to nicotine-induced enhancement in electrical field stimulation (EFS) EFS-mediated contractile responses in rabbit urine bladder smooth muscle preparations. Rabbit urine bladder smooth muscle strips were placed in organ baths containing 20 ml of an aerated Krebs-Henseleit solution, and contractions were recorded using isometric force displacement transducers. Following the acquisition of control EFS (60 V, 8 Hz, 1 ms) responses, nicotine was added to the bath at a 3×10-5 M concentration, and EFS responses were obtained. The effect of nAChR antagonists on nicotine-induced augmentation in EFS-mediated responses was investigated in the presence of hexamethonium, dihydro-β-erythroidine, mecamylamine, and α-bungarotoxin. Tetrodotoxin (TTX; 10-6 M) completely blocked EFS-induced contractile responses in smooth muscle strips. Similarly, Atropine (10-6 M), when administered with α,β-methylene adenosine triphosphate (α,β-methylene-ATP) (10-5 M), completely blocked EFS responses. Nicotine significantly enhanced EFS-mediated contractile responses (23.67% ± 1.75). Nicotine-induced increases in EFS responses were largely inhibited by hexamethonium, mecamylamine, and dihydro-β-erythroidine, whereas α-bungarotoxin only partly inhibited these enhancements. These findings demonstrate that EFS-induced neurogenic contractions in rabbit urine bladder smooth muscle strips are mediated by purinergic and cholinergic transmissions, and the α4β2, α3β4, and α7 sub-types of nAChRs contribute to the enhancement effect of nicotine on EFS-induced contractile responses.