Enhancement effects of nicotine on neurogenic relaxation responses in the corpus cavernosum in rabbits: the role of nicotinic acetylcholine receptor subtypes.
Nicotine acts as an agonist of nicotinic acetylcholine receptors, which belong to a superfamily of neurotransmitter-gated ion channels. We previously demonstrated that nicotine increases the electrical field stimulation (EFS)-evoked nitrergic relaxation responses via activation of nicotinic acetylcholine receptors. The aim of the present study is to investigate the subtypes of nicotinic acetylcholine receptors in rabbit corpus cavernosum. EFS-evoked relaxation responses were recorded from corpus cavernosum strips obtained from rabbits with an isometric force displacement transducers. Effects of nicotine on EFS-evoked relaxations were examined in pre-contracted tissues. Then the effect of nicotine on the EFS-evoked relaxations was examined in the presence of hexamethonium, dihydro-beta-erythroidine, mecamylamine or alpha-bungarotoxin. In our study, nicotine (3 x 10(-5), 10(-4)) transiently increased nitrergic relaxations induced by EFS in the rabbit isolated corpus cavernosum. While hexamethonium and mecamylamine near totally inhibited or abolished the neurorelaxation response to nicotine (3 x 10(-5)) on EFS, dihydro-beta-erythroidine and alpha-bungarotoxin partially inhibited these responses. These findings demonstrated that the alpha3-beta4, alpha4-beta2 and alpha7 subunits of nicotinic acetylcholine receptors play role on the nicotine-induced augmentation in EFS-evoked relaxation responses in rabbit corpus cavernosum.
Ozturk Fincan
Gokce Sevim
GS
Department of Pharmacology, Medical School, Gazi University, Ankara, Turkey.
Vural
Ismail Mert
IM
Ercan
Zeynep Sevim
ZS
Sarioglu
Yusuf
Y
D000818:Animals; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects*; D009538:Nicotine / Q000494:pharmacology*; D018733:Nicotinic Antagonists / Q000494:pharmacology; D010413:Penis / Q000187:drug effects / Q000294:innervation* / Q000502:physiology*; D021122:Protein Subunits / Q000378:metabolism*; D011817:Rabbits; D011978:Receptors, Nicotinic / Q000378:metabolism*; D013997:Time Factors
D018733:Nicotinic Antagonists; D021122:Protein Subunits; D011978:Receptors, Nicotinic; D009538:Nicotine