Prejunctional M1 facilitory and M2 inhibitory muscarinic receptors mediate rat bladder contractility.
Subtype-selective muscarinic antagonists effects on carbachol-induced and electric field-stimulated contractility of rat bladder were compared in vitro. Schild plot analysis of cumulative carbachol dose-response curves in the presence of antagonists was consistent with M3-mediated bladder contractions. However, nerve-evoked contractions were inhibited 15% at 30 Hz (P < 0.01) by 10 nM pirenzepine (M1-selective antagonist), whereas 10 nM methoctramine (M2-selective antagonist) increased these contractions by 17% at 30 Hz (P < 0.01). Identical doses had no effect on carbachol-induced contractions, indicating prejunctional M1 facilitory and M2 inhibitory receptors. m1 Receptors could not be identified by subtype-selective antibodies, nor could the m1 transcript be identified by Northern hybridization. However, m1, m2, m3, and m4 transcripts were identified in rat bladder using the reverse transcriptase-polymerase chain reaction, providing support for the existence of the m1 subtype. In conclusion, strong evidence is provided for the existence of prejunctional M1 facilitory and M2 inhibitory and postjunctional M3 receptors modulating contractility in the rat urinary bladder.
Braverman
A S
AS
Department of Urology, Temple University School of Medicine, Philadelphia 19140, USA.
Kohn
I J
IJ
Luthin
G R
GR
Ruggieri
M R
MR
D000818:Animals; D015152:Blotting, Northern; D002217:Carbachol / Q000494:pharmacology; D004558:Electric Stimulation; D008297:Male; D018721:Muscarinic Agonists / Q000494:pharmacology; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D012194:RNA-Directed DNA Polymerase; D051381:Rats; D017207:Rats, Sprague-Dawley; D011976:Receptors, Muscarinic / Q000235:genetics / Q000502:physiology*; D001743:Urinary Bladder / Q000502:physiology*
D018721:Muscarinic Agonists; D018727:Muscarinic Antagonists; D012333:RNA, Messenger; D011976:Receptors, Muscarinic; D002217:Carbachol; D012194:RNA-Directed DNA Polymerase