Are m-cholinoceptors of guinea pig gallbladder smooth muscle of m4 subtype?
The antagonism of carbachol-induced contractions of guinea pig gallbladder smooth muscle strips via selective antagonists, methoctramine, HHSiD, pf-HHSiD and DABDMA has been investigated in order to find out the m-cholinoceptor subtype(s) of gallbladder smooth muscle. All m-cholinoceptor antagonists examined, displaced the concentration-response curves to the right parallel in a concentration-dependent manner without affecting the maximum response. Schild analysis of data was consistent with competitive antagonism. -log KB values of the antagonists were 7.37 for HHSiD, 7.53 for pf-HHSiD, 6.58 for DABDMA and 7.60 for methoctramine. These results, together with the high affinity of pirenzepine and low affinities of 4-DAMP and AF-DX 116, indicate that the m-cholinoceptors of the guinea pig gallbladder which mediate cholinergic contractions are not of m1-, m2- and m3- subtypes but seem likely to be of m4-subtype.
Department of Physiology, Marmara University, School of Medicine, Istanbul, Turkey.
U
U
Ozkutlu
I
I
Alican
F
F
Karahan
F
F
Onat
B C
BC
Yegen
N B
NB
Ulusoy
S
S
Oktay
D000818:Animals; D002217:Carbachol / Q000037:antagonists & inhibitors; D018680:Cholinergic Antagonists; D005260:Female; D005704:Gallbladder / Q000187:drug effects; D006168:Guinea Pigs; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D010276:Parasympatholytics / Q000494:pharmacology*; D011950:Receptors, Cholinergic / Q000145:classification*
D018680:Cholinergic Antagonists; D010276:Parasympatholytics; D011950:Receptors, Cholinergic; D002217:Carbachol