Detrusor contraction--Focus on muscarinic receptors.
Stimulation of muscarinic receptors is a main mechanism for contractile activation of the detrusor from both animals and humans. Muscarinic receptors are coupled to G-proteins, but the signal transduction systems may vary. In general, M, M and M receptors are considered to couple preferentially to Gq/11, activating phosphoinositide hydrolysis, in turn leading to mobilization of intracellular calcium through inositol trisphosphate generation. M2 and M4 receptors couple to pertussis toxin-sensitive Gi/o, resulting in inhibition of adenylyl cyclase activity. However, in the detrusor smooth muscle, other signalling pathways may be involved. Recent investigations revealed that a main pathway for muscarinic receptor activation of the detrusor may be calcium influx via L-type calcium channels, and increased sensitivity to calcium of the contractile machinery via inhibition of myosin light chain phosphatase through activation of Rho-kinase. The importance of these findings for treatment of voiding dysfunction remains to be established.
Andersson
Karl-Erik
KE
Department of Clinical and Experimental Pharmacology, Lund University Hospital, Lund, Sweden. Karl-Erik.Andersson@klinifarm.lu.se
D000818:Animals; D006801:Humans; D009119:Muscle Contraction / Q000502:physiology*; D009130:Muscle, Smooth / Q000502:physiology*; D011976:Receptors, Muscarinic / Q000502:physiology*; D001743:Urinary Bladder / Q000502:physiology*
D011976:Receptors, Muscarinic