RETURNChanges in Acetylcholine Concentrations, Muscarinic Receptors and Contraction Response Rate to Carbachol in the Rabbit Urinary Bladder during the Maturation Period
Hiromi Sanematsu
Department of Urology, Faculty of Medicine, Tottori University, Yonago 683, Japan
In order to clarify developmental changes of the parasympathetic nervous system in the urinary bladder, acetylcholine (ACh) concentrations and number of muscarinic binding sites in the urinary bladder body and the base of 8-, 11-, 18- and 25-week-old rabbits were investigated through HPLC and radioligand binding technique using [3H]-quinuclidinyl benzilate, respectively. The response of the muscle strips to muscarinic agonist, carbachol, were also examined. There were not detectable changes in bladder ACh concentrations during the maturation period (average, 75 ± 12 pmol/mg protein). Although there were double the number of muscarinic binding sites in the bladder body (139 ± 21 fmol/mg protein) compared with the base (71 ± 15 fmol/mg protein), no significant alterations in the number of binding sites were observed during the maturation period. However, the muscle strips of 25-week-old rabbits showed a significant decrease (by 54%, 44% and 44%) in the maximal contractile response to carbachol, although there were no significant changes in the response when half the maximum concentrations of the drug were used, when compared with the response in 8-, 11- and 18-week-old rabbits. These data suggest that the efficiency of the muscarinic signal transduction system of the urinary bladder may be reduced to regulate overgrown muscle contractility during the maturation period.
Key words: acetylcholine concentration; maturation; muscarinic receptor; muscle contraction; urinary bladder