ABSTRACT
Previous work in this laboratory has demonstrated that the bladders of 1-day-old and 1-week-old rabbits generate higher pressures in whole-bladder preparations than bladders from mature 8-week-old rabbits. In addition, the density of cholinergic receptors does not change during this maturation period. The present study was designed to determine if the increased responsiveness of the neonatal bladder was specific for cholinergic stimulation. Using bladder strips, we have demonstrated that the newborn bladders generated much greater tension in response to ATP, serotonin, histamine, and substance P. The response of the 1-day-old bladder smooth muscle to these contractile agents was at least double the response of the 8-week-old bladders. However, the response of all age groups to bethanechol was approximately the same, and the response to KCl was only 40% greater in the 1-day-old bladders as compared to the adult. These current studies indicate that the newborn bladder responds to a variety of nonadrenergic, noncholinergic agonists to a significantly higher degree than the adult bladder, and that maturation is accompanied by substantial changes in the pharmacology of the bladder.
Subject(s)
Muscle Contraction/drug effects , Urinary Bladder/drug effects , Adenosine Triphosphate/pharmacology , Age Factors , Animals , Animals, Newborn/growth & development , Bethanechol , Bethanechol Compounds/pharmacology , Dose-Response Relationship, Drug , Histamine/pharmacology , Rabbits , Serotonin/pharmacology , Substance P/pharmacology , Urinary Bladder/growth & developmentABSTRACT
Recent advances in imaging technology have allowed for the diagnosis of many congenital urologic abnormalities through the use of antenatal ultrasonography. There is controversy in the literature as to whether antenatally detected dilatations of the urinary tract are always secondary to obstruction or if in select cases the dilatations are physiologic in nature and will spontaneously regress. Benign dilatations of the fetal urinary tract are postulated to be secondary to the increased fetal diuresis and a more compliant fetal urinary tract. No one has investigated the possibility that such dilatations might be a consequence of the hormonal changes seen with pregnancy. In this study we present evidence for a change in bladder function with pregnancy. A summary of our results shows that in the presence of bethanechol, strips from the urinary bladders of pregnant rabbits generate 50% less tension in response to calcium than those from nonpregnant rabbits. Such a suppression in smooth muscle function might also help explain the benign dilatations of the upper urinary tract which are seen frequently during pregnancy.