[Biochemical and functional characteristics of autonomic receptors in neonatal urinary tract smooth muscle].

I investigated the biochemical (Bmax, KD) and functional (contractile force) characteristics of autonomic receptors in the 1-day-old rabbit urinary tract smooth muscle, and compared the data obtained to those already reported in adult rabbits. The rank order of the receptor densities in neonatal rabbits are dome greater than base greater than urethra greater than ureter for alpha 1 (3H-PZ), ureter greater than urethra greater than base greater than dome for alpha 2 (3H-YOH), dome greater than base greater than urethra greater than ureter for beta (3H-DHA) and dome greater than base greater than urethra greater than ureter for muscarinic (3H-QNB). Unlike the findings in the adult rabbit, there is a much larger number of functional muscarinic receptors in the bladder dome and a much smaller number of functional alpha 1-receptors in the urethra of neonatal rabbits. The differences observed in the pattern of distribution of these receptors between neonatal and adult urinary tracts may play a determinant role in the physiological development of the urinary system.