Aim: Besides the establishment of neural reflex pathways, developmental changes in local bladder properties probably also contribute to the onset of mature voiding reflexes. Here we explored the behavior of stretch-induced contractile activity (SIC) and its muscarinic regulation in neonatal and adult rat bladders.
Methods: SIC was studied in bladder strips from D0, D7, D28 rat pups and adult rats (15 weeks). The responses to a non-selective [Carbachol (CA), 10(-8.5)-10(-6) M] and an M(2)-selective muscarinic agonist [arecaidine but-2-ynyl ester tosylate (ABET), 10(-9.5)-10(-7) M] were studied. The expression of M(2) and M(3) mRNA was investigated using quantitative PCR in whole bladders. The response of SIC to KCl (50 mM) and to the non-adrenergic non-cholinergic (NANC) drugs Substance P (1 microM) and alpha,beta-Methyleneadenosine 5'-triphosphate lithium salt (MATP) (1 microM) were also studied.
Results: We found evidence for an enhanced response to the muscarinic agonists CA and ABET in neonatal bladders. This might be due to the onset of a direct contractile role for M(2), given the moderate M(2)-properties of ABET and the absence of ABET-effects on adult bladder strips. Further data showed an increased expression of both M(2) and M(3) at the mRNA level and a changed response of SIC to NANC drugs in neonatal bladder.
Conclusions: This study reveals a changed response of SIC to muscarinic and NANC drugs in neonatal rat bladder together with changes at the muscarinic mRNA level, which might all contribute to a better insight in the role of SIC in the onset of mature voiding.
(c) 2010 Wiley-Liss, Inc.