Maturation of stretch-induced contractile activity and its muscarinic regulation in isolated whole bladder strips from rat.
OBJECTIVE
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.
Gevaert
Thomas
T
Department of Urology, University Hospitals Gasthuisberg, Katholieke Universiteit Leuven, Leuven, Belgium. thomas.gevaert@med.kuleuven.ac.be
Owsianik
Grzegorz
G
Hutchings
Graham
G
Everaerts
Wouter
W
Nilius
Bernd
B
De Ridder
Dirk
D
D000818:Animals; D005260:Female; D066298:In Vitro Techniques; D009119:Muscle Contraction; D051381:Rats; D017208:Rats, Wistar; D011976:Receptors, Muscarinic / Q000502:physiology*; D001743:Urinary Bladder / Q000502:physiology*
D011976:Receptors, Muscarinic