Long-term nitric oxide deficiency causes muscarinic supersensitivity and reduces beta(3)-adrenoceptor-mediated relaxation, causing rat detrusor overactivity.
OBJECTIVE
Overactive bladder is a complex and widely prevalent condition, but little is known about its physiopathology. We have carried out morphological, biochemical and functional assays to investigate the effects of long-term nitric oxide (NO) deficiency on muscarinic receptor and beta-adrenoceptor modulation leading to overactivity of rat detrusor muscle.


METHODS
Male Wistar rats received N(omega)-nitro-L-arginine methyl ester (L-NAME) in drinking water for 7-30 days. Functional responses to muscarinic and beta-adrenoceptor agonists were measured in detrusor smooth muscle (DSM) strips in Krebs-Henseleit solution. Measurements of [(3)H]inositol phosphate, NO synthase (NOS) activity, [(3)H]quinuclidinyl benzilate ([(3)H]QNB) binding and bladder morphology were also performed.


RESULTS
Long-term L-NAME treatment significantly increased carbachol-induced DSM contractile responses after 15 and 30 days; relaxing responses to the beta(3)-adrenoceptor agonist BRL 37-344 were significantly reduced at 30 days. Constitutive NOS activity in bladder was reduced by 86% after 7 days and maintained up to 30 days of L-NAME treatment. Carbachol increased sixfold the [(3)H]inositol phosphate in bladder tissue from rats treated with L-NAME. [(3)H]QNB was bound with an apparent K(D) twofold higher in bladder membranes after L-NAME treatment compared with that in control. No morphological alterations in DSM were found.


CONCLUSIONS
Long-term NO deficiency increased rat DSM contractile responses to a muscarinic agonist, accompanied by significantly enhanced K(D) values for muscarinic receptors and [(3)H]inositol phosphate accumulation in bladder. This supersensitivity for muscarinic agonists along with reductions of beta(3)-adrenoceptor-mediated relaxations indicated that overactive DSM resulted from chronic NO deficiency.
Mónica
F Z T
FZ
Department of Pharmacology, Faculty of Medical Sciences, State University of Campinas (UNICAMP), Campinas, São Paulo, Brazil.
Bricola
A A O
AA
Báu
F R
FR
Freitas
L L Lopes
LL
Teixeira
S A
SA
Muscará
M N
MN
Abdalla
F M F
FM
Porto
C S
CS
De Nucci
G
G
Zanesco
A
A
Antunes
E
E
D058667:Adrenergic beta-3 Receptor Agonists; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D007295:Inositol Phosphates / Q000378:metabolism; D008297:Male; D018721:Muscarinic Agonists / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000378:metabolism; D019331:NG-Nitroarginine Methyl Ester; D009569:Nitric Oxide / Q000172:deficiency*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D022702:Receptors, Adrenergic, beta-3 / Q000378:metabolism*; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000378:metabolism*; D001743:Urinary Bladder / Q000378:metabolism / Q000503:physiopathology; D053201:Urinary Bladder, Overactive / Q000503:physiopathology*
D058667:Adrenergic beta-3 Receptor Agonists; D000318:Adrenergic beta-Agonists; D007295:Inositol Phosphates; D018721:Muscarinic Agonists; D022702:Receptors, Adrenergic, beta-3; D011976:Receptors, Muscarinic; D009569:Nitric Oxide; D002217:Carbachol; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester