Involvement of a glibenclamide‐sensitive mechanism in the nitrergic neurotransmission of the pig intravesical ureter
- 10 February 1997
- journal article
- research article
- Published by Wiley in British Journal of Pharmacology
- Vol. 120 (4), 609-616
- https://doi.org/10.1038/sj.bjp.0700952
Abstract
1. The present study was designed to investigate whether potassium (K+) channels are involved in the relaxations to nitric oxide (NO) of pig intravesical ureteral preparations suspended in organ baths for isometric tension recordings. In ureteral strips treated with guanethidine (10(-5) M) and atropine (10(-7) M) to block adrenergic neurotransmission and muscarinic receptors, respectively, NO was either released from nitrergic nerves by electrical field stimulation (EFS, 0.5-10 Hz., 1 ms duration, 20 s trains), or exogenously-applied as an acidified solution of sodium nitrite (NaNO2, 10(-6)-10(-3) M). 2. Incubation with an inhibitor of guanylate cyclase activation by NO, methylene blue (10(-5) M) did not change the basal tension of intravesical ureteral strips but inhibited the relaxation induced by EFS or exogenous NO on ureteral preparations contracted with the thromboxane analogue U46619 (10(-7) M). 3. Incubation with charybdotoxin (3 x 10(-8) M) and apamin (5 x 10(-7) M), which are inhibitors of large and small conductance calcium (Ca2+)-activated K+ channels, respectively, did not modify basal tension or the relaxations induced by EFS and exogenous NO. Treatment with charybdotoxin or apamin plus methylene blue (10(-5) M) significantly reduced the relaxations to EFS and exogenous NO. However, in both cases the reductions were similar to the inhibition evoked by methylene blue alone. The combined addition of charybdotoxin plus apamin did not change the relaxations to EFS or exogenously added NO of the porcine intravesical ureter. 4. Cromakalim (10(-8) 3 x 10(-6) M), an opener of ATP-sensitive K+ channels, evoked a dose-dependent relaxation with a pD2 of 7.3 +/- 0.2 and maximum relaxant effect of a 71.8 +/- 4.2% of the contraction induced by U46619 in the pig intravesical ureter. The blocker of ATP-sensitive K+ channels, glibenclamide (10(-6) M), inhibited markedly the relaxations to cromakalim. 5. Glibenclamide (10(-6) M) had no effect on the basal tone of ureteral preparations but significantly reduced the relaxations induced by both EFS and exogenous NO. Combined treatment with methylene blue (10(-5) M) and glibenclamide (10(-6) M) did not exert an effect greater than that of methylene blue alone on either EFS- or NO-evoked relaxations of the pig ureter. 6. The present results suggest that NO acts as an inhibitory neurotransmitter in the pig intravesical ureter and relaxes smooth muscle through a guanylate cyclase-dependent mechanism which seems to favour the opening of glibenclamide-sensitive K+ channels.Keywords
This publication has 39 references indexed in Scilit:
- Nitric Oxide Inhibits Contraction of Isolated Pig Ureteral Smooth MuscleJournal of Urology, 1996
- Role of cyclic AMP and protein kinase A in K+ channel activation by calcitonin gene‐related peptide (CGRP) in the guinea‐pig ureterJournal of Autonomic Pharmacology, 1995
- Muscarinic binding sites of the pig intravesical ureterJournal of Autonomic Pharmacology, 1995
- Histochemical and functional evidence for a cholinergic innervation of the equine ureterJournal of the Autonomic Nervous System, 1994
- Effect of Cromakalim and Pinacidil on 86Rb Efflux from Guinea Pig Urinary Bladder Smooth MusclePharmacology, 1994
- Mediation of contraction by cholinergic muscarinic receptors in the ureterovesical junctionJournal of Autonomic Pharmacology, 1992
- Mediation of contraction and relaxation by alpha- and beta-adrenoceptors in the ureterovesical junction of the sheepResearch in Veterinary Science, 1992
- Nitric oxide, a novel neuronal messengerNeuron, 1992
- Localization of nitric oxide synthase indicating a neural role for nitric oxideNature, 1990
- The Effects of Cromakalim on the Detrusor Muscle of Human and Pig Urinary BladderBritish Journal of Urology, 1989