Premium
Bladder distension and activation of the efferent function of sensory fibres: similarities with the effect of capsaicin
Author(s) -
Lecci A,
Giuliani S,
Tramontana M,
Santicioli P,
Criscuoli M,
Dion S,
Maggi C A
Publication year - 1998
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0701820
Subject(s) - distension , isoprenaline , endocrinology , chemistry , medicine , anesthesia , stimulation
The effects of the tachykinin NK 2 receptor antagonist MEN 11420 (100 nmol kg −1 , i.v.) and isoprenaline (400 nmol kg −1 , i.v.) were compared in a model of distension‐induced bladder activity in isovolumetric conditions. MEN 11420 induced a relaxation of the basal tone of the urinary bladder that was dependent on the volume of the viscus: the effect was absent at low volumes (0.2 and 0.5 ml) and it was maximal at high volumes of distension (1 and 2 ml), approaching about 60% of the isoprenaline‐induced relaxation. The relaxant effect of isoprenaline was always evident at all volumes of distension. Tetrodotoxin (1–100 μ M , intravesically applied) abolished distension‐evoked micturition contractions, but did not prevent the relaxant effect of MEN 11420‐ or isoprenaline on the bladder tone. The cyclo‐oxygenase inhibitor S‐ketoprofen (0.5 μmol kg −1 , i.v.) produced a marked decrease of the bladder tone and a concomitant reduction of bladder motility at 1 ml volume of distension. At 2 ml of distension, S‐ketoprofen still decreased the minimal pressure but had no significant effect on other parameters of vesical motility. In S‐ketoprofen‐pretreated rats, the relaxant effect of MEN 11420 was significant at 2 but not at 1 ml of distension, and that of isoprenaline was reduced by 50% at both 1 and 2 ml. Ruthenium red (10 μmol kg −1 , i.v.) had no effect at a low volume of distension (0.2 ml) or at highest volume (2 ml) but decreased the basal tone and the frequency of bladder contractions at 1 ml of distension. In ruthenium red‐pretreated rats, MEN 11420 failed to decrease bladder tone at 1 ml, whereas at 2 ml the effect of MEN 11420 was not different from that observed in controls (43 vs 60% of isoprenaline‐induced relaxation, respectively). At both 1 and 2 ml of distension, capsaicin pretreatment (164 μmol kg −1 , s.c. 5 days before) reduced the frequency of micturition contractions but had no effect on the bladder tone. Capsaicin pretreatment prevented the relaxant effect of MEN 11420 on the bladder tone both at 1 and at 2 ml of distension. It is concluded that the release of tachykinins from capsaicin‐sensitive afferent nerves induced by bladder distension is resistant to tetrodotoxin and to prostaglandin synthesis inhibition. Tachykinins modulate the vesical tone by acting through NK 2 receptors.