The inhibitory effect of nociceptin on the micturition reflex in anaesthetized rats |
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Authors: | Sandro Giuliani Alessandro Lecci Manuela Tramontana Carlo Alberto Maggi |
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Institution: | 1.Department of Pharmacology, Menarini Ricerche, via Rismondo 12A, 50131 Florence, Italy |
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Abstract: | - We have investigated the effect of nociceptin on the micturition reflex evoked by distension or topical application of capsaicin on the urinary bladder of urethane-anaesthetized rats.
- Nociceptin produced a dose-dependent (3–100 nmol kg−1 i.v.) transient suppression of the distension-evoked micturition reflex: its effect was not modified by guanethidine (68 μmol kg−1 s.c.) nor by bilateral cervical vagotomy, alone or in combination, and by naloxone (1.2 μmol kg−1 i.v.).
- Nociceptin (100 nmol/kg i.v.) slightly (about 30%) inhibited the contractions of the rat bladder produced by pre- or postganglionic electrical stimulation of the pelvic nerve.
- Nociceptin almost totally abolished the reflex component of the response to topical capsaicin (1 μg in 50 μl).
- In the rat isolated bladder, submaximal contractions produced by electrical field stimulation were slightly reduced (25±4% inhibition) by 1 μM nociceptin. Nociceptin did not affect the contraction of the rat bladder induced by acetylcholine (10 μM) or ATP (1 mM).
- These findings indicate that nociceptin exerts a naloxone-resistant suppression of the volume-evoked micturition reflex which involves inhibition of transmitter release from postganglionic bladder nerves. An inhibitory effect on bladder afferent nerves is also suggested.
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Keywords: | Nociceptin micturition reflex urinary bladder pelvic stimulation |
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