Influence of relaxin on the neurally induced relaxant responses of the mouse gastric fundus.
The peptide hormone relaxin has been reported to depress the amplitude of contractile responses in the mouse gastric fundus by upregulating nitric oxide (NO) biosynthesis at the neural level. In the present study, we investigated whether relaxin also influenced nonadrenergic, noncholinergic (NANC) gastric relaxant responses in mice. Female mice in proestrus or estrus were treated for 18 h with relaxin (1 microg s.c.) or vehicle (controls). Mechanical responses of gastric fundal strips were recorded via force-displacement transducers. In carbachol precontracted strips from control mice and in the presence of guanethidine, electrical field stimulation (EFS) elicited fast relaxant responses that may be followed by a sustained relaxation. All relaxant responses were abolished by tetrodotoxin. Relaxin increased the amplitude of the EFS-induced fast relaxation without affecting either the sustained one or the direct smooth muscle response to papaverine. In the presence of the NO synthesis inhibitor L-N(G)-nitro arginine (L-NNA), that abolished the EFS-induced fast relaxation without influencing the sustained one, relaxin was ineffective. In strips from relaxin-pretreated mice, EFS-induced fast relaxations were enhanced in amplitude with respect to the controls, while sustained ones as well as direct smooth muscle responses to papaverine were not changed. Further addition of relaxin to the bath medium did not influence neurally induced fast relaxant responses, whereas L-NNA did. In conclusion, in the mouse gastric fundus, relaxin enhances the neurally induced nitrergic relaxant responses acting at the neural level.
Baccari
Maria Caterina
MC
Department of Physiological Sciences, University of Florence, Florence, Italy. mcaterina.baccari@unifi.it
Bani
Daniele
D
Bigazzi
Mario
M
Calamai
Franco
F
D018663:Adrenergic Agents / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D030762:Estrous Cycle / Q000502:physiology; D005260:Female; D005748:Gastric Fundus / Q000201:enzymology / Q000502:physiology*; D006145:Guanethidine / Q000494:pharmacology; D051379:Mice; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000502:physiology*; D009569:Nitric Oxide / Q000502:physiology*; D019335:Nitroarginine / Q000494:pharmacology; D012065:Relaxin / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*
D018663:Adrenergic Agents; D018679:Cholinergic Agonists; D004791:Enzyme Inhibitors; D019335:Nitroarginine; D009569:Nitric Oxide; D002217:Carbachol; D012065:Relaxin; D006145:Guanethidine