Reflex adrenergic inhibition of colonic motility in anesthetized rat caused by nociceptive stimuli of peritoneum. An alpha 2-adrenoceptor-mediated response.
Nociceptive stimulation of the peritoneum inhibits colonic motility via a sympathoadrenergic reflex. This sympathetic reflex most probably induces the inhibition indirectly via a presynaptic blockade of cholinergic transmission. To further clarify this reflex, colonic motility was continuously recorded by a volume method in rats exposed to nociceptive abdominal stimulation and intravenous drug administration. Intraabdominally applied HCl inhibited colonic motility, which was unaffected by nonselective beta-adrenoceptor blockade (propranolol). However, the nonselective alpha-adrenoceptor antagonist phentolamine and the selective alpha 2-adrenoceptor antagonist yohimbine restored motility. Spontaneous colonic motility was unaffected by the nonselective beta-adrenoceptor agonist (isoproterenol) and the selective alpha 1-adrenoceptor agonist (L-phenylephrine). On the other hand, a nonselective alpha-agonist (noradrenaline) and a selective alpha 2-adrenoceptor agonist (clonidine) inhibited spontaneous colonic motility. It is suggested that in the rat sympathetic reflex inhibition of colonic motility caused by abdominal nociception is mediated via presynaptic alpha 2-adrenoceptors inhibiting the excitatory cholinergic neurons.
Sjöqvist
A
A
Hallerbäck
B
B
Glise
H
H
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003106:Colon / Q000294:innervation / Q000502:physiology*; D005260:Female; D005769:Gastrointestinal Motility / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology*; D010538:Peritonitis / Q000139:chemically induced / Q000503:physiopathology; D010646:Phentolamine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology; D012018:Reflex / Q000187:drug effects; D015016:Yohimbine / Q000494:pharmacology
D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D010656:Phenylephrine; D015016:Yohimbine; D011433:Propranolol; D007545:Isoproterenol; D010646:Phentolamine