Difference between the antisecretory mechanisms of opioids and the somatostatin analogue octreotide in cholera toxin-induced small intestinal secretion in the rat.
The antisecretory effect of morphine and the somatostatin analogue octreotide was studied on cholera toxin-induced secretion in anaesthetized rats. Small intestinal secretion was induced with cholera toxin. Morphine (6 mg/kg b.wt.) and the somatostatin analogue octreotide (3 micrograms/kg b.wt.) reduced the cholera secretion in rats whose intestines had been subjected to sympathetic denervation. This was in contrast to the secretion elicited by helodermin which was unaffected by octreotide and morphine in the presence of nicotinic ganglionic blockade. The alpha-adrenergic receptor blocker phentolamine (1-2 mg/kg b.wt. i.v.) and the inhibitor of sympathetic transmitter release guanethidine (5 mg/kg b.wt. i.v.) abolished the antisecretory effect of morphine on the cholera secretion in contrast to the antisecretory effect of somatostatin which was unaffected by the alpha-blockade. It is proposed that the antisecretory effect of morphine and octreotide on cholera toxin-induced secretion was conducted at a step prior to the activation of the secretory epithelium and that the antisecretory effect of morphine was mediated indirectly by interaction with sympathetic nerve terminals in the intestine. The findings are consistent with a model where octreotide and morphine inhibit the nervous secreto-motor reflex activated by the cholera toxin.
Sjöqvist
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Department of Physiology, University of Göteborg, Sweden.
D000818:Animals; D002772:Cholera Toxin / Q000633:toxicity; D006145:Guanethidine / Q000494:pharmacology; D036341:Intercellular Signaling Peptides and Proteins; D007413:Intestinal Mucosa / Q000187:drug effects / Q000294:innervation / Q000378:metabolism*; D007421:Intestine, Small / Q000187:drug effects* / Q000294:innervation; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D015282:Octreotide / Q000494:pharmacology*; D010455:Peptides / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000494:pharmacology
D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D012701:Serotonin; D009020:Morphine; C040442:heliodermin; D002772:Cholera Toxin; D015282:Octreotide; D010646:Phentolamine; D006145:Guanethidine