Effects of octreotide on responses to colorectal distension in the rat.
OBJECTIVE
It has been suggested that the analgesic effect of the somatostatin analogue octreotide in visceral pain involves peripheral mechanisms. We evaluated the effect of octreotide on responses to noxious colorectal distension in rats.


METHODS
In a behavioural study, pressor and electromyographic responses to colorectal distension were evaluated before and after intravenous or intrathecal administration of octreotide. In pelvic nerve afferent fibre recordings, responses of mechanosensitive fibres innervating the colon to noxious colorectal distension (80 mm Hg, 30 seconds) were tested before and after octreotide.


RESULTS
Octreotide was ineffective in attenuating responses to colorectal distension in either normal or acetic acid inflamed colon when administered intravenously but attenuated responses when given intrathecally. Administration of octreotide over a broad dose range (0.5 microg/kg to 2.4 mg/kg) did not alter responses of afferent fibres to noxious colorectal distension in untreated, or acetic acid or zymosan treated colons.


CONCLUSIONS
In the rat, octreotide has no peripheral (pelvic nerve) modulatory action in visceral nociception. The antinociceptive effect of octreotide in this model of visceral nociception is mediated by an action at central sites.
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Department of Pharmacology, Bowen Science Building, College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA.
Burton
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MB
Gebhart
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GF
D019342:Acetic Acid; D000704:Analysis of Variance; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004576:Electromyography / Q000187:drug effects; D005765:Gastrointestinal Agents / Q000627:therapeutic use*; D007275:Injections, Intravenous; D007278:Injections, Spinal; D008297:Male; D008532:Megacolon, Toxic / Q000188:drug therapy*; D009619:Nociceptors / Q000187:drug effects; D015282:Octreotide / Q000627:therapeutic use*; D011311:Pressoreceptors / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D018709:Statistics, Nonparametric; D016896:Treatment Outcome
D005765:Gastrointestinal Agents; D019342:Acetic Acid; D015282:Octreotide