Central and peripheral components of dermorphin's effect on rat intestinal propulsion in comparison to morphine |
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Authors: | D Parolaro M Sala G Crema L Spazzi R Cesana E Gori |
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Institution: | Institute of Pharmacology, Faculty of Sciences, University of Milan Via Vanvitelli 32/A, 20129 Milan, Italy |
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Abstract: | Dermorphin, injected intracerebroventricularly (ICV) to rats, provokes, like to morphine, an inhibition of intestinal propulsion linearly related to the log of the administered doses (in the range from 0.06 to 0.56 μg/rat), but it is 143 times more active than morphine. Naloxone, ICV or IP, antagonizes dermorphin less effectively than morphine. Quaternary naloxone ICV administered antagonizes the intestinal effect of ICV dermorphin, while IP administered it is not effective until 8 mg/kg. The dose of dermorphin maximally active by the ICV route (0.56 μg/rat) is completely inactive when injected IP. Increasing doses of dermorphin IP (from 12 to 6400 μg/kg) inhibit intestinal propulsion to the same extent irrespectively of the doses employed, but never by more than 50%. Only a high dose of naloxone (30 mg/kg/IP) antagonizes this IP effect. The central and peripheral components of this intestinal effect of dermorphin are discussed. |
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Keywords: | Intestinal motility Dermorphin Morphine Naloxone Quaternary naloxone |
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