title: Antinociceptive effects of combining low doses of neuroleptic drugs and fentanyl in sheep.
abstract: Effects of low doses of the neuroleptic drugs droperidol and zuclopenthixol, combined with a subanalgesic dose of the opioid mu-agonist, fentanyl, on mechanical nociceptive thresholds were evaluated in sheep. Intravenously administered droperidol (5 micrograms/kg of body weight) did not induce any change in the nociceptive thresholds when administered alone, but caused marked increase in threshold responses when combined with a subanalgesic dose of fentanyl (5 micrograms/kg). Similarly, a combination of i.v. administered zuclopenthixol (100 micrograms/kg) and fentanyl induced significant (P < 0.05) antinociceptive effects, whereas zuclopenthixol administered i.v. alone had no effect on the threshold responses. Intrathecal administration of a low dose of droperidol (5-micrograms total dose) combined with i.v. administered fentanyl also increased mechanical thresholds significantly (P < 0.05). These results indicate that interactions exist between dopaminergic and opioid systems in the processing of nociceptive information and that these effects may, at least partially, be mediated spinally.
authors.affiliation: Department of Veterinary Surgery, University of Bristol, England.
authors.forename: A E
authors.initials: AE
authors.lastname: Kyles
authors.forename: A E
authors.initials: AE
authors.lastname: Waterman
authors.forename: A
authors.initials: A
authors.lastname: Livingston
authors.forename: B
authors.initials: B
authors.lastname: Vetmed
mesh_terms: D000818:Animals; D003006:Clopenthixol / Q000008:administration & dosage / Q000494:pharmacology; D004329:Droperidol / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D005283:Fentanyl / Q000008:administration & dosage / Q000494:pharmacology*; D007275:Injections, Intravenous / Q000662:veterinary; D007278:Injections, Spinal / Q000662:veterinary; D009619:Nociceptors / Q000187:drug effects* / Q000502:physiology; D017288:Pain Threshold / Q000187:drug effects; D012756:Sheep / Q000502:physiology*
chemical_list: D003006:Clopenthixol; D004329:Droperidol; D005283:Fentanyl