title: Interaction between halothane and mu, delta and kappa opioid agonists on the isolated right atria of the rat.
abstract: We have examined the interaction between halothane and specific opioid agonists at mu (morphine and [D-ala2 N-mephe4, gly-ol5]-enkephalin (DAGO)), delta ([D-pen2,5]-enkephalin (DPDPE)) and kappa (trans-3,4-dichloro-N-methyl-N-[2-(1-pyrroliknyl)cyclohexyl]- bencetamide methane sulphonate (U-50,488H)) receptors on the isolated right atria of the rat. All the opioid agonists tested decreased atrial rate. The maximal effects obtained with U-50,488H (75 (SE 3.3)%) were significantly (P < 0.001) greater than those obtained with morphine (12 (2.7)%), DAGO (8 (0.6)%) or DPDPE (11 (1.8)%). Halothane 1.5 v/v% did not modify the inhibitory effects induced by morphine, DAGO or DPDPE. However, U-50,488H had a potentiating effect in the presence of halothane 1.5 v/v% (P < 0.001). Naloxone 5 x 10(-7) and 1 x 10(-6) mol litre-1 antagonized the inhibitory effects of U-50,488H in the presence of halothane. We conclude that halothane increased the potency of a kappa agonist on isolated right atria and suggest that this effect was mediated by opioid receptors.
authors.affiliation: Department of Anesthesiology, Virgen de la Arrixaca Hospital, Murcia, Spain.
authors.forename: J A
authors.initials: JA
authors.lastname: Micol
authors.forename: M L
authors.initials: ML
authors.lastname: Laorden
mesh_terms: D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D000700:Analgesics / Q000494:pharmacology; D000818:Animals; D016275:Atrial Function / Q000187:drug effects*; D046508:Culture Techniques; D004347:Drug Interactions; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D020881:Enkephalin, D-Penicillamine (2,5)-; D004745:Enkephalins / Q000494:pharmacology; D005260:Female; D006221:Halothane / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects*; D008297:Male; D009020:Morphine / Q000494:pharmacology; D011759:Pyrrolidines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011957:Receptors, Opioid / Q000502:physiology*
chemical_list: D000700:Analgesics; D004745:Enkephalins; D011759:Pyrrolidines; D011957:Receptors, Opioid; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D009020:Morphine; D020881:Enkephalin, D-Penicillamine (2,5)-; D006221:Halothane