title: Is there any cross-antagonism between mu-opioid and alpha 2-adrenergic receptors in the rat spinal cord?
abstract: A functional connection, evidenced by synergism and cross-tolerance, seems to exist between the mu-opioid and the alpha 2-adrenergic receptors in the superficial dorsal horn of the rat spinal cord. In this study possible cross-antagonism between these systems was studied by intrathecal administration of morphine 2.5 micrograms or dexmedetomidine 1.25 micrograms 15 min. after subcutaneous injection of naloxone 1.0 mg/kg or atipamezole 3.0 mg/kg in the morphine group and 4.0 mg/kg or 1.0 mg/kg in the dexmedetomidine group, respectively. No cross-antagonism of the antinociceptive effect was seen either in the tail flick or in the hot plate test at 15, 30, 45 and 60 min. from the pretreatment.
mesh_terms: D058669:Adrenergic alpha-2 Receptor Antagonists; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D004347:Drug Interactions; D007093:Imidazoles / Q000494:pharmacology; D008297:Male; D020926:Medetomidine; D009020:Morphine / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017450:Receptors, Opioid, mu / Q000037:antagonists & inhibitors*; D013116:Spinal Cord / Q000187:drug effects* / Q000378:metabolism
chemical_list: D058669:Adrenergic alpha-2 Receptor Antagonists; D000317:Adrenergic alpha-Antagonists; D000701:Analgesics, Opioid; D007093:Imidazoles; D009292:Narcotic Antagonists; D017450:Receptors, Opioid, mu; C050701:atipamezole; D009270:Naloxone; D009020:Morphine; D020926:Medetomidine