title: D2 dopamine receptor involvement in spinal dopamine-produced antinociception.
abstract: Experiments were performed on 79 lightly pentobarbital-anesthetized rats. Rats displayed a dose-dependent increase in tail-flick latencies following the injection of dopamine (DA) into the lumbar subarachnoid space through an intrathecal tube. Sulpiride, a D2-subtype receptor antagonist, antagonized the DA-induced analgesia (antinociceptive) effect; while SCH-23390, a D1-subtype receptor antagonist, had no effect even in a higher dose. To further investigate whether the well-known spinal serotonergic, noradrenergic and opioidergic receptor systems were involved in DA-induced antinociception, their antagonists, methysergide, phentolamine, and naloxone were tested respectively. The results showed that phentolamine, but not methysergide or naloxone, could block the DA-induced antinociception. The present data provide evidence that DA exerts antinociceptive effects through D2-subtype dopamine receptor(s) at the spinal level, and that spinal alpha-adrenergic receptors may mediate this effect.
authors.affiliation: Department of Neurobiology, Shanxi Medical College, Taiyuan, P.R. China.
authors.forename: Q S
authors.initials: QS
authors.lastname: Liu
authors.forename: J T
authors.initials: JT
authors.lastname: Qiao
authors.forename: N
authors.initials: N
authors.lastname: Dafny
mesh_terms: D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D004298:Dopamine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D008297:Male; D008784:Methysergide / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology; D009619:Nociceptors / Q000187:drug effects* / Q000502:physiology; D010646:Phentolamine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017448:Receptors, Dopamine D2 / Q000187:drug effects* / Q000502:physiology; D013116:Spinal Cord / Q000187:drug effects* / Q000502:physiology; D013469:Sulpiride / Q000494:pharmacology; D013997:Time Factors
chemical_list: D001552:Benzazepines; D017448:Receptors, Dopamine D2; D009270:Naloxone; D013469:Sulpiride; D004298:Dopamine; D008784:Methysergide; D010646:Phentolamine