Alpha 2-adrenoceptor- and D2-dopamine receptor-mediated analgesic response of B-HT 920.
The involvement of D2-dopamine receptors in the antinociceptive action of B-HT 920 (2-amino-6-allyl-5,6,7,8-tetrahydro-(4H) thiazolo-(4,5d)-azepine) has been investigated in mice. B-HT 920 (0.1-2.0 mg kg-1) and apomorphine (0.1-2.0 mg kg-1) produced a dose-dependent increase in tail flick latency. Analgesia induced by apomorphine was blocked by the D2-antagonist, haloperidol (1 mg kg-1) but not by the opioid antagonist, naloxone (1 mg kg-1). The antinociceptive action of B-HT 920 was potentiated by the D1-agonist SKF 38393 (5 mg kg-1), an action antagonized by haloperidol. The selective alpha 2-adrenoceptor blocking drug yohimbine (1 mg kg-1) and naloxone (1 mg kg-1) blocked the antinociceptive action of B-HT 920 (1 mg kg-1). Haloperidol, however, failed to modify the B-HT 920-induced increase in tail flick latency. B-HT 920 and apomorphine reversed reserpine (2 mg kg-1) 4 h-induced hyperalgesia. The reversing action of apomorphine was blocked by haloperidol but not by yohimbine. Thus, a role of alpha 2-adrenoceptors and D2-dopamine receptors is postulated in the antinociceptive action of B-HT 920.
Verma
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Department of Pharmaceutical Sciences, Panjab University, Chandigarh, India.
Kulkarni
S K
SK
D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine / Q000494:pharmacology; D000698:Analgesia; D000818:Animals; D001058:Apomorphine / Q000037:antagonists & inhibitors; D001381:Azepines / Q000494:pharmacology*; D015259:Dopamine Agents / Q000494:pharmacology*; D005260:Female; D006220:Haloperidol / Q000494:pharmacology; D008297:Male; D051379:Mice; D009270:Naloxone / Q000494:pharmacology; D010147:Pain Measurement; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D011954:Receptors, Dopamine / Q000187:drug effects*; D017448:Receptors, Dopamine D2
D001381:Azepines; D015259:Dopamine Agents; D011942:Receptors, Adrenergic, alpha; D011954:Receptors, Dopamine; D017448:Receptors, Dopamine D2; D009270:Naloxone; D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; C024763:talipexole; D006220:Haloperidol; D001058:Apomorphine