Dopamine receptor mediated hypothermic action of B-HT 920 in rats.

Abstract

The hypothermic action of the thiazoloazepine derivative B-HT 920, an alpha 2-adrenoceptor agonist has been investigated in rats. B-HT 920 (6-allyl-2-amino-5,6,7,8-tetrahydro-4H-thiazolo-(4,5-d)-azepine dihydrochloride) (0.25-1.0 mg kg-1 i.p.) induced a dose-dependent hypothermia. This peak effect was seen within 60-90 min and lasted up to 120 min. Its action was potentiated by the selective D1-dopamine agonist SKF 38393 and inhibited by the D2-antagonists haloperidol (1 mg kg-1) and sulpiride (100 mg kg-1). The hypothermic action of B-HT 920 was centrally mediated; i.c.v. administration of 10 micrograms produced a significant fall in rectal temperature which was sensitive to blockade by haloperidol. B-HT 920 also potentiated the hypothermic action of apomorphine (0.1 and 0.5 mg kg-1) in a haloperidol sensitive manner. Reserpine (5 mg kg-1 i.p.) pretreatment reduced the hypothermic response of B-HT 920 (0.5 mg kg-1) but sensitized the response due to the combination of B-HT 920 (0.5 mg kg-1) and apomorphine (0.1 mg kg-1). Neither the selective alpha 2-adrenoceptor antagonists, yohimbine (1 mg kg-1) or idazoxan (1 mg kg-1), the histamine antagonist mepyramine (10 mg kg-1) nor the 5-HT antagonist cyproheptadine (5 mg kg-1) inhibited B-HT 920-induced hypothermia. Similarly, the selective alpha 1-antagonist prazosin (1 mg kg-1) and the beta-antagonist propranolol (10 mg kg-1) failed to modify the hypothermic action of B-HT 920. These observations demonstrated hypothermia induced by B-HT 920 is mediated by postsynaptic D2-receptors and D1- and D2-receptor interplay is essential for the full expression of hypothermia in rats.

• Authors: A Verma, S K Kulkarni
• Journal: The Journal of pharmacy and pharmacology (J Pharm Pharmacol) Vol. 43 Issue 6 Pg. 421-4 (Jun 1991) ISSN: 0022-3573 [Print] England
• PMID: 1681056 (Publication Type: Journal Article)

Chemical References

• Adrenergic alpha-Antagonists
• Azepines
• Dopamine Agents
• Receptors, Dopamine
• Receptors, Dopamine D2
• 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine
• talipexole
• Reserpine
• Haloperidol
• Apomorphine

Topics

• 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine (pharmacology)
• Adrenergic alpha-Antagonists (pharmacology)
• Animals
• Apomorphine (pharmacology)
• Azepines (pharmacology)
• Body Temperature (drug effects)
• Dopamine Agents (pharmacology)
• Dose-Response Relationship, Drug
• Female
• Haloperidol (pharmacology)
• Injections, Intraventricular
• Male
• Rats
• Rats, Inbred Strains
• Receptors, Dopamine (drug effects)
• Receptors, Dopamine D2
• Reserpine (pharmacology)