Bromocriptine-induced hypothermia in Balb/C mice: its possible mechanism of action.
1. Administration of bromocriptine (0.1-2.5 mg/kg, i.p.) to mice produced hypothermia. 2. Pretreatment with the alpha 1-adrenoceptor blocker, prazosin (2.0 mg/kg, i.p.) or the alpha 2-adrenoceptor antagonist yohimbine (2.5 mg/kg, i.p.) had no effect on this response. 3. The inhibitor of catecholamine synthesis, alpha-methyl-p-tyrosine, and the muscarinic antagonist, atropine (10 mg/kg, i.p.) failed to alter the hypothermia. 4. Pretreatment with the dopamine (DA) receptor antagonists haloperidol (0.02 mg/kg, i.p.) or cis-flupenthixol (0.01 mg/kg, i.p.) completely blocked this response while trans-flupenthixol (0.05 mg/kg, i.p.) was inactive. 5. Depletion of 5-HT in the brain by p-chlorophenylalanine reduced the hypothermic response. 6. Similarly, pretreatment with the serotonergic (5-HT) receptor blocker ketanserin (1 mg/kg, i.p.) attenuated the hypothermia and at a dose of 2 mg/kg (i.p.) it completely blocked the hypothermic response. 7. Methysergide (5 mg/kg, i.p.) was also effective in antagonizing the hypothermia. 8. It was concluded that both DA and 5-HT mechanisms are involved in bromocriptine-induced hypothermia in mice.
Mustafa
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Department of Medical Pharmacology, College of Medicine, King Saud University, Saudi Arabia.
D000109:Acetylcholine / Q000502:physiology; D000818:Animals; D001831:Body Temperature / Q000187:drug effects*; D001971:Bromocriptine / Q000494:pharmacology*; D004298:Dopamine / Q000502:physiology; D018492:Dopamine Antagonists; D005260:Female; D051379:Mice; D008807:Mice, Inbred BALB C; D009638:Norepinephrine / Q000502:physiology; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects; D012701:Serotonin / Q000502:physiology; D012702:Serotonin Antagonists / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects
D018492:Dopamine Antagonists; D011942:Receptors, Adrenergic, alpha; D012702:Serotonin Antagonists; D012701:Serotonin; D001971:Bromocriptine; D000109:Acetylcholine; D004298:Dopamine; D009638:Norepinephrine