The effect of clonidine injected centrally on serum-free fatty acids and glucose concentration in the rat.
Clonidine administered intracerebroventricularly (ICV) to conscious rats induced a significant dose-dependent increase in serum free fatty acid (FFA) and blood glucose levels. The rise in FFA and glucose concentrations after a dose of 10 micrograms averaged 80%-100% of the control levels. The alpha-adrenoceptor antagonists yohimbine, phentolamine, and phenoxybenzamine, administered alone ICV, did not substantially influence the control FFA and glucose levels. A hyperlipemic response to clonidine (10 micrograms) was abolished by an ICV pretreatment with yohimbine and was strongly antagonized by phentolamine but not by phenoxybenzamine. The clonidine-induced hyperglycemia was significantly diminished by phentolamine and only partly by yohimbine, whereas phenoxybenzamine was ineffective here. The histamine H2-receptor antagonist cimetidine, given ICV, failed to change these effects of clonidine. It seems likely that clonidine, given ICV, induces hyperlipemic and hyperglycemic effects through the stimulation of central alpha-adrenoceptors but not histamine H2-receptors. The lipolytic action of the drug depends more on the activation of alpha 2-adrenoceptors.
D000818:Animals; D001786:Blood Glucose / Q000032:analysis*; D003000:Clonidine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005230:Fatty Acids, Nonesterified / Q000097:blood*; D007276:Injections, Intraventricular; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains
D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D003000:Clonidine