Ethanol exhibits alpha receptor blocking-like properties in anesthetized rats.
The ability of ethanol to reduce alpha-adrenergic receptor-mediated pressor responsiveness in vivo was investigated in chloralose-anesthetized male Sprague-Dawley rats. Catheters were inserted in the jugular vein and the femoral artery of rats for the injection of drugs and the measurement of blood pressure, respectively. Dose-response curves for phenylephrine and norepinephrine were constructed by plotting the change in mean arterial pressure following a bolus dose of the agent against the dose of the pressor agent used. Following construction of an initial dose-response curve, animals were challenged with either a 1 g/kg dose of ethanol or an equivalent volume of saline (iv) and the dose-response curves were repeated. Using a similar protocol, pressor responsiveness was evaluated in animals pretreated with either yohimbine (1 mg/kg) or prazosin (3.9 micrograms/kg), a dose sufficient to produce partial blockade of alpha receptor-mediated pressor responsiveness, and then treated with ethanol. Ethanol produced a partial blockade of alpha receptors when the animals were challenged with either phenylephrine or norepinephrine. This blockade produced by ethanol was shown to be similar to that produced by the receptor blocking agents used in this study. To rule out any nonspecific effects of ethanol in reducing vascular reactivity, some animals were challenged with angiotensin II both before and after treatment with ethanol, yohimbine, or prazosin and after both drugs were administered together. Ethanol, as well as the alpha 1- and alpha 2-adrenergic blocking agents tested failed to have any significant effect on angiotensin II-pressor responsiveness, ruling out any nonspecific effect of ethanol on the vasculature. It is concluded, therefore, that ethanol has alpha receptor blocking-like activity in vivo.
Russ
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RD
Department of Pharmacology, School of Medicine, East Carolina University, Greenville, North Carolina 27858.
Abdel-Rahman
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AA
Wooles
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WR
D000768:Anesthesia, General; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D000431:Ethanol / Q000494:pharmacology*; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D012016:Reference Values; D015016:Yohimbine / Q000494:pharmacology
D011942:Receptors, Adrenergic, alpha; D010656:Phenylephrine; D015016:Yohimbine; D000431:Ethanol; D009638:Norepinephrine; D011224:Prazosin