Chronic ethanol attenuates centrally-mediated hypotension elicited via alpha(2)-adrenergic, but not I(1)-imidazoline, receptor activation in female rats.
OBJECTIVE
This study dealt with the effect of chronic ethanol administration on hemodynamic responses elicited by alpha(2)-adrenergic (alpha-methyldopa) or I(1)-imidazoline (rilmenidine) receptor activation in telemetered female rats.


METHODS
The effects of alpha-methyldopa or rilmenidine on blood pressure (BP), heart rate (HR) and their variability were investigated in rats that received liquid diet without or with ethanol (5% w/v) for 12 weeks. To evaluate the effect of each drug on cardiovascular autonomic control (BP and HR variability) in the absence or presence of ethanol, three time-domain indices of hemodynamic variability were measured: (i) standard deviation of mean arterial pressure (SDMAP), (ii) standard deviation of beat-to-beat intervals, and (iii) root mean square of successive differences in R-R intervals.


RESULTS
In liquid diet-fed control rats, i.p. rilmenidine (600 microg/kg) or alpha-methyldopa (100 mg/kg) reduced BP along with decreases and increases, respectively, in HR. Both drugs had no effect on HR variability but reduced BP variability (SDMAP), suggesting a reduced vasomotor sympathetic tone. Ethanol feeding attenuated reductions in BP and SDMAP evoked by alpha-methyldopa but not by rilmenidine.


CONCLUSIONS
We conclude that chronic ethanol preferentially compromises alpha(2)- but not I(1)-receptor-mediated hypotension in female rats probably via modulation of vasomotor sympathetic activity. These findings highlight the adequacy of rilmenidine use to lower BP in hypertensive alcoholic females.
El-Mas
Mahmoud M
MM
Department of Pharmacology, School of Medicine, East Carolina University, Greenville, NC 27834, USA.
Abdel-Rahman
Abdel A
AA
D000818:Animals; D019540:Area Under Curve; D001794:Blood Pressure / Q000187:drug effects*; D000431:Ethanol / Q000494:pharmacology*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D054755:Imidazoline Receptors / Q000502:physiology*; D008750:Methyldopa / Q000494:pharmacology; D010080:Oxazoles / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018341:Receptors, Adrenergic, alpha-2 / Q000502:physiology*; D000077769:Rilmenidine
D054755:Imidazoline Receptors; D010080:Oxazoles; D018341:Receptors, Adrenergic, alpha-2; C410887:imidazoline I1 receptors; D000431:Ethanol; D008750:Methyldopa; D000077769:Rilmenidine