General Pharmacology: The Vascular System
General papersEthanol abolishes clonidine-induced impairment of baroreflex control of heart rate in conscious rats
Section snippets
Preparation of the rats
Male Wistar rats (300–360 g; High Institute of Public Health, Alexandria, Egypt) were used in the present study. For measurement of blood pressure, the method described in previous studies El-Mas and Abdel-Rahman 1992, El-Mas and Abdel-Rahman 1993a was adopted. Briefly, the rats were anesthetized with thiopental (50 mg/kg, IP). Catheters (polyethylene 50) were placed in the abdominal aorta and vena cava through the femoral artery and vein for measurement of blood pressure and IV administration
Acute and short-term effects of ABD on baseline MAP and HR
Section of the aortic depressor nerves while the rats were anesthetized with thiopental resulted in immediate and statistically significant (p < 0.05) increases in MAP (from 111 ± 4 to 138 ± 5 mmHg) and HR (from 391 ± 10 to 423 ± 9 beats/min). In SO rats, no significant change in either variable was demonstrated (data not shown). Administration of a test dose of phenylephrine (8 μg/kg) before and after aortic baroreceptor denervation or sham operation revealed that the pressor effect of
Discussion
The most important finding of the present study was that prior administration of ethanol (1 g/kg) abolished the depressant effect of subsequently administered clonidine on BRS in conscious ABD rats. That this effect of ethanol was not associated with any alteration in the hypotensive effect of clonidine may add further support to the dissociation between the hypotensive effect of clonidine and its interaction with baroreflex function. These findings may suggest a modulatory role for ethanol on
Acknowledgements
Supported by the Faculty of Pharmacy, University of Alexandria, Egypt.
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