Sexually dimorphic hemodynamic effects of intragastric ethanol in conscious rats

This study investigated the gender-related differences in hemodynamic effects of small to moderate doses of intragastrically (i.g.) administered ethanol in conscious rats. Changes evoked by ethanol (0.25, 0.5 or 1 g/kg) in mean arterial pressure (MAP), heart rate, cardiac index (CT), stroke volume (SV), and total peripheral resistance (TPR) were followed for 90 min in age-matched male and female Sprague-Dawley rats. Baseline values of MAP (121+/-2 vs 124+/-2 mmHg) were similar whereas CI (55+/-2 vs 43+/-2 ml/min/100 g) and TPR (2.2+/-0.1 vs 3.0+/-0.1 mmHg/ml/min/100 g) were significantly (P<0.05) higher and lower, respectively, in female compared with male rats. In male rats, the middle dose (0.5 g/kg) of ethanol caused a slight increase in MAP due to significant (P<0.05) increases in CO whereas the other two doses (0.25 and 1 g/kg) had no effect on MAP. In female rats, MAP was not affected by ethanol (0.25 and 0.5 g/kg) and showed a significant reduction by the higher dose (1 g/kg) that was associated with decreases in CO and SV while TPR did not change. The hypotensive effect of ethanol (1 g/kg) in female rats started after 50 min, was maximal (13+/-1.7 mmHg) at 70 min and remained so for the remaining 20 min of the study. Blood ethanol concentrations were similar in male and female rats. These findings suggest that the hemodynamic responses to i.g. ethanol are gender-related and that ethanol-evoked hypotension in female rats appears to involve a reduction in cardiac output.