Serotonin blockade in conscious, unrestrained cirrhotic dogs with portal hypertension†

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Abstract
It has recently been reported that the administration of ketanserin, a serotonin antagonist, was associated with a significant reduction in portal pressure both in portal hypertensive rats and cirrhotic patients. However, this beneficial effect on splanchnic hemodynamics was accompanied by a significant reduction in arterial pressure. Using conscious dogs, we investigated the effect of the chronic oral administration of a new specific antiserotonergic drug, ritanserin (10 mg per day for 5 days), on portal pressure and systemic hemodynamics. Eleven dogs with secondary biliary cirrhosis and portal hypertension due to chronic bile duct ligation were evaluated. One week prior to study, heparinized catheters were placed in the portal vein and brought subcutaneously to the dorsal cervical area. Measurements were made under baseline conditions, following ritanserin administration and 72 hr after the last dose. Ritanserin administration caused a significant reduction in portal pressure (from 17.3 ± 3.1 mmHg to 13.6 ± 4.5 mmHg; mean decrease: 23.1%; p<0.001). Maximal effects on portal pressure were reached on the fourth day. During the recovery period, hemodynamic parameters returned to baseline values. In six of the 11 cirrhotic dogs with successful chronic catheterization of the inferior vena cava and aorta, ritanserin administration did not cause significant changes in the mean arterial pressure, heart rate, cardiac output and peripheral vascular resistance. These data indicate that chronic implantation of venous and arterial catheters in dogs with secondary biliary cirrhosis is a useful experimental model for pharmacological studies of portal hypertension in conscious animals. The selective effect of ritanserin on portal pressure of portal hypertensive dogs indicates that this drug may be of value in the medical treatment of portal hypertension.

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