[Role of alpha 1 adrenergic receptors in water balance in the rat].

The effects of phenylephrine (alpha 1 +) and prazosin (alpha 1 -) on water intake, diuresis, food intake and blood pressure were compared in conscious normal and diabetic insipidus (DI) Long Evans rats. The two drugs did not change the values measured on 24 hours in the two groups of animals (tables I and II). Phenylephrine induced a diuretic response in both normal and DI rats during the two first hours. Water intake was decreased in normal rats and increased in DI animals (fig. 1). Prazosin induced an antidiuretic effect in the two groups of animals, an increase in water intake in normal rats and a decrease in water intake in DI animals (fig. 2). Blood pressure was not changed in the two groups of animals two hours after injection. The comparison between the different results shows that the first changes induced by phenylephrine or prazosin were changes in diuresis. Since the two drugs act in a same way on the diuresis of normal and vasopressin--deprived rats, it is concluded that the neurohypophysial peptide is not involved in the variations of urinary volume induced by the alpha 1-adrenergic drugs.