Some drug effects influencing barbiturate facilitation of water ingestion

Abstract

Pentobarbital was studied in combination with chlorpromazine and a stimulant barbiturate (5 ethyl, 5, 1, 3, dimethyl-2-butenyl barbituric acid) with respect to water intake in the rat. Each depressed water intake when administered alone. Pentobarbital increased drinking in the dosage employed. Chlorpromazine blocked totally the usual pentobarbital facilitation so that the combined effect was the same as that for chlorpromazine alone. The stimulant barbiturate antagonized the pentobarbital effect so that a constant difference between the stimulant and its control was obtained. The effect of the sodium salts of barbital, pentobarbital and phenobarbital upon water intake in the 23 1/2-hour water-deprived rat was also studied. A significant parabolic relationship was found between water intake and dosage, with water intake rising at low dosages and falling at higher dosages. The dosage of the drugs investigated yielding maximum facilitation of water intake varied with the hypnotic dosage. Finally, the extent of facilitation of water intake was found to vary for the different drugs. Two major conclusions are drawn: first, there is a hypnotic dimension of action affecting water intake within the barbiturate family; second, there is another dimension of action which relates to the extent of facilitation.