Dose and time as variables in barbiturate action upon water ingestion

¹ Department of Psychiatry and Neurology, Washington University School of Medicine, St. Louis, Missouri

The effect of phenobarbital, amobarbital, and secobarbital upon the volume of water ingested by thirsty rats was investigated shortly after injection, 1 day later, and 2 days later. The first effect was the characteristic rise in water intake at low dosages, and a fall at higher dosages. Twenty-four hours later there is a fall at the lower dosages, and a rise at the higher quantities. Two days after injection, there was some quite slight residual effect of both amobarbital and secobarbital but equilibration was nearly complete. Phenobarbital demonstrates some depressant activity at this time. When phenobarbital is administered and water ingestion held at a constant level for 2 days, the depressant effect is still obtained. These data indicate that the barbiturates have sequential effects upon water ingestion which are to some large degree independent of water balance per se.