Persistence of drug experience in rats formerly dependent on phenobarbital or meprobamate

The rats of groups I, II, III and IV were treated orally with phenobarbital, meprobamate, codeine and vehicle, respectively, for total 21 days, and then drugs were withdrawn. All these rats were given again orally phenobarbital for 5 days starting from 70 days after the withdrawal. In comparison with groups III and IV, groups I and II showed larger weight gain during phenobarbital re-administration and longer-lasting weight loss and an larger increase in body temperature after the termination. These results suggested that the drug experience on sedative-hypnotics persisted over two months after the withdrawal and that did not cross to that of narcotics.