Food- and drug-reinforced responding: effects of DITA and d-amphetamine.

Intravenous pretreatment with DITA (0.1 - 1.0 mg/kg) decreased the rate of food-reinforcement lever pressing in rhesus monkeys. Response rate decreases were dose-dependent but showed the development of tolerance. Self-administration of DITA was initiated and maintained in each of three monkeys when 30 lever presses were required to produce each injection. Maximal response rate during periods of drug availability was maintained by 0.03 mg/kh/injection while higher and lower doses (0.01 and 0.10 mg/kg/injection) maintained lower response rates. Response rate in periods of food availability immediately preceding drug periods was relatively constant across session; response rate in periods of food availability immediately following drug periods, however, decreased with increasing amounts of drug self-administered. Replication of initial self-administration doses produced results comparable to original determinations in contrast to the tolerance observed with DITA effects upon food-reinforced responding. DITA was about 3 times less potent than d-amphetamine in maintaining response rates in drug periods and in decreasing the rate of subsequent food-reinforced responding.