Behavioral alterations during prolonged low level continuous amphetamine administration in a monkey family group (Cercopithecus aethiops).

The continuous presence of endogenous psychotomimetic compounds has frequently been hypothesized in human psychopathology. In related drug-based animal models it would be necessary to demonstrate accumulating behavioral abnormalities despite a low constant drug-level. Using subcutaneously implanted slow-release capsules containing a d-amphetamine base, we studied behavioral effects during 11-weeks of low level but continuous release of this psychotomimetic drug in a socially housed family group of monkeys (drugged father and mother with undrugged infant). Following implantation, locomotion was only slightly affected throughout the drug period. Among visual behaviors, staring gradually increased and, after 5-7 weeks, peaked at a level ten-fold higher than pre-implant levels. Except for infant/female contact, social behaviors were decreased throughout the drug period. Sleep during nights declined by about one-third for the first 8 weeks. In vitro measurements of this capsule type confirmed amphetamine release at 1st-week levels for ca. 8 weeks. Low level prolonged amphetamine intoxication apparently can lead to increasing behavioral abnormalities despite relatively stable drug-release levels.