Some behavioral effects of repeated d-amphetamine administrations. Drug Dev. Res. 20:31-41, 1990.
Effects of daily administrations of d-amphetamine were studied on key peck responses of pigeons maintained under a multiple fixed-interval2-min, fixed-ratio 30-response schedule. Under the fixed-interval schedule, a pause was followed by a transition to increasing rates of responding until food presentation. Under the fixed-ratio schedule, higher sustained rates of responding were maintained. Low to intermediate doses (0.3-1 .O mg/kg) of d-amphetamine changed the temporal patterns and occasionally increased rates of responding under the fixed-interval schedule. Higher doses decreased rates of responding under both schedules. With daily injections of 1 .O mgikg d-amphetamine prior to experimental sessions, the effects of this dose on rates and patterns of responding were attenuated, and d-amphetamine dose-effect curves were shifted to the right, primarily under the fixed-ratio schedule. Similar results were obtained with daily presession injections of 5.6 mg/kg d-amphetamine in a second group of pigeons, except that rates of responding under both schedules were decreased by this daily dose, and did not return completely to control values with repeated injections. In a third group of pigeons, 1 .O mgikg d-amphetamine administered daily, after experimental sessions, did not alter dose-effect functions for d-amphetarnine. In a second experiment, pigeons were trained to peck one response key when given 1.0 mgikg damphetamine and a different key when given presession water injections. Increasing doses