Effects of d -amphetamine, scopolamine, chlordiazepoxide and diphenylhydantoin on self-stimulation behavior and brain acetylcholine

Abstract

The effects of d-amphetamine (0.25–8), scopolamine (0.25–8), chlordiazepoxide (2.5–40), and diphenylhydantoin (25–75), given i.p. or s.c. on a mg/kg basis, were studied on self-stimulation behavior in the male albino rat. The dose-effect relationships, the role of baseline rates of responding and their effects on brain acetylcholine (ACh) were determined in rats trained to self-stimulate for electrical reward in the lateral posterior hypothalamus. The effects of d -amphetamine were both dose and baseline-rate dependent. Low-moderate doses (0.5–2.0 mg/kg inclusive) facilitated self-stimulation and larger doses (2.0 to 8.0 mg/kg) depressed responding. Baseline rates before d -amphetamine administration were extremely important in the effect observed. Low rates of responding were facilitated and high rates were depressed by this agent. The effects of scopolamine in a wide range of dosage were less consistent. A small dose (0.5 mg/kg) facilitated only transiently self-stimulation and larger doses (1–8 mg/kg) tended to depress this behavior. Baseline rate effects were less important but high-rate responders were usually depressed by scopolamine.