Appetitive control of responding in the presence of free food: Effects of d-amphetamine and fenfluramine

Abstract

d-Amphetamine (1-4 mg/kg) significantly decreased responding for food in the presence of free food. This effect is opposite to that obtained in experiments on motor activity and responding for stimulus change but is in agreement with predictions based on its anorectic activity. Fenfluramine (2-8 mg/kg), an anorectic with qualitatively different effects on motor activity at anorectic doses, similarly decreased responding for food in the presence of free food. These results suggest that the appetitive properties of response contingent food play a major role in the maintenance of responding in the presence of free food, even if only as part of a stimulus complex whose significance was established during early training.

Enhanced penetration of neutral-beam-injected ions by vertically asymmetric toroidal-field ripple

“…In the presence of a magnetic well, an ion may spend larger or smaller amounts of time at the tips of its banana, depending on its phase with respect to the ripple; this lingering period determines the extent of its radial drift at the banana tips. With symmetric ripple this process gives rise to a stochastic wandering of banana orbits, even in the absence of collisions [11]. In the presence of vertically asymmetric ripple, the stochastic motion is replaced by a steady outward drift [12], since banana orbits consistently bounce early in the region of larger ripple.…”