Effects of Food Deprivation and Methamphetamine on Fixed-Ratio Schedules of Intracranial Self-Stimulation

Abstract

Six rats were implanted with electrodes in the posterior medial forebrain area and trained to bar press for crf ICSS and then shifted to FR schedule of reinforcement. It was observed that Ss had to be “primed” on crf at the beginning of each session; FRs greater than 20 to 30 were not typical, but depriving S of food for 48 hr. increased the size of the terminal ratio; with injection of .3 mgm. methamphetamine, S would hold FR-110; and the contributing influence of long exposure co FR, food starvation, and methamphetamine are consistently reversible. It was concluded that the properties of FR ICSS controlled responding are in many respects unlike the behavioral characteristics of the same response class modified and sustained by FR application of more conventional rewards.