Amphetamine-Induced Locomotion and Brain Stimulation Reward Research and Applications

Amphetamine, a dopamine agonist, has an effect on increasing dopamine level in certain brain regions, like the nucleus accumben and the ventral tegmental area (Yoshida et al., 1992). Hence, it increases reward-related functions. In the current study, we examined the changes in the frequency of locomotion in previously habituated mice after 3mg/kg amphetamine injections. In the same way, we also monitored the changes in bar pressing rates of previously trained rates after 2mg/kg amphetamine injections. Though not showing a significant statistical result, both graphs and discussions supported that amphetamine injection increased horizontal quadrants crossings compared with saline injection. While the amphetamine administration increased bar press rate in previously trained rats at low frequencies, it led the rats to fewer bar presses at higher frequencies compared with both the baseline and the saline condition. The results of both experiments consistent with past studies which claim that amphetamine acts as a dopaminergic agonist and increases reinforcing capacity through enhancement of dopaminergic transmission (Gallistel & Karras, 1984).

Differential Activity in Rats as a Function of Deprivation, Stimulus Change, and Recording Method

The effects of stimulus changes on activity in 20 food-deprived and 20 nondeprived adult rats were studied using a photo-relay method, direct observation, and bar-press rate. Differences in activity as measured by the photo-cells and differences in bar-presses were significant ( p < .001) for stimulation, deprivation, and the interactions. Ss in the stimulus change groups had the highest activity counts, their most frequent single behavior being exploration. The results confirmed the utility of the photo-relay system of measurement, demonstrated that stimulus change differentially affected the activity of deprived and nondeprived Ss, and supported the conclusion that stimulation sensitized S to its internal state to which it then reacted.