Hippocampal injections of magnesium pemoline and the extinction of a bar press response in rats

Stainless steel cannulae were implanted in the medial hippocampus of 24 rats. The subjects were then trained to press a bar for milk reinforcement. After a fixed amount of training the animals were divided into four groups. A control group received injections of Holman's ringer (via the cannulae) while each of three experimental groups received a different dose of magnesium pemoline. The animals then performed an additional number of bar presses. Twenty-four hours later the time and number of bar presses to an extinction criterion were measured. The low and medium drug-dose group exhibited increased resistance to extinction. The results were discussed with regard to the effect magnesium pemoline has on performance variables and RNA synthesis.This work was supported by Australian Research Grants Committee and Sigma Xi funds to Dr. J. C. Saunders. The authors gratefully acknowledge the assistance of Mr. G. R. Bock and Mrs. J. Sack and thank Abbott Laboratories for supplying the drug.