Effect of Adenine and Caffeine Injections on Behavior of Rats in a Circular Maze

Abstract

Albino rats were trained in a large circular maze until they were able to run from the periphery to the center in the shortest time possible and without making an error. Such trained animals were then given different doses of caffeine and adenine separately and also in combination; the running time, the number of errors, and the general behavior of the rats were noted at various intervals thereafter. Thirty young adult rats, weighing from 100 to 200 gm., were used in these experiments. The dosages varied from 1 to 5 mg. per hundred gm. weight of the animals; the drugs were administered by intraperitoneal injection. In other experiments, the different drugs were given to large rats through a stomach tube; and in such cases as much as 10 mg. of these were administered at one time. The number of experiments performed on trained animals with the drugs was 124. Both caffeine and adenine were administered in the form of a weak aqueous solution of the bases (0.2 to 0.4%). As a rule, each rat was given the drug not more than once or, at most, twice a week. An effort was made to determine the effects of adenine and caffeine separately and in combination on each individual animal. The results obtained were as follows:

Caffeine was administered to rats in 51 experiments. In 36 experiments (71%), excitement was produced; in 3 experiments (6%), no effect was observed; and in 12 cases (24%), a depression was noted after administration of the drug. Adenine was given in 40 experiments. A slight excitement was noted in 21%, no effect was observed in 28%, and a distinct depression was produced in 52%. When adenine and caffeine were administered simultaneously in equal doses of from 1 to 3 mg. per 100 gm. weight, the following results were obtained.