Effect of intraventricular injections of brain isoantibodies on learning

Abstract

The present method of assessing the effects of anti-brain isoantibody on learning involves multiple slow intraventricular injections of serum γ-globulin (IgG) into the lateral ventricles of chronically prepared unanesthetized subjects. Injections of 80 μl of normal rat IgG on the 8 days preceding training had no adverse effect on the abilities of the subjects to learn a visual discrimination problem. Such trained subjects also performed at criterion after they received an additional intraventricular injection of normal IgG on the day they reached criterion. In contrast, subjects that had received anti-brain IgG before training performed below criterion after they received an intraventricular injection of normal IgG on the day they reached criterion. Subjects that received intraventricular injections of immune IgG prepared from the sera of rats that had been immunized with the microsomal fraction of rat brain (RB F-III) or rat liver (RL F-III) required a statistically significant larger number of trials to learn a visual discrimination problem than control subjects that received normal rat IgG. The anti-RB F-III IgG had a more widespread effect than the anti-RL-F-III in that it produced subjects with statistically significantly higher latencies, poorer memories, and an unusual behavioral trait tentatively called “spinning”. The effect of the anti-RL F-III is believed to be due to its reaction with species-specific antigens in the brain whereas the more deleterious effect of the anti-RB F-III IgG is thought to be due to its reactivity with both species-specific and organ-specific antigens in the brain. The present experiments have confirmed and extended the results obtained earlier with actively immunized subjects.