Learning in relation to hyperthyroidism in the white rat.

Abstract

Preliminary experimentation revealed that thyroxin injected every other day in doses of 0.050 mg. per kg. of body wt. increased heart rate significantly over control (pre-drug) values. The drug employed was Thyroxin Fraction (Squibb). Thyroxin injns. were begun on the exptl. animals 10 days before beginning of training. 17 exptl. animals and 20 litter-mate controls were trained on an enclosed 10-unit U-maze for 41 trials (2 trials per day except for the 1st day, on which only 1 trial was run). Six weeks after training was terminated the animals were again placed on the apparatus for retention tests. No statistically significant differences between exptl. and control groups were found with respect to either learning, retention, or variability.