The Effects of Prenatally Induced Hypothyroidism of the Neural Development and Problem Solving Ability of Maturing Hypothyroid Rats
Barton, Dwayne A.
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The problem. The problem was to yield neonate rats hypothyroid by treating pregnant female rats with propylthiouracil (PTU), and then to evaluate the problem solving ability and the changes in the brain of the hypothyroid offspring. Procedure. Three 8-day sperm-positive female rats were given PTU (0.01 gm/100 ml) water from day 15 of gestation until day 7 postpartum. Two 8-day sperm-positive female rates were controls which were given tap water. Offspring of these female rats were to be the object of the study. However, high neonate mortality required that two additional groups be obtained. One, an all experimental group of 3 females, received PTU (0.01 gm/IOO ml) water from day 5 to day 21 postpartum, and the other, a group of eight 24-day old rats, served as the experimental controls. Intelligence was tested with a Y-maze at 4 weeks of age and 8 weeks of age. At 8 weeks all rats were sacrificed and brains were removed and fixed for histological study. Findings. Experimental rats learned markedly more slowly than did the control rats. Control rats had significantly more Purkinje cells in the cerebellum than did the experimental rats. Conclusions. When compared to controls, rats rendered hypothyroid in utero or neonatally exhibit learning retardation throughout life. The brains of hypothyroid rats show differences in the development of the cerebellum as evidenced by histological examination. Recommendations. Further study with smaller blocks of tissue, electron microscopy, and a different method of tissue preparation should yield data on subcellular changes of nervous tissue, if such changes exist. Another experimental possibility would be to test the motor coordination and equilibrium sense of hypothyroid neonate rats, since a major cerebellar function is motor coordination.
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