LACK OF DIRECT EFFECT OF HYPOPHYSECTOMY AND GROWTH HORMONE ON POSTNATAL RAT BRAIN MORPHOLOGY

An investigation was carried out to determine the effects of early hypophysectomy (5-6 days of age) and later hypophysectomy (28 days of age) on brain morphology. Graded doses of growth hormone were injected into normal postnatal rats to compare the brain anatomy with that from the early hypophysectomized rats. The animals were divided into five groups as follows. Group I: The rats were hypophysectomized at 5 days of age and killed at 26 days of age. Replicable somatosensory cortical depth differences were not obtained, possibly due to variation in hypophysectomy techniques. The occipital cortex was not affected by hypophysectomy in these series of experiments. Group II: Littermate rats were hypophysectomized at 6 days of age and killed at 41 days of age. The somatosensory cortex of the hypophysectomized rat was significantly deeper than the control, the difference being attributed to altered skull development. Group III: Rats were hypophysectomized at 28 days of age and killed at 77 days of age. No brain changes were noted, though marked body weight differences were evident. Group IV: Twenty-one micrograms of growth hormone were injected into normal rats in graded weekly doses beginning at 7 days of age and continuing for 3 weeks. No brain changes or body weight differences were found when compared with uninjected controls. Group V: A total of 300 μg was divided into graded, daily injections, beginning at 7 days of age and continuing for 3 weeks. No brain changes or body weight differences were seen when compared with uninjected controls. © 1969.