EFFECTS OF TRANSECTING HYPOPHYSEAL STALKS IN LAYING HENS1

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Abstract
Complete transection of the hypophyseal stalk in laying hens, caused an immediate and unregained loss of body weight, com-plete atrophy of the ovary, oviduct and comb, thus producing a condition closely resembling hypophysectomy as far as gonadal function is concerned. Stalk section did not significantly alter secretion of either thyrotropic or adrenotropic hormones as judged by the normal histology and weight of their target glands, the molting pattern of hens or their ability to withstand sudden temperature changes and prolonged nocturnal fasts. All of these are drastically and negatively affected by hypophysectomy. For these reasons the data presented are thought to support the theory that the rate of secretion and release of the gonadotropic complex in birds is governed by a hypothalamic neurohumor via the portal system. It seems unlikely that the partial hypofunction of the pituitary gland after stalk transection is due to ischemia. The latter should result in panhypopituitarism rather than in the decreased flow of only the gonadotropic complex.