Oxytocic Activity of Diencephalon and Tuber Cinereum of Normal and Hypophysectomized Rats

Moreno, V. Silva; Croxatto, H.; Aliste, N.; Ampuero, O.

doi:10.1210/endo-57-6-658

Cited by 9 publications

(2 citation statements)

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“…There would thus appear to be considerable evidence in favour of the view that after hypophysectomy the neural stalk or median eminence acquires the ability to hberate antidiuretic hormone. Whether or not oxytocin can be hberated after hypophysectomy does not appear to have been investigated, but recently Moreno, Croxatto, Aliste & Ampuero [1955] have demonstrated that 5-14 days after hypophysectomy in the rat the quantity of oxytocin present in the tuber cinereum is considerably increased. Whether the ability to secrete antidiuretic hormone develops after posterior lobectomy is less certain.…”

Section: Discussionmentioning

confidence: 99%

Lactation in the Rat After Hypophysial Posterior Lobectomy

Benson¹,

Cowie²

1956

Journal of Endocrinology

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Ablation of the posterior lobe of the pituitary in the lactating rat abolished the milk-ejection reflex so that the pups could only be reared if injections of oxytocin were given to the mothers twice daily. When, however, these posterior lobectomized rats became pregnant a second time, parturition was normal and the milk-ejection reflex was sufficiently restored for the rats to rear their litters without oxytocin being administered. The animals, however, continued to exhibit diabetes insipidus. Measurements of residual neurohypophysial tissue showed that hypertrophy of the neural stalk had occurred after posterior lobectomy.These findings are discussed in relation to recent studies on the site of formation and the liberation of posterior-pituitary hormone(s) after hypophysectomy.While the early experiments of Ott & Scott [1911], Schäfer [1913] and Gaines [1915] demonstrated that injections of posterior-pituitary extracts into lactating animals resulted in the ejection of milk, the effect was considered to be of pharmacological interest only. Turner & Slaughter in 1930 appear to have been the first to suggest a physiological role for the posterior pituitary in normal milk ejection, but it was not until 1941 that Ely & Petersen elaborated this theory and emphasized the importance of the milk-ejection reflex in the maintenance of full lactation. Direct evidence, how¬ ever, in support of this role of the neurohypophysis in lactation was somewhat scanty, and Macaulay [1951] in reviewing the literature concluded that there was insufficient evidence available to do any more than suggest that the neural lobe of the hypophysis participated in milk ejection. Within the last 4 years more direct evidence of the role of the neurohypophysis has been obtained. Of particular import¬ ance are the experiments of Cross & Harris [1952], who showed that interruption of the nerve connexions between the hypothalamus and the hypophysis (electrolytic lesions placed in the supraoptico-hypophysial tract) in the lactating rabbit caused a marked diminution in the quantity of milk obtained by the litter in standard suckling tests. If, however, the rabbit was injected with oxytocin the litter then obtained the normal quantity of milk. Studies on the effect on milk ejection of removal of the neural lobe have given somewhat discordant results. Smith [1932] observed that after removal of the posterior lobe normal parturition occurred in the rat and lactation, as evidenced by the growth of the pups, appeared normal or only slightly depressed. Houssay [1935] also reported that bitches could rear their young after 'neurohypophysectomy'. On the other hand, Harris & Jacobsohn [1952] and Cowie [quoted by Folley, 1952] observed that destruction of neural lobe function or removal of the lobe in lactating

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Section: Discussionmentioning

confidence: 99%

Lactation in the Rat After Hypophysial Posterior Lobectomy

Benson¹,

Cowie²

1956

Journal of Endocrinology

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“…Greater than normal antidiuretic activity was found in tuber cinereum extracts obtained from hypophysectomized animals by Sato (1928) and reaccumulation of antidiuretic hormone in the median eminence region 30 days after hypophysectomy was described by Lloyd & Pierog (1955). Similarly, the oxytocic activity of the tuber cinereum of rats has been found to be increased 5-14 days after hypophysectomy (Moreno, Croxatto, Aliste & Ampuero, 1955). Barrnett (1954) has shown that hypophysectomized rats have a greater than normal quantity of histochemically demonstrable disulphide groups in the infundibular stalk after hypophysectomy.…”

Section: Discussionmentioning

confidence: 94%