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Effect of the Electrical Stimulation of the Hypothalamus on the Neurohypophysis of Rabbits

1955; Volume: 8; Issue: 4 Linguagem: Inglês

10.1679/aohc1950.8.517

0004-0681

Masao Okada,

Biochemical effects in animals

Histological changes in the neurohypophysis induced by the electrical stimulation of the hypothalamus of mature rabbits were observed by means of GOMORI's chrome-alum hematoxylin phloxin, HALMI's aldehyde-fuchsin and silver impregnation methods, and the results were as follows:In control animal, the neurohypophysis is entirely filled up with a lot of neurosecretory granules in various size, and more or less contain droplets. Especially there are many granules around the vessels and also in that part in contact with pars intermedia, conversely they are few in the‘Zwischenstreifen’. In silver-staining preparations it seem that those granules are drawn up along the nerve fibre.In case of stimulation of the ventromedial hypothalamic nucleus, the number of neurosecretory granules shows remarkable diminution, especially around the vessels, with the diminution of the droplets simultaneously. The curve of their number is lowest 5 minutes after stimulation, later ascends gradually to normal level as the time passes 20min., 40min., 60min., and then the number exceeds over that of the control number after 90min.In case of stimulation of the lateral hypothalamic nucleus, the number of neurosecretory granules becomes somewhat more than of the control. However, the granules gather around the vessels, but on the other hand in‘Zwischenstreifen’it decreases. And the size of droplets becomes smaller. These changes become clearly observable immediately after the stimulation and usually after 5 minutes. Moreover, as the lapse of time of 20min., 40min., 60min. and so on, the number of the granules decreases to the normal level.According to the finding mentioned above, we think that, in case of sympathetic stimulation of ventromedial hypothalamic nucleus, the neurosecretory material is transmitted into the blood, while, in case of parasympathetic stimulation of lateral hypothalamic nucleus, the excreation of the material is inhibitted.