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INHIBITION OF THE RELEASE OF THE NEUROHYPOPHYSIAL HORMONES OF RATS BY CATECHOLAMINES, IN VITRO
Author(s) -
Yeo BK,
Lockett Mary F,
Heller H
Publication year - 1972
Publication title -
australian journal of experimental biology and medical science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.999
H-Index - 104
eISSN - 1440-1711
pISSN - 0004-945X
DOI - 10.1038/icb.1972.45
Subject(s) - phentolamine , endocrinology , medicine , oxytocin , vasopressin , hormone , chemistry , in vitro , hypothalamus , posterior pituitary , inhibitory postsynaptic potential , pituitary gland , biology , stimulation , biochemistry
Summary Superfused horns of uteri removed from rats during artificially induced oestrus were equally sensitive to oxytocin and vasopressin when the superfusion fluid contained MgSO 4 .H 2 O, 500 mg/l. This preparation was used to assay the total neurohypophysial hormone released by pairs of posterior lobes of rat pituitary glands in serial 20 minute incubations in vitro . The rate of release of posterior lobe hormone remained constant from the 20th to the 80th minute of incubation in medium containing 500 mg MgSO 4 .H 2 O per l. The release rate varied from gland to gland: each pair of glands, therefore, necessarily provided its own control for tests of drug action on release rate. L‐noradrenaline and L‐adrenaline (3 × 10‐ 6 M) inhibited the release of hormone from the neural lobes: the α‐adrenergic blocking agent phentolamine, 5·3 × 10‐ 6 M, may have decreased the resting rate of release of hormone and clearly enhanced the inhibition of release caused by noradrenaline. The β‐blocking agent proprannlol (6·8 × 10‐ 6 M) did not influence the basal rate of hormonal release but potentiated the inhibitory effect of noradrenaline.