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Pituitary Melanocyte-Stimulating Hormone (MSH) After Suckling Stimulus
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1966
Year
Animal PhysiologyPituitary GlandLactationNeurophysiologyAnimal ScienceMedicinePhysiologyNeuroendocrine MechanismEndocrine MechanismGynecologyHypothalamic PeptidePituitary DiseasePituitary MshNervous SystemEndocrinologyPituitary Msh ActivityPituitary Msh ConcentrationPituitary Melanocyte-stimulating Hormone
Pituitary MSH was studied in rats allowed to nurse 1 hr after being isolated from their young for 8 hr. The suckling stimulus on days 7, 10, 14 and 20 of lactation lowered pituitary MSH activity to about 50 % of the prenursing levels. No correlation was found between this effect and the amount of milk obtained by the litter. Because no change in pituitary ACTH took place when it and MSH were simultaneously assayed in the same material, and because blockade of the MSH decrease did not result from previous administration of hydrocortisone (7.5 mg/100 g), it is inferred that the nursing stimulus provoked a decrease in pituitary MSH concentration. Prolactin did not show melanophoredispersing activity nor did it influence the melanophoric effect of pituitary extracts. Oxytocin (1 IU), injected intravenously, did not induce changes in pituitary MSH concentration. In the first 4 hr after suckling, almost no restoration in pituitary MSH activity occurred, but after 8 hr the prenursing levels were attained (Endocrinology78: 522, 1966)