| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1988: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1987: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Research Abstract |
Secretions of prolactin (PRL) and corticosterone (B) induced by the timed suckling decreased rapidly between early and middle and between middle and late stages of lactation, respectively, in rats. The change in PRL secretion was further investigated by tracing the plasma hormone titer at 20-7in inervals throughout 24 hrs on days 5, 15 and 20. Both the incidence of PRL surges in a day and the amount of PRL released at a surge decreased with the progress of lactation, until the surge almost vanished on day 20. Hourly incidence of the PRL surge fluctuated, depicting a clear pattern in a day. Since the surge occurred independently with the suckling by pups, the change in the incidence was considered to follow some internal rhythm(s) of the maternal body.
Experiments using anti-dopaminergic drug and TRH indicated that the depression of PRL secretion with the progress of lactation could not be ascribed to the loss of the ability of pituitary gland to produce and/or to release PRL. Some change(s) in the regulatory mechanism of the hormone release in the hypothalamus and/or somewhere else might occur.
To assess the possibility that depletions of nutrient reserves in maternal body might relate to the declines in PRL and B secretions, effects of starvation, adipectomy and administration of -agonist, isoproterenol, as a potent lipolytic agent, on the hormone secretions were examined. Although milk ejection and then milk production were severely damaged, no appreciable changes occurred in both the amount of nutrient reserves and PRL secretion during the fasting up to 24 hrs, and secretion of B was increased. adipectomy and treatment with isoproterenol brought about slight and significant decreases in PRL release, respectively. Both treatments, however, did not affect the secretion of B. A possibility that some specific relation existed between the change in the fat reserve or fat mobilization and that in PRL release was inferred.
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