RESEARCH ON SECRETORY MECHANISM OF HYPOTHALAMIC

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We inestigated for these two years secretory mechanism of hypothalamic hormones such as somatostatin (SRIF) and Thyrotropin-Releasing hormone (TRH) using method of brain microdialysis, and we now summarize these results.1) In measuring the extremely small amount of hypothalamic hormones by brain microdialysis method, we clarified the usefulness and adequecy of PC and PS membranes.2) Secretory mechanism of somatostain (SRIF) from the hypothalamus : We investigated the SRIF concentration in extracellular fluid in rat pituitary gland. The results were follows : The concentration of SRIF in extracellular fluid of the rat pituitary was between 35 to 97 pg/ml, and it showed the circadian rhythm with higher concentration in the light phase (35-55 pg/ml) than in the dark phase (60-97 pg/ml). Furthermore, SRIF concentration occasionally increased in 3-6 hours-interval. When we investigated the influences of various anesthetic agents, SRIF concetration increased with urethane anesthesia, and it decreased with pentobarbital anesthesia.3) Secretory mechanism of Thyrotropin-Releasing Hormone (TRH) : We investigated the TRH concentration in the paraventricular nucleus in the hypothalamus of the rat. TRH concentration in the dialysate ranged from 7.6 to 10 pg/ml, and it showed higher tendency in the dark phase (2.74 (〕SY.+-.〔) 1/65 pg/ml) than in the light phase (2.15 (〕SY.+-.〔) 1.46 pg/ml).4) From these results, we clarified the possibility and usefulness of measuring hypothalamic hormones directly and with dinamically by using the method of brain microdialysis.Furthermore, we are at present investigating the secretory mechanism of Gonadotropin-Releasing Hormone (GnRH) and Growth Hormone-Releasing Hormone (GHRH).