Effects of Microinjection of Various Prostaglandins into the 3rd Ventricle, Median Eminence and Pituitary on Plasma LH in Rats

The effects of microinjection of PGs (PGE1, E2, F2a) into the 3rd ventricle, median eminence (ME) and anterior pituitary on plasma LH in rats were investigated. Blood samples were obtained by jugular puncture before, and 10 and 45 min after the injection of PGs (50 or 100μg). Plasma LH was measured by radioimmunoassay. In the 3rd ventricle microinjection, PGE2 produced a significant rise in plasma LH. PGE1 and F2a did not significantly alter plasma LH levels. In the median eminence, PGE2 and El produced a significant rise in plasma LH. PGF2a did not alter plasma LH levels. In the pituitary, PGE2 and El produced a significant rise in plasma LH. PGF2a did not alter plasma LH levels. These observations indicate that PGs act directly on the hypothalamic-pituitary axis, and that particular PG may be involved in the release of particular hormones from the hypothalamus and pituitary.