Prostaglandins (PG’s) of the E, F, A, or B series were infused into a lateral ventricle of the brain of adult male rats, and the efficacy of each PG to stimulate the discharge of LH, prolactin, and TSH from the pituitary gland was determined. PGE2, PGF2α, and PGF2αβ were found to be potent stimulators of LH release. The release was considerably less when PGE1, PGF1β, PGA2 or PGB2 was infused. The basal release of LH was not altered by infusion of PGFlα, PGA1, PGB1, or the control solution. It is suggested that the cis double bond in the 5, 6 position and the 11-hydroxyl group are essential for the LH releasing activity of PG’s and that these functional groups may be of importance for activation of a receptor at the level of the brain. Prolactin secretion was stimulated 6 to 7-fold by the infusion of 5 γg of PGE2, but 20 γg had no stimulatory effect. PGF2β caused a 3 to 4-fold increase in basal plasma prolactin concentration and was the only PG tested other than PGE2 that stimulated prolactin release. None of the PG’s infused intraventricularly affected TSH secretion.
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