Prostaglandins and the Release of LHRH from Hypothalamic Synaptosomes

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Abstract
The possible role of prostaglandins (PG) in the hypothalamic control of ovulation was investigated by studying the effects of indomethacin (ID) and PG on the release of luteinizing hormone-releasing hormone (LHRH) from hypothalamic synaptosomes. Female rats were chronically pretreated with ID on diestrus 2 (D2) and proestrus (P), or on diestrus 1 (D1) and D2. Basal LHRH release from hypothalamic synaptosomes prepared from rats pretreated on D2/P was reduced to 48% after a 20 min incubation period, compared with sham-treated animals. ID pretreatment on D1/D2 caused a similar but less marked reduction in LHRH release (to 66% of controls at 20 min). Extraction of the LHRH remaining within the synaptosomal pellet showed that ID retreatment also reduced the synaptosome content of LHRH. (15S)-15-methyl PGE2(15-E2,10-4 and 10-6 M) added to the incubating medium stimulated the release of LHRH by approximately 40%, but this effect was only observed in synaptosomes prepared from ID-treated rats. PGE2 (10-4 and 10-6 M) had no significant effect in either sham-treated or ID-treated groups.