Effect of prostaglandin F2alpha upon ovulation and LH, FSH and prolactin secretion in chlorpromazine blocked rats.

The ovulation-inducing and LH, FSH and protein releasing activities of prostaglandin F2alpha (PG F2alpha) were investigated, using the female rats which had ovulation blocked by chlorpromazine (CPZ). Serum LH, FSH and prolactin concentrations were measured with NIAMD-rat-radioimmunoassay kits. The number of ova present in the fallopian tubes was investigated microscopically. Subcutaneous injection of 0.4-1.6 mg of PG F2alpha at 3:00 p.m. to CPZ-blocked proestrous rats induced ovulation in 80% of the animals during presumptive estrus. However, the percentage of ovulating rats was reduced in 40-60% of the animals when the same doses of PG F2alpha were injected intravenously. All control animals receiving the vehicle alone did not ovulate. The number of ova was not related to the dose of PG F2alpha, but the percentage of ovulating rats was. The serum LH peak was observed 10 min after the intravenous injection and 60-180 min after the subcutaneous injection of PG F2alpha. The peak in serum FSH and prolactin occurred simultaneously 180 min after both subcutaneous and intravenous injection of PG F2alpha. It is concluded from these data that PG F2alpha at dose levels used, may directly affect the hypothalamo-pituitary axis and consequently induce ovulation. These results further support the conception that the prostaglandins (PGs) have a central effect stimulating LH, FSH and prolactin release from the anterior pituitary.