Effect of 2-buten-4-olide, an endogenous suppressant of feeding, on reproductive function in rats

The effects of 2-buten-4-olide, an endogenous feeding suppressant, on the estrous cycle and LH secretion were studied to determine the influence of this compound on reproductive function. Estrous cycling female Wistar rats were treated ip with 2-buten-4-olide (0, 30 or 100 mg.kg-1.day-1) for 2 weeks. Treatment with 100 mg.kg-1.day-1 delayed the estrous cycle. 2-Buten-4-olide increased the pituitary content of LH (1651.3 +/- 164.4 vs 927.7 +/- 65.1 ng/pituitary; p less than 0.01), and decreased the serum LH level compared with the control level in diestrus (0.16 +/- 0.01 vs 0.26 +/- 0.03 microgram/l; p less than 0.05). However, it did not affect the GnRH content of the mediobasal hypothalamus. The direct effects of 2-buten-4-olide on the pituitary response to GnRH was examined by perifusing the pituitary. Medium containing 2-buten-4-olide (10(-4) mol/l) suppressed the pituitary response to GnRH (2 micrograms/l) (percent increase at 50 min after start of GnRH stimulation: 180 +/- 47 vs 406 +/- 66%; p less than 0.05). These findings suggest that 2-buten-4-olide is involved in the regulation of pituitary gonadotropin secretion directly by suppressing the pituitary responsiveness to GnRH, and that 2-buten-4-olide may play an important role in starvation-induced anestrus.