Corpus luteum progesterone secretion in rats undergoing pineal-mediated reproductive regression

In nonseasonal breeders, such as the laboratory rat, the potentiation of the antigonadal action of light deprivation by olfactory bulbectomy is manifested, among other things, by a diminished secretion of testosterone in males and estradiol in females. Little is known about the actions of the pineal gland on progesterone secretion. Since secretion of the luteotrophic hormones (LH and PRL) decreases in blind-anosmic rats and because the rat corpus luteum exhibits different degrees of LH and/or PRL dependency, the purpose of these experiments was to study the corpus luteum progesterone secretion in both pseudopregnant and pregnant blinded-bulbectomized rats. Female rats blinded and bulbectomized at the age of 25 d showed at adulthood (75 d old) (1) estrous cycles longer than the regular 4-5 d in length exhibited by intact rats: 82.3 vs. 9.0% (P less than .01); (2) a decreased paired ovarian weight, 24.1 +/- 3.7 (nine) vs. 37.3 +/- 2.2 (ten) mg/100 gm BW (P less than .05), and lower plasma levels of LH on metestrus: 15.9 +/- 1.7 vs. 26.2 +/- 3.4 ng/ml (P less than .01). Pinealectomy, as previously reported, completely reversed the effects of dual sensory deprivation. In contrast to the clear antigonadal action of the pineal gland, which seems to affect the follicular component of the ovary through modifications in the rate of LH secretion, the production of progesterone by the corpus luteum remained almost unaffected. Although the duration of the diestrous phase in both pseudopregnancy and pregnancy was significantly longer in blind-anosmic rats than in intact ones (P less than .01), the serum levels of progesterone throughout both corpus luteum phases were identical.(ABSTRACT TRUNCATED AT 250 WORDS)