Recurrence of Estrous Cycles in the Light-Induced Persistent Estrous Rats by Reserpine

Abstract

SynopsisEffect of continuous illumination (LL) on ovarian functions was compared at various ages between the rats exposed to LL from 70 days of age (LL-70) and exposed to LL from the day of birth (LL-0).LL-0 rats retained corpora lutea in their ovaries in higher incidence than LL-70 rats. Effect of reserpine on the restoration of cyclicity was studied in LL-0 and LL-70 rats shortly after they became persistent-estrous.LL-0 rats restored cyclicity in higher incidence than in LL-70 rats.Exposure of adult female rats to continuous illumination brings about persistent estrus which is characterized by prolonged vaginal cornification, failure of spontaneous ovulation and cystic follicular ovaries devoid of corpora lutea (see the review by Reiter and Fraschini, 1969). Ovarian weight and gonadotrophin secretion in these rats were gradually reduced as the exposure time to constant light elapsed (Honma et. al., 1972;Lawton and Schwartz, 1967).However, Takahashi and Suzuki (1969) and Takeo et al.(1974) reported that the rats exposed to LL from the day of birth were not so susceptible to constant illumination in manifestation of persistent estrus as the rats subjected to LL from advanced ages. In the present experiment, ovarian morphology was compared between the rats exposed to LL from 70 days of age and from the day of birth. The responsiveness to reserpine which is believed to modify gonadotrophin secretion (Ganong, 1972) and levels of biogenic amines in central nervous system (Bertler et al., 1956 ;Shore et al., 1955) was also investigated in persistent estrus rats of LL-70 and LL-0. Materials and MethodsWistar female rats were used. To obtain LL-0 rats, pregnant rats were kept in a continuous lighting condition, and the pups were raised in the similar conditions. Adult female rats exhibiting 4-day estrous cycle were transferred to constant light regimen when the animals reached 70 days of age (LL-70). The light source was white fluorescent lamps (about 500-600 lux). Daily vaginal smears since the opening of the vaginal orifice were examined at 10-11 a.m. until the day of sacrifice.Totally 23 of LL-70, 24 of LL-0 and 20 of control (12 hours light-12 hours darkness) rats were sacriries and uteri were weighed. The ovaries were fixed in Bouin's sol., cut in paraffin and stained with hematoxylin and eosin and were examined histologically.Eleven LL-70 and fourteen LL-0 rats which came to show continuous estrus for ten days were injected with reserpine subcutaneously once a day for 2 days. Daily dose of reserpine was 1mg/kg body weight. Eleven rats in both groups were sacrificed 2 to 3 weeks after the first injection of reserpine. Three of LL-0 rats similarly treated were kept for 32-47

Induction of Persistent Estrus by Constant Light: Effects of Neonatal Constant Light and Harderian Gland Function

“…1969], Previous work from our laboratory has shown that rats exposed to LL from the day of birth were less likely to go into persistent estrus compared to rats kept in LL beginning at the 70th day of age [Shirama et a!., 1976a[Shirama et a!., , 1976b. The 1st experiment in this report deals with further studies on the influence of neonatal illumination on the occurrence of LL-induced persistent estrus.…”