Proposal of an experimental model for the study of polycystic ovaries

In view of the correlation of the circadian system with the estrous cycle in the rat, some investigators have proposed the induction of polycystic ovaries by exposing rats to continuous light. However, there is divergence with respect to time of exposure and light intensity. in the present paper we propose a simple and efficient experimental model for the study of polycystic ovarian physiopathology in rats. Twenty female Wistar rats weighing 200-220 g were initially submitted to a 14-h light/10-h dark cycle. of the animals with regular estrous cycles, 9 were exposed to continuous light (600 lux) for 74 days (group 1) and 6 remained under the initial lighting conditions. A daily vaginal smear was used as indirect evidence for the changes in the estrous cycle. Plasma gonadotropin measurement and histological ovarian analysis showed that 90% of the animals in group 1 developed cystic follicles with the absence of the corpus luteum, despite the lack of reduction in ovarian weight commonly observed under 24-h lghting. This observation may be explained by the reduced time of stress to which the animals were submitted, since polycystic ovarian development occurred within less than 75 days of continuous exposure to 600-lux light, a time relatively shorter than commonly reported in the literature

Effect of clonidine on growth and plasma somatomedin C levels of young rats

To study effects of clonidine on growth and plasma somatomedin C (SmC) lelvels, 42 male Wistar rats aged 28 days and weighing 75 to 105 g were given clonidine (1,5 microng/ml in drinking water), or filtered water alone and were weighed weekly. After 0,4 and 8 weeks, the animals were sacrificed under ether anesthesia, their length was measured and blood was collected by cardiac puncture for measurement of SmC concentration. Growth and the weigh/lengh ratio were lower, and plasma SmC levels (mean ñ SEM) were greater in the treated groups after 4 (616 ñ 44.7 vs 433.2 ñ 39.38 ng/ml, P < 0.01) and 8(595.2 28.3 vs 412.66 ñ 39.01 ng/ml, P < 0.01) weeks of treatment, suggesting that clonidine treatment increased growth hormone secretion. In other experiments, treated showed increased food intake only during the first week of treatment and decreased epididymal fat weight afther 3 weeks (1.412 ñ 0.0536 vs 1.6 ñ 0.1335 mg/100 g body weight, P < 0.01). The results suggest that clonidine acts at the level of the central nervous system involving transitory modulation of food intake, as well as on the regulation of energy metabolism