ABSTRACT
The present research had the objective of evaluating the estrous cycle of female rats kept in the absence of light. The study involved 20 albino rats (Rattus norvegicus albinus) with the age of 40 days old, weighing nearly 150 g. The animals were divided in two groups: Group I- female rats kept in the clear/dark cycle 12/12 h and Group II- female rats kept in the light absence. The animals were kept with regular meals and "ad libitum" water, and at temperature of 22º C. After three months of experiment, the rats were submitted to colpocitologic exams for a period of five weeks consecutively. The smears obtained were dyed through the method of Shorr-Harris and analyzed by light microscopy. Our results showed that in the group I the animals presented larger incidence of the estrus phase with a percentage of 40%, followed by the proestro, diestro and metaestro phases with percentage of 26%, 18% and 16% respectively. In the group II there was a larger incidence of the metaestrus phase, which presented a percentage of 34%, followed by the estrous phase, with 24%. The proestrus and diestrus phases had the same percentage, with 21% of the total of the cycle. However, these results didn’t show statistically meaningful differences. So, we concluded that the absence of light influences directly in the frequency of the estrous cycle phases in rats, leading to a reduction in the incidence of the estrus phase, causing the increase of the estrous cycles in these animals.
KEY WORDS:
Estrus cycle; melatonin; absence light.
Thumbnail
