Gonadotrophin Secretion in Relation to Oestrus and to Ovulation

Abstract

One of the main prerequisites of any detailed study of the interrelated, mutually dependent factors controlling ovulation, is an accurate model for the timing of the various sequential events that occur. Further, in selecting a suitable female mammal to study, it is most desirable that she should have some readily observable or detectable, physiological event from which these sequential events can be accurately timed. In induced ovulators the time of coitus can be used as a marker for timing such events as ovulation, but in spontaneous ovulators the accurate timing of ovulation is sometimes very difficult, primates are a case in point. In some animals such as the rat, the timing of ovulation can be standardized by keeping the experimental animal in a controlled environment of which the duration of light and of darkness are probably the most important single factors (Everett, Sawyer and Markee, 1949). Under such conditions the timing of certain of the immediate pre-ovulatory events in the rat can be predicted with some precision. One of the events which might merit more careful study in the rat is the more accurate timing of when copulation first occurs under the standard conditions of 14 h daylight and 10 h darkness.