The physiology of parturition in the tammar wallaby Marcopus eugenii (Desmarest 1817)

The literature pertaining to the physiology of parturition in eutherian and marsupial mammals has been reviewed and discussed. No formal study of parturition has been conducted on any marsupial species and the main areas requiring elucidation have been defined. An electromyographic technique for the acute and chronic recording of uterine muscle activity has been developed and applied to the pharmacology of relevant The spontaneous and induced activity of the myometrium have been investigated in pregnancy and the oestrous cycle with the discovery of a pregnancy-specific myometrial inhibitor acting prehormones in the tammar. ferentially on the pregnant uterus. The pregnant uterus also contains an unidentified myometrial stimulant. Endocrinological studies have been conducted and these suggest that fetal cortisol production is involved in the control of parturition in this species, as in many others. Maternal prostaglandin and progesterone levels also appear to influence the timing and execution of parturition and oestrogen has an apparently abort!- facient action. The corpus luteum is dispensible for gestation after embryonic development has been initiated but lutectomy experiments have shown that it produces a substance essential for parturition. Attempts have been made to substitute for the corpus luteum with the hormone relaxin but these have been unsuccessful. Progesterone has been assayed in corpora lutea obtained at various gestational ages. The pattern of progesterone secretion is similar to that observed in most eutherian species with increasing levels up to late gestation and an abrupt pre-partum fall. The results of this study permit the establishment of a working hypothesis for the control of parturition in the tammar and this is presented as a basis for further investigations