Sperm migration in rats with experimental diabetes insipidus.

Abstract

It is known that the distance covered by spermatozoa between copulation and fertilization is too large to be interpreted by their own flagellation speed (Bishop, 1961). Since there is some evidence that oxytocin is reflexly secreted in response to uterine stimulation at the time of copulation in women (Harris & Pickles, 1953) and in some animals (Bishop, 1961) it is possible that this oxytocin aids rapid sperm transport. However, the amount of oxytocin thus secreted is considered very small and its definite physiological role in this process is still a matter for speculation. There is also evidence that normal fertilization is not impaired in the absence of oxytocin, at least in the rat (Cross, 1959; Gale & McCann, 1961). Since there is no report concerning sperm migration rate as assessed by actual time and numbers in the oxytocin-free condition, this study was undertaken in an attempt to clarify this point. In order to make oxytocin-free animals the experimental diabetes insipidus was induced by the destruction of the median eminence since it is proved that such a condition abolishes the milk ejection responses both to electrical stimulation (Cross & Harris, 1952) and to normal suckling (Gale & McCann, 1961). Forty-six normal rats (150 to 200 g) of Lister strain were used. Bilateral electrolytic lesions were made in the median eminence using a stereotaxic instru¬ ment and de Groot (1959) forebrain coordinates. Cathodal current of 3-0 mA for 30 sec was passed through a glass-insulated platinum electrode left bare at its tip. Daily vaginal smear and urine output were assessed in a metabolic cage after operation. Out of forty-six rats, thirteen operations proved satisfactory, giving a daily urine output of more than 150 ml and only these were used for the study. Since copulation in rats usually takes place at midnight, for the con¬ venience of the experiment the rats were placed in a chamber in which the day and night schedule was entirely reversed—12 hr each. Since the normal oestrous cycle is considerably impaired in most cases after brain operation, hormones were given to the animals some 3 weeks post-operatively so as to