Thermo-Regulatory Function of Rat Scrotum. I. Normal Development and Effect of Castration. ∗

Abstract

It has been shown that the scrotum of certain mammals has a thermo-regulatory function, 1 , 2 and that if the testes are experimentally placed within the abdominal cavity the germinal epithelium undergoes marked degeneration. 3 , 4 In the ram, bull and boar the scrotum acquires the ability to contract and relax to temperature change as the testes begin the production of spermatozoa, and loses this ability following castration. 3 Further studies on the ram indicated that this function was apparently dependent upon the male hormone. Although the relations of temperature and contractility of the rat scrotum have not been investigated, Hamilton 6 reports that the rat scrotum depends upon male hormone for its development and maintenance and Wells 7 has demonstrated the dependence of the scrotal sac upon male hormone in the ground squirrel.

Procedure. The results of studies of the thermo-regulatory function of 7 normal and 6 castrate albino rat scrota are presented (age 9 weeks to maturity, Table I). Castration was performed at 5 weeks of age through a medial, abdominal incision. The contractility of the scrotum was measured by passing a thread attached to a recording lever through the skin on the ventral surface of the scrotum midway between the scrotal tip and the body; the rats were then anesthetized with nembutal and ether, securely fastened to a heavy animal board, and submerged, with the exception of the head, in a water bath. The temperature of the bath was decreased from 38°C to 20°C at the rate of about 1°C per minute and then raised to 38 °C at the same rate. The scrotal movements were thus recorded on a kymograph.