Effect of testicular temperature on vasomotion and blood flow

Vasomotion (spontaneous rhythmic variations in blood flow) has been demonstrated in the parenchyma of the testes of anaesthetized rats, using a laser-Doppler flow probe. As the temperature of the testis was increased, mean blood flow showed no change, but the frequency of vasomotion increased and its amplitude decreased, until vasomotion disappeared between 36 degrees C and 42 degrees C. As the testis was then cooled, vasomotion reappeared, and increased in amplitude and decreased in frequency as the temperature fell. In control rats, in which the temperature of the testes was maintained at normal scrotal temperature of about 33 degrees C, there no changes in vasomotion over an equivalent period. In both groups of rats, when the temperature of the testes was then allowed to fall below normal scrotal temperature, the amplitude of vasomotion increased and its frequency decreased even further, without any change in mean blood flow. Capillary blood flow was also measured with microspheres at the end of the experiment, when testicular temperature was between 19 degrees C and 27 degrees C, and there was no difference between the cooled and control testes or epididymides.