533. Intramammary pressure changes in the lactating sow: I. The effect of oxytocin

Abstract

Using an electronic pressure recording system, pressure changes in the sow's mammary gland in response to injections of oxytocin and whole pituitrin have been recorded. The results suggest that an injection of oxytocin within physiological range may pass round the circulatory system twice, resulting in a small secondary pulse of pressure. Slow injections over periods of the order of 8–16 sec. are shown to produce a double rise in pressure, the two phases of which are of the same order of magnitude, suggesting a contraction followed by a period of relaxation and a further contraction.