THE EFFECTS OF SINGLE DOSES OF DEOXYCORTICOSTERONE ACETATE (DOCA) AND CORTISONE ON THE VASCULAR RESPONSE OF FEMALE RATS TO POSTERIOR PITUITARY HORMONES

¹ Department of Physiology, University of Edinburgh

The effects of single doses of DOCA or cortisone, with or without the addition of stilbstrol, on the vascular responses of anæsthetized female rats to vasopressin and oxytocin were studied.

DOCA reduced the sensitivity to the pressor action of vasopressin in all animals. An initial fall in blood pressure always preceded the rise. After DOCA the majority of animals responded to oxytocin with a small fall and then a rise in blood pressure. Cortisone increased the reactivity to vasopressin in all distrous females; during strus (natural or stilbstrol-induced) cortisone like DOCA reduced the sensitivity to vasopressin. The rise in pressure was, except, in the distrous females, preceded by a sharp fall. Most of the cortisonetreated animals responded to oxytocin by a rise usually preceded by a fall in blood pressure. In three females the blood pressure was unchanged after oxytocin, and in a few it fell with no subsequent rise. Animals showing a diphasic response to vasopressin and a pure depressor or a diphasic response to oxytocin were given dihydroergotamine (DHE) and atropine to see how far the responses depended on autonomic nervous activity. With few exceptions after DHE the depressor phase of the response was abolished and the pressor phase regularly potentiated. The main exceptions were cortisone-treated strous rats and three of the six females treated with cortisone and stilbstrol; in these DHE enhanced the depressor phase of the response to vasopressin and oxytocin, and atropine given later caused a further enhancement. The results are discussed in relation to the activity of the autonomic nervous system.

Note:

I would like to thank Dr. Mary Pickford sincerely for her interest and support. This work was financed by a grant made to Dr. Pickford under the United States Air Force Contract AF61 (052-272).