The finding of expression of OTR mRNA by real-time qPCR and proof of OTR staining by immunohistochemistry in all heart compartments indicate that OT and its receptors may have function as a cardiovascular hormone. The differences in the HPA axis activity, as is exemplified in Sprague-Dawley and Lewis rat strain, do not project in the expression of OTR mRNA under basal condition.
The effect of activity of HPA on OTR expression should be studied under stimulated conditions as it was performed in the behavioral studies.