Figure 2.

Outline of the experimental design. During pre-treatment, the rats were subjected to (arrows) (1) none or surgical intervention with NX or AdrX, (2) no injection or injection of PBS or hexamethonium or losartan, and (3) injection of PBS or βAR antagonist, in combinations as outlined in Table 1. All rats were subsequently infused with tyramine. Changes in MBP, CO, HR TPR, and cardiac work load (CWL) were recorded from before drug pre-treatment to before tyramine, and every min throughout the tyramine infusion for MBP, CO, HR, and TPR, and from before to the end of the 15-min tyramine infusion for CWL. The effect of NX and AdrX was analyzed by comparing the baselines prior to drug pre-treatment with that in rats not subjected to surgical intervention. Blood for measurement of plasma catecholamines was collected from the femoral artery after the 15-min tyramine-observation period but without discontinuing the infusion.