We showed that norepinephrine (NE) in the bed nucleus of the stria terminalis (BSTL) facilitates stress-activation of the HPA axis (Cecchi, 2002). We also showed that, despite enhanced HPA responses, activation of the NE system is deficient in WKY compared to Sprague-Dawley (SD) rats. Chronic intermittent cold stress potentiated both HPA activation and stress-induced NE release in BSTL of WKY rats (Pardon, SFN 2001). Here, we examined the degree to which NE contributes to the elevated HPA response of WKY rats, and what effect sensitization of stress-induced NE release by cold stress has on that response. Adult male SD and WKY rats were implanted with jugular catheters and guide cannulae aimed at BSTL. Half of each strain were exposed to 7 days cold stress (4 hr/day, 4 °C). On the test day, vehicle or the α1-antagonist benoxathian (BNX, 2 nmole/0.2 μl) were injected into BSTL before 30 min acute immobilization stress (n=8-13/group). Repeated blood samples were taken to measure plasma ACTH. In control rats, ...