Under specific environmental conditions, endogenous opioids may selectively influence affective and behavioral processes in that opioid release can attenuate the effects of aversive stimuli. The activation of endogenous opioids associated with increases in blood pressure may serve to attenuate the effect of chronic aversive events and thus contribute to the learning and/or maintenance of essential hypertension, much as predicted within a negative reinforcement paradigm. Seven (unmedicated) hypertensives and seven normotensive controls were evaluated at rest, during a cognitive stressor (mental arithmetic task), and at three subsequent points during the post-stress phase. Dependent measures included systolic and diastolic blood pressures, heart rate, plasma Beta-endorphin levels (derived via radioimmunoassays of venous blood samples), and patient self-reports of subjective discomfort. Baseline, stress, and post-stress blood pressures were significantly higher among hypertensives than normotensives. Systolic blood pressure and heart rate significantly increased from baseline to stress in both groups. At baseline, the mean plasma Beta-endorphin level was significantly greater for the hypertensive group than that for the normotensive group. As a group, hypertensives demonstrated a significant decrease in Beta-endorphin level (well below baseline) following stress, while the normotensive group showed a slight increase
