The Results of Alpha-Adrenergic Blockade on Some Behavioral and Physiological Effects of Epinephrine

This study was undertaken to test the hypothesis that epinephrine infusion elicits behavioral arousal as a result of systolic blood pressure increase. Eight patients each received 6 epinephrine infusions, 3 preceded by 150 mg. phentolamine and 3 preceded by placebo. Epinephrine alone produced arousal. Phentolamine markedly reduced the epinephrine-induced increase in systolic blood pressure and arousal occurred to a lesser degree than with epinephrine alone. It is suggested that the residual arousal may have resulted from the phentolamine-epinephrine drug combination which caused a severe rise in pulse rate (mean of 122 beats per minute). Serial blood samples were taken for free fatty acids and cholesterol determinations. Phentolamine alone and epinephrine alone were accompanied by an increase in plasma unesterified (free) fatty acids (FFA). When phentolamine preceded epinephrine infusion, a more marked rise in FFA occurred than with either drug alone. Epinephrine elicited a slight, but not significant, increase in cholesterol levels. The results are discussed in relation to alpha- and beta-adrenergic receptor mechanisms.