title: Basal and stimulated sympathetic responses after epinephrine: no evidence of augmented responses.
abstract: Delayed facilitation of norepinephrine release through the action of epinephrine (NE) at presynaptic beta-adrenoceptors has been postulated to account for the delayed hemodynamic effects of epinephrine and to be a mechanism causally related to the development of hypertension. To determine whether a short-term increase in epinephrine concentrations resulted in subsequent facilitation of sympathetic responses, 9 healthy subjects (age, 21+/-0.9 years) were studied at rest and during physiological stress on 2 occasions when they received an infusion of either saline or epinephrine (20 ng/kg per minute) in random order. Heart rate, blood pressure, forearm blood flow, epinephrine concentrations, and NE spillover were measured at rest, during mental stress (Stroop test), and during a cold pressor test. Measurements were performed before, during the 1-hour infusion of epinephrine or placebo, and 1 hour after the infusion. A radioisotope dilution method was used to measure NE spillover. Hemodynamic measurements and NE spillover were increased during the infusion of epinephrine, but 1 hour after discontinuation of epinephrine there was no significant augmentation of hemodynamic or sympathetic responses. NE spillover 1 hour after saline or epinephrine infusion was similar (0.85+/-0.2 versus 0. 87+/-0.2 microg/min; P=0.92). In addition, there was no delayed facilitation of stress-induced hemodynamic or NE responses after epinephrine. These findings do not support the hypothesis that epinephrine results in delayed facilitation of NE release.
authors.affiliation: Division of Clinical Pharmacology, Vanderbilt University School of Medicine, Nashville, Tenn 37232-6602, USA. michael.stein@mcmail.vanderbilt.edu
authors.forename: C M
authors.initials: CM
authors.lastname: Stein
authors.forename: H B
authors.initials: HB
authors.lastname: He
authors.forename: A J
authors.initials: AJ
authors.lastname: Wood
mesh_terms: D000328:Adult; D004837:Epinephrine / Q000097:blood* / Q000493:pharmacokinetics / Q000494:pharmacology*; D006439:Hemodynamics; D006801:Humans; D008297:Male; D009619:Nociceptors / Q000502:physiology; D012083:Renin / Q000097:blood; D012146:Rest; D016037:Single-Blind Method; D013312:Stress, Physiological / Q000097:blood* / Q000503:physiopathology
chemical_list: D012083:Renin; D004837:Epinephrine