![]() ![]() Conclusions These effects are consistent with increased rapid-response impulsivity after pharmacological noradrenergic stimulation in healthy controls. Time courses varied effects on blood pressure generally preceded those on metabolites and test performance. Yohimbine-associated increase in plasma MHPG correlated with increased impulsive response rates. On the IMT, yohimbine increased impulsive errors and impulsive response bias and accelerated reaction times. ![]() Yohimbine increased systolic and diastolic blood pressure and pulse rate. Results Yohimbine increased plasma MHPG and VMA but not HVA. Rapid-response impulsivity was measured by commission errors and reaction times on the Immediate Memory Task (IMT), a continuous performance test designed to measure impulsivity and attention. Metabolites of norepinephrine (3-methoxy-4-hydroxyphenylglycol, MHPG vanillylmandelic acid, VMA) and dopamine (homovanillic acid, HVA) were measured by high pressure liquid chromatography with electrochemical detection. Blood pressure, pulse, and behavioral measures were obtained before and periodically after 0.4 mg/kg oral yohimbine or placebo in a randomized, counterbalanced design. Methods Subjects were twenty-three healthy controls recruited from the community, with normal physical examination and ECG, and negative history for hypertension, cardiovascular illness, and Axis I or II disorder. Objective We assessed effects of yohimbine, which increases norepinephrine release by blocking alpha-2 noradrenergic receptors, on plasma catecholamine metabolites, blood pressure, subjective symptoms, and laboratory-measured rapid-response impulsivity. Rationale Rapid-response impulsivity, characterized by inability to withhold response to a stimulus until it is adequately appraised, is associated with risky behavior and may be increased in a state-dependent manner by norepinephrine. Norepinephrine and impulsivity: Effects of acute yohimbine ![]()
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