Plasma MHPG levels in lactate and isoproterenol anxiety states

Abstract

It has been claimed that an increase in brain noradrenergic activity plays a role in panic disorder and that enhanced noradrenergic activity may be reflected by plasma levels of MHPG. We investigated plasma MHPG levels in panic disorder patients at baseline and during lactate- and isoproterenol-induced anxiety states. These infusions and 5% dextrose infusions were given to 10 panic disorder patients and 9 healthy control subjects. Each subject received all three infusions, double-blind, in random order, and at 1-week intervals. When compared to controls, plasma free MHPG levels in panic patients were not elevated at baseline, during lactate or isoproterenol infusions, at the point of panic, or up to 20 min after the onset of panic. MHPG values were also not elevated in subjects who panicked compared to those who did not. MHPG values were significantly lower in three patients who failed to panic with isoproterenol, but the patient panickers had MHPG values similar to those of controls. Significant correlations between MHPG levels and anxiety ratings were infrequent and could be accounted for by chance alone. These results did not support the noradrenergic model for panic anxiety states induced by lactate or isoproterenol.