Effects of lactate-induced panic attacks on brain stem auditory evoked potentials.

As the clinical symptomatology of panic attacks may be conceivably related to abnormal brain stem activity, the present study examined the effect of lactate-precipitated panic on brain stem auditory evoked potentials (BSAEPs). The subjects were 27 patients who met DSM-III criteria for panic disorder (Pd), agoraphobia with panic attacks (AgPa) or agoraphobia (Ag). Following drug washout, patients were tested in two separate sessions, in a double-blind randomised controlled design in which each session involved two sequentially ordered BSAEP collection periods - a baseline period with no infusion followed by an intravenous infusion of 5% dextrose in water or 1.0 M sodium lactate (5 ml/kg in 5% dextrose/water) over a 20-min period. Of the 27 patients, 17 were clear responders, reporting panic attacks and self-report changes under lactate similar to those occurring during spontaneous panic. Of the remaining 10 patients, 6 were pseudo-responders, reporting panic symptoms under both dextrose and lactate, and 4 were non-responders. In the clear responders, lactate did not alter electrical events of the BSAEP, but further analysis within the clear responders, comparing AgPa patients with Pd patients, yielded a significant effect with lactate resulting in a prolonged III-V inter-peak interval in the AgPa group. It is suggested that the increased III-V interval in the AgPa group may be reflective of hyperactivity of brain stem noradrenergic nuclei.