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Hypericum extract reverses S-ketamine-induced changes in auditory evoked potentials in humans - possible implications
Harald Murck1, Heidi Spitznagel, Michael Ploch
1Lichtwer Pharma GmbH, Berlin, Germany. haraldmurck@yahoo.de
Background:
Auditory evoked potentials (AEP) provide a correlate of cognitive dysfunction in schizophrenia. Both cognitive dysfunction and AEP-characteristics might be related to reduced glutamatergic neurotransmission as induced by glutamate-antagonist like ketamine. Hypericum extract LI160 has demonstrated a ketamine-antagonising effect. We examined whether LI160 reverses changes of a low dose ketamine on AEP in healthy subjects.
Methods:
We performed a double-blind randomized treatment with either 2 x 750 mg LI 160 or placebo given one week, using a crossover design, in 16 health subjects. A test-battery including AEPs, the oculodynamic test (ODT) and a cognitive test were performed before and after an infusion with 4 mg of S-ketamine over a period of 1 hour.
Results:
S-ketamine lead to a significant decrease in the N100-P200 peak to peak (ptp) amplitude after the placebo treatment, whereas ptp was significantly increased by S-ketamine infusion in the LI160 treated subjects. The ODT and the cognitive testing revealed no significant effect of ketamine-infusion and therefore no interaction between treatment groups.
Conclusions:
AEP measures are sensitive means to assess the effect of low dose ketamine. Provided that ketamine mimics cognitive deficits in schizophrenia, LI160 might be effective to treat these symptoms.
