The P50 midlatency auditory evoked potential, a sleep state-dependent
waveform, thought to be generated by elements of the reticular activating system
(RAS), was recorded following surface stimulation of acupuncture points, i.e.
electroacupuncture (EA). Stimulation of three specific acupuncture
points (PC6, HT3, LR3) generally used in the treatment of pain, psychiatric and
sleep disorders, was found to modulate the P50 potential, compared to no
stimulation. The optimal frequency of stimulation was found to be 5Hz, compared
to 60Hz or 100Hz. Stimulation of these points at 5Hz led to a decrement in P50
potential amplitude, suggesting that EA can induce a decrement in arousal
level. Stimulation of three control points (GB34, LI11, SI3) usually
used for the relief of pain, did not lead to significant modulation of the P50
potential. Unilateral stimulation of the three specific points cited was
ineffective in modulating P50 potential amplitude. Repeated episodes of
bilateral EA at the three specific points cited showed additive effects in
decreasing P50 potential amplitude. There were no differences in responsiveness
across race or gender, and EA did not affect P50 potential habituation.
The figure below shows that repeated recordings of the P50 potential do not
change significantly over time, but when repeated episodes of EA at the three
specific points cited was applied for 20 min with 30 min rests in between, the
amplitude of the P50 potential, a measure of level of arousal, decreased
gradually. Repeated EA, therefore, had additive effects.
These results suggest that EA at specific points may be effectively used to
decrease arousal levels, and such an effect could be used as adjunct therapy for
disorders of hypervigilance. These disorders include schizophrenia, anxiety
disorders and depression.