The effect of acupuncture on locomotor activity was investigated in ra
ts. Stimulation with acupuncture inserted in Bai-Hui point, which is l
ocated at the vertex of the head, increased the spontaneous locomotor
activity of rats measured in ANIMEX meter. This effect was obtained in
rats which received acupuncture significantly at 60 min later as comp
ared with sham-treated control. The sleeping time induced by hexobarbi
tal was also reduced markedly in rats receiving acupuncture. An activa
tion of the central nervous system by acupuncture at Bai-Hui point can
thus be considered. This action was unrelated to opioids because nalo
xone failed to modify it. Increase in locomotor activity was abolished
by an intraperitoneal (i.p.) injection of a-methyl-p-tyrosine (200 mg
/kg) at 2 h before insertion of acupuncture. Deprenyl at the dose suff
icient to elevate monoamine enhanced this action of acupuncture. Media
tion of cerebral monoamines can also be considered. This view was supp
orted by the dose-dependent inhibition of chlorpromazine. Action of ac
upuncture was not observed in apomorphine (0.5 mg/kg, i.p.)-treated ra
ts, probably due to an activated receptor of dopamine. Otherwise, acti
on of acupuncture was enhanced by para-chlorophenylalanine, the deplet
er of endogenous 5-hydroxytryptamine (5-HT), and eliminated by 5-hydro
xytryptophan, the precursor of 5-HT, in the initial stage of insertion
. Participation of 5-HT can be considered as an initial way in rats th
at received acupuncture at Bai-Hui point. These results suggested that
stimulation of Bai-Hui point with acupuncture can activate central ne
urotransmission of monoamines to increase the spontaneous locomotor ac
tivity in rats.