Using the techniques of multimicropipette and iontophoresis

we observed whether ACh was involved in the cortical descending modulation of Pf neurons in rats. It was shown that the inhibition elicited by stimulation of the sensorimotor area (SmⅠ) was attenuated after microiontophretic atropine and that the nociceptive responses of Pf neurons were obviously reduced by microiontophoretic ACh.Therefore

it suggests that ACh may be considered as one of the neurotransmitters involved in the descending modulation of pain