The present work is to determine the concentration of norepinephrine (NE) in rat hypothalamus by linear sweep voltammetry (LSV) using the ultramicrocarbon fiber electrode for study of acupuncture analgesia mechanism.Experiments were performed on 220--250g wistar albino rats. After therat was put on the operation table inserting the fiber electrod into the HVMand other neighbouring nuclei of the rat's brain

then we determined directlythe concentration of NE

in order to observe the change of norepinephrineconcentration before and after electroacupuncture. Vivo is determined every 5minutes for keeping the fiber electrode stablize.