The attenuation effect of chlorpromazine on electro-acupuncture analgesia: involvement of dopamine system.

The effect of chlorpromazine (CPZ) (0.1 or 0.5 mg/kg, iv) on electroacupuncture analgesia (EAA) was examined by using potassium dolorimetry in rabbits. CPZ itself induced hyperanalgesia, whereas it attenuated EAA in terms of maximal increase of pain threshold as well as EAA after effect. Therefore, CPZ is not a good candidate for enhancing EAA in clinics. Monoamines and their metabolites in cerebrospinal fluid (CSF) of the rabbits were detected by high pressure liquid chromatography coupled to electrochemical detector (HPLC-ECD) method. It was revealed that CPZ enhanced DOPAC and HVA contents in CSF in both the presence and absence of electroacupuncture. CPZ attenuated EAA with elevations of DOPAC and HVA concentration in CSF. There was a positive correlation between the increases of DOPAC and HVA contents in CSF and attenuation effect of CPZ on EAA. These results suggested that activation of dopamine system be unfavorable for EAA.