Objectives: The aim of this study was to investigate the effect of acupuncture to the acupuncture point HT7 (Sinmun) on morphine-induced behavioral sensitization and the neuronal changes in nucleus accumbens and striatum in rats.
Methods: Male Sprague-Dawley rats were given repeated injections of morphine hydrochloride for 5 days followed by 3 day withdrawal and one challenge injection. The acupuncture treatment was performed for 1 minute once a day for 3 days of withdrawal period and its effect on morphine-induced changes of locomotor activity and Fos expression was examined.
Results: The acupuncture stimulation to HT7 significantly suppressed the morphine-induced increases in the locomotor activity and Fos expression in the nucleus accumbens and striatum, as compared to the controls of non-acupoint or the acupoint on other meridian.
Discussion: These results demonstrated that the inhibitory effect of the acupuncture stimulation to HT7 on morphine-induced behavioral sensitization was closely associated with the suppression of dopamine biosynthesis and its activity in the post-synaptic neurons in nucleus accumbens and striatum. It means that the behavioral effect of the acupuncture can originate from the modulation of the same neuronal mechanism in the central dopaminergic system as in the morphine-induced behavioral sensitization. This modulation was also strictly confined to the stimulation of the specific acupoint, because the stimulation to other acupoint (TE5) on another meridian did not show the modulating effect despite being relatively close to each other. It can be therefore suggested that the acupuncture stimulation has an acupoint-specific property, and might be a useful therapeutic alternative with few side effects for treating morphine addiction.