[Autoradiographic visualization on the role of central 3H-5-hydroxytryptamine in acupuncture analgesia]

The role played by central 5-hydroxytryptamine (5-HT) in electro-acupuncture analgesia has been studied in rats by means of autoradiography with isotopic tracers 3H-5-HT. The purpose of the present study is to determine the localization of 3H-5-HT in the midbrain raphe nuclei and in the mesencephalon aqueduct as well as periaqueductal gray matter. Parallel experiments were studied by freezing microautoradiographic method and histo-fixative microautoradiographic method. The analgesia effect of acupuncture can be enhanced or lowered by the increment or the decrement of the 5-HT level in the midbrain raphe nuclei and in the mesencephalon aqueduct as well as periaqueductal gray matter. The results of the present experiments show that, when the rats were subjected to electro-acupuncture analgesia. The microautoradiographic intensities of 3H-5-HT both in the midbrain raphe nuclei and in the areas of mesencephalon aqueduct were significantly increased. It may be observed that the release of 5-HT in these regions of the brain is accelerated during acupuncture analgesia. From this it can be concluded that the midbrain raphe nuclei and the mesencephalon aqueduct as well as the periaqueductal gray matter are closely related to acupuncture analgesia. The results imply that 5-HT in these areas may be one of the most important neurochemical agents mediating acupuncture analgesia.