Abstract
Acupuncture analgesia caused by low frequency electrical stimulation of the anterior tibial muscle corresponding to the Tsusanli point was abolished by hypophysectomy in rats. The pathway from the acupuncture point to the hypophysis is defined as the acupuncture afferent pathway, and the final region of this pathway has been found in the anterior hypothalamus (AH) . However, in our previous studies, it was proved that, besides finding that the posterior part of the hypothalamic arcuate nucleus (P-HARN) was the initial region of the acupuncture efferent pathway, the medial part of the hypothalamic arcuate nucleus (M-HARN) also displayed acupuncture afferent characteristics. The present study was undertaken to examine relations between the AH and M-HARN in the acupuncture afferent pathway. Acupuncture responding male Wistar rats were used in the experiments discussed here. The pain threshold was estimated from the percent change of tail flick latency. Electrodes were implanted in the brain for electrical stimulation and for fine lesion according to the stereotaxic atlas of König and Klippel. The destruction of restricted regions in both the AH and the M-HARN abolished acupuncture analgesia. Focal electrical stimulation of the AH produced the analgesia that lasted after termination of the stimulation. This is characteristic of the acupuncture afferent pathway stimulation-produced analgesia. Similar analgesia was produced by stimulation of the M-HARN. The analgesia produced by stimulation of the AH was abolished after restricted lesion of the M-HARN. Furthermore, potential was evoked in the M-HARN by stimulation of the AH. From these result, it was concluded that the M-HARN was more rostrally located than the AH in the acupuncture afferent pathway.
