Objective: To investigate the afferent pathways and the relationship between mouth-face region and “Hegu” (LI 4) Point. Methods: ① Biotin labeling: Twenty-four adult Wistar rats

divided into facial area and “Hegu” groups

were anesthetized with 1% sodium phentobarbital 40 mg/kg. Neurobiotin (Nb)(2.0%

20 μL) was injected into the left mouth-face and “Hegu”(LI 4) point regions respectively.72 hours later

these animals under anesthesia were perfused transcardially with saline

then with fixative (1.5% glutaraldehyde and 1.0% paraformaldehyde in 0.1 M sodium phosphate buffer). ② Expression of c-fos: 24 Wistar rats were divided into facial area and “Hegu” groups. Under anesthesia

the left mouth-face and “Hegu” were punctured with acupuncture needles (with two needles being in each point) and stimulated with an electroacupuncture apparatus by setting the stimulating parameters as strength of 5 V

frequency of 100 Hz and duration of 30 min. 1.5～2 hours later

the rats were perfused with the same fixative mentioned above. Spinal cord and lower-brainstem tissues were sliced (30 μm) and then stained with immunohistochemical method. Results: ① Following injection of biotin into facial area

densely labeled fibers were found in the left nucleus of spinal tract of trigeminal nerve (NSTTN) and semilunar ganglion of the trigeminal nerve; light-densely labeled fibers observed in nucleus of the solitary tract (NTS) and reticular formation

and fewer positive fibers seen in the posterior horn of C 1～C 3 of the spinal cord.② The densely labeled fibers from “Hegu” (LI 4) area were found in the posterior horn of C 6

moderate amount of the labeled fibers were seen in C 4～C 5

and fewer seen in cuneate nucleus of the medulla oblongata. ③ After EA stimulation of the left facial area

a large number of fos positive neurons were observed in the ipsilateral NSTTN

moderate number of the labeled cells seen in semilunar ganglion of the trigeminal nerve

NTS and reticular formation of the medulla oblongata

and fewer c-fos positive cells seen in the ipsilateral posterior horn of C 1～C 3 segments. ④ Following EA stimulation of “Hegu”(LI 4)

many c-fos positive neurons were observed in the posterior horn of C 4～C 6

and fewer labeling was seen in cuneate nucleus

NTS and reticular formation of the medulla oblongata. Conclusion: Facial area may have a direct connection with NTS

while “Hegu” point has no direct project to NTS

nevertheless

message of EA of “Hegu” may reach NTS by way of secondary afferent neurons

etc. In short

NTS may play an important role in the integration and convergence of information from the facial area and “Hegu” point.