Anatomical evidence of regional specific effects of acupuncture on gastric motor function in rats

To obtain the anatomical evidences of possible neural pathways in mediating acupuncture-induced gastric motor responses, we studied c-Fos immunohistochemistry of the brain stem in response to acupuncture in rats. Acupuncture needles were inserted at the bilateral acupoints of ST-36 (lower limb) or ST-25 (abdomen) for 30 min. After acupuncture, the brainstem was removed for c-Fos immunohistochemistry. The total number of c-Fos immunopositive cells was counted in the dorsal motor nucleus of the vagus (DMV), the nucleus tractus solitarius (NTS) and the rostral ventrolateral medulla (RVLM). Acupuncture at ST-36, but not ST-25, significantly increased the number of c-Fos immunopositive cells at the DMV to 6.7 +/- 0.4 cells/section, compared to that of controls (1.7 +/- 0.2 cells/section) (n=5, P<0.05). Acupuncture at ST-25, but not ST-36, significantly increased the number of c-Fos immunopositive cells at the RVLM to 12.6 +/- 0.8 cells/section, compared to that of controls (4.2 +/- 0.7 cells/section) (n=5, P<0.05). Acupuncture at ST-36 also increased the number of c-Fos immunopositive cells at the medio-caudal and caudal NTS. On the other hand, acupuncture at ST-25 increased the number of c-Fos immunopositive cells at the medio-caudal NTS. It is suggested that somatic afferents activated by acupuncture at ST-36 is conveyed to the medio-caudal and caudal NTS and stimulates the DMV neurons. In contrast, somatic afferents activated by acupuncture at ST-25 is conveyed to the medio-caudal NTS and stimulates the RVLM neurons. The RVLM neurons are known as premotor sympatho-excitatory neurons that provide drive to the sympathetic preganglionic neurons in the intermediolateral nucleus of the spinal cord. Thus, acupuncture at ST-36 stimulates gastric motility via vagal efferents, while acupuncture at ST-25 inhibits gastric motility via sympathetic efferents in rats.