The aim of this study is to investigate the role of the
purinergic receptor P2X3 in the peripheral and central nervous systems during
acupuncture treatment for the
visceral pain of
irritable bowel syndrome (IBS). A total of 24 8-day-old Sprague-Dawley (SD) neonatal male rats (SPF grade) were stimulated using colorectal distention (CRD) when the rats were awake. The modeling lasted for 2 weeks with one stimulation per day. After 6 weeks, the rats were randomly divided into three groups of eight each: (1) the normal group (NG, n = 8); (2) the model group (MG, n = 8); and (3) the model +
electroacupuncture group (EA, n = 8) that received
electroacupuncture at a
needling depth of 5 mm at the Shangjuxu (ST37, bilateral) and Tianshu (ST25, bilateral)
acupoints. The parameters of the Han's
acupoint nerve stimulator (HANS) were as follows: sparse-dense wave with a frequency of 2/100 Hz, current of 2 mA, 20 min/stimulation, and one stimulation per day; the treatment was provided for seven consecutive days. At the sixth week after the treatment, the abdominal withdrawal reflex (AWR) score was determined; immunofluorescence and immunohistochemistry were used to measure the expression of the
P2X3 receptor in myenteric plexus neurons, prefrontal cortex, and anterior cingulate cortex; and, a real-time PCR assay was performed to measure the expression of P2X3
messenger RNA (
mRNA) in the dorsal root ganglion (DRG) and spinal cord. After stimulation with CRD, the expression levels of the
P2X3 receptor in the inter-colonic myenteric plexus, DRG, spinal cord, prefrontal cortex, and anterior cingulate cortex were upregulated, and the sensitivity of the rats to IBS
visceral pain was increased.
Electroacupuncture (EA) could downregulate the expression of the
P2X3 receptor and ease the sensitivity to
visceral pain. The
P2X3 receptor plays an important role in IBS
visceral pain. The different levels of P2X3 in the peripheral enteric nervous system and central nervous system mediate the effects of the EA treatment of the visceral
hyperalgesia of IBS.