GABA expression in c-Fos immunoreactive neurons of the rat periaqueductal gray induced by electroacupuncture at the point of Zusanli

Immunofluorescent investigation of the periaqueductal gray (PAG) was made in the rat receiving electroacupuncture (EA) delivered to the acupoint (AP) called Zusanli (ST36) on the hindlimb. The EA led to strong expression of c-Fos- and gamma aminobutylic acid (GABA)- immunoreactivity (IR) mainly in the ventrolateral to lateral subdivision of the PAG. The double immunofluorescent experiments showed GABA expression in c-Fos immunoreactive neurons in the PAG. Morphometric analysis revealed that the number of double-labeled neurons in the AP case is approximately three times higher than that in the non-AP case. The present findings might indicate that PAG neurons activated by the EA at the AP of Zusanli participate in the descending pain control system of GABA.