Brain Res. 2003 Jul; 978(1-2): 136-40.

Electroacupuncture induces the expression of Fos in rat dorsal horn via capsaicin-insensitive afferents.

Uchida Y, Nishigori A, Takeda D, Ohshiro M, Ueda Y, Ohshima M, Kashiba H.

Department of Physiology, Kansai College of Oriental Medicine, 2-11-1 Wakaba, Kumatori, Sennan, Osaka 590-0433, Japan.

Fos is expressed in rat dorsal horn neurons after electroacupuncture (E-acupuncture), but it is unclear which types of afferent fibers are involved in the expression. It is thought that the Fos expression is induced via Adelta afferents rather than C afferents, since the threshold of Adelta afferents to electrical stimulation is much lower than that of unmyelinated ones. Therefore, neonatally capsaicin treated rats lacking many C afferents were examined to clarify this. Fos expression in the dorsal horn after injection of formalin into the hindpaw was severely attenuated by neonatal capsaicin treatment. However, Fos expression after E-acupuncture to the pads of the hindpaw was unaffected by the same treatment. These results suggest that E-acupuncture induces the expression of Fos in the dorsal horn neurons via capsaicin-insensitive afferents, presumably Adelta afferents.