Nerve structures in Zusanli (ST36) acupoint in rats

Abstract

Acupuncture points (also called acupoints) are locations on the body, which are the focus of treatment with acu­puncture. Acupuncture point (acupoint) `Zusanli` (ST36) is one of most important and most widely used acu­points in humans and animals. Nerve structures of the peripheral nervous system are presumably responsible for some acupuncture effects. The aim of the present study is to examine the nerve structures in tissues in ST36 acu­point. The experiments were carried out on adult male Wistar rats. Samples from ST36 acupoint with size 5x5x5 mm were obtained and sectioned in 5 I¼m or 30 I¼m sections, alternatively. Classical histological techniques of staining were used: HE immunohis­tochemistry for S-100 protein was also used. Free nerve endings, muscle spindles and nerve fibers were observed in tissues in ST36 acupoint. Free nerve endings were seen in the epidermis. In the dermis small nerve fibers and free nerve endings in a palisade manner around hair follicles and sebaceous glands were visualized. The observed nerve fibers in the dermis are in the proximity of small blood vessels. Moreover, smaller nerve fibers were seen in the subcutaneous tissue. Muscle spindles, small nerve fibers and large nerve fibers were also observed deeper, in the muscular layer. The larger nerve fibers in the deep muscular layer were observed in vicinity of large blood ves­sel. The muscle spindles were observed mostly in the proximity of blood vessels and small nerve fibers. The nerve structures (free nerve endings, muscle spindles and nerve fibers) in the tissues of ST36 acupoint in rats were with normal appearance. These nerve structures possibly play a role in the effect of acupuncture via needle-nerve in­teraction.