Neuroprotective effects of TJ-23 (Tokishakuyakusan) on adult rat motoneurons following peripheral facial nerve axotomy

Abstract

We investigated free radical scavenging activity and the possible neuroprotective effect of Tokishakuyakusan (TJ-23) on facial motor nucleus (FMN) motoneurons after peripheral axotomy. In 40 adult rats, the right facial nerve was transected at the level of the stylomastoid foramen. Following axotomy, the effects of TJ-23 on nitric oxide synthase were investigated using NADPH-d histochemistry. FMN motoneurons were counted bilaterally in sections stained with cresyl violet. Rats administered TJ-23 exhibited clear suppression of injury-induced neuronal NADPH-d expression in the ipsilateral FMN when compared to nontreated controls. The number of surviving motoneurons in the ipsilateral FMN was significantly greater among TJ-23-treated rats than nontreated controls on day 56 following axotomy. The present study demonstrates the neuroprotective effect of TJ-23 after peripheral facial nerve axotomy. Antioxidants may have therapeutic potential in traumatic facial nerve dysfunction resulting from head injury, ear surgery, and parotid gland surgery.