Effect of the retroauricular galvanic stimulation on the central vestibular system: —immunohistochemical evaluation of GABA—

Abstract

The changes of the neurotransmitter (GABA) distribution in the brain stem of the rats by retroauricular galvanic stimulation were investigated using immunohistochemical method. Twenty-one rats were divided into two groups: the control group which received no galvanic stimulation, and the galvanically stimulated group which received anodal galvanic stimulation (unipolar monoauricular, 5mA in intensity, 500msec of duration, 1Hz in frequency) for 30 minutes. The specimens obtained as usual strict procedure for histological investigation were stained immunohistochemically using antisera against GABA. The results were as follows: 1. In the control group, GABA-like immunoreactivity was observed in all four main vestibular nuclei. In the superior, medial, and descending vestibular nuclei GABA-like immunoreactivity was found in the small cells and the terminals. Giant cells in the lateral vestibular nucleus were surrounded by GABA immunoreactive terminals. 2. In the galvanically stimulated group GABA-like immunoreactivity showed recognizable laterality in the lateral vestibular nucleus where GABA-like immunoreactivity surrounding giant cells showed more intensive on the side ipsilateral to the stimulation compared with the opposite side. On the other hand GABA-like immunoreactivity showed no laterality in the superior, medial, and descending vestibular nuclei. 3. It can be concluded that the retroauricular galvanic stimulation cause some changes in the inhibitory activity of the lateral vestibulo-spinal tract and of the spinal motor neuron. © 1990, The Oto-Rhino-Laryngological Society of Japan, Inc. All rights reserved.