Korean J Otolaryngol-Head Neck Surg.  2003 Aug;46(8):627-633.

Normal Distribution of Nitric Oxide Synthase(NOS) in the Inner Ear of Guinea Pig

• Chung WH
• Park SK
• Cho DY
• Hong SH

Abstract

BACKGROUND AND OBJECTIVES
The purpose of this study is to find out the exact distribution of nitric oxide synthase (NOS) in the cochlea and vestibular organ of normal guinea pig. Nitric oxide (NO) is synthesized from L-arginine catalyzed by NOS and it activates the soluble guanyl cyclase that activates cyclic GMP from GTP. These NO/cGMP pathways are involved in the neurotransmission of the inner ear and the regulation of cochlear blood flow in physiological condition. In addition, excess NO is involved in cytotoxicity. MATERIALS AND METHOD: Five normal guinea pigs were used. Antibodies to three isoforms of NOS (nNOS, eNOS, iNOS) were utilized to stain the paraffin sections of cochlea and vestibular organ (crista and maculae utriculi). Staining patterns were compared to previous reports. RESULTS: Neuronal NOS (nNOS) was constitutively expressed in the lateral cochlear wall (stria vascularis, spiral ligament), spiral ganglion, hair cells and supporting cells in the cochlea. In the vestibular organs, hair cells were well expressed. Endothelial NOS (eNOS) was expressed in the vascular endothelium, cochlear lateral wall, basal parts of hair cells and spiral ganglion in the cochlea. Vascular endothelium and nerve fiber including nerve calyx were also prominently expressed. No inducible NOS (iNOS) was identified in any sections. CONCLUSION: Neuronal and endothelial NOS were constitutively expressed in the inner ear of normal guinea pig. This distribution can explain the role of NO in physiologic conditions, which can be used as basic data in studying the role of NO in pathologic inner ear conditions.

Keyword

Nitric oxide; Nitric oxide synthase