Localization of Fibroblast Growth Factor-1 in Cholinergic Neurons Innervating the Rat Larynx

Hiroyuki Okano ¹, Ken-ichiro Toyoda ¹, Hitoshi Bamba ¹, Yasuo Hisa ¹, Yutaka Oomura ¹, Toru Imamura ¹, Shoei Furukawa ¹, Hiroshi Kimura ¹ and Ikuo Tooyama ^1*

¹ Molecular Neuroscience Research Center, Shiga University of Medical Science, Otsu, Japan (HO,KT,HK,IT); Department of Otolaryngology-Head and Neck Surgery, Kyoto Prefectural University of Medicine, Kyoto, Japan (HO,KT,HB,YH); Department of Physiology, School of Medicine, Kyusyu University, Fukuoka, Japan (YO); Signaling Molecules Research laboratory, National Institute of Advanced Industrial Science and Technology (AIST), Ibaraki, Japan (TI); Laboratory of Molecular Biology, Gifu Pharmaceutical University, Gifu, Japan (SF)

^* To whom correspondence should be addressed. E-mail: kinchan{at}belle.shiga-med.ac.jp.

Submitted on September 22, 2005
Accepted on 19 May 2006

	Abstract

Cholinergic neurons in the dorsal motor nucleus of the vagus (DMNV) are particularly vulnerable to laryngeal nerve damage, possibly because they lack fibroblast growth factor-1 (FGF1). To test the hypothesis, we investigated the localization of FGF1 in cholinergic neurons innervating the rat larynx by immunohistochemistry using antibodies to choline acetyltransferase of central type (cChAT) and peripheral type (pChAT) as well as tracer experiments. In the DMNV, only 9% of cChAT-positive neurons contained FGF1, and 71% of FGF1-positive neurons colocalized with cChAT. In the nucleus ambiguus, 100% of cChAT-positive neurons were FGF1-positive. In the intralaryngeal ganglia, all ganglionic neurons contained both pChAT and FGF1. In the nodose ganglia, 66% of pChAT-positive neurons were also positive for FGF1, and 90% of FGF1-positive ganglionic cells displayed pChAT-immunoreactivity. Neuronal tracing using cholera toxin B subunit (CTb) demonstrated that cholinergic neurons sending their axons from the DMNV and nucleus ambiguus to the superior laryngeal nerve were FGF1-negative and FGF1-positive, respectively. In the nodose ganglia, some FGF1-positive cells were labeled with CTb. The results indicate that for the innervation of the rat larynx, FGF1 is localized to motor neurons, postganglionic parasympathetic neurons and sensory neurons, but expression is very low in preganglionic parasympathetic cholinergic neurons.

Key Words: FGF, dorsal motor nucleus of the vagus, nucleus ambiguus, cholinergic neurons

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