Nitric oxide modulates elicitation of reflex swallowing from the pharynx in rats.
The pharynx is very important for elicitation of reflex swallowing. The region of the pharynx is innervated by the pharyngeal branch of the glossopharyngeal nerve (GPN-ph). Nitric oxide (NO) plays an important role in various physiological functions. The purpose of this study is to investigate the contribution of NO to reflex swallowing evoked by electrical stimulation of the GPN-ph. Swallowing was evoked in urethane-anesthetized rats by application of repetitive electrical stimulation (10- to 20-microA amplitude, 10- to 20-Hz frequency, 1.0-ms duration) to the central cut end of the GPN-ph or superior laryngeal nerve. Swallowing was identified by electromyographic activity of the mylohyoid muscle. Latency to the first swallow and the interval between swallows were measured. Intravenous administration of N(G)-nitro-L-arginine (L-NNA, 0.6 mg/kg), a nonselective inhibitor of NO synthase (NOS), extremely prolonged latency to the first swallow and the interval between swallows evoked by the GPN-ph. Intraperitoneal administration of 7-nitroindazole (5.0 mg/kg), a selective inhibitor of neuronal NOS, significantly prolonged latency to the first swallow and the interval between swallows evoked by the GPN-ph. Administration of L-arginine (an NO donor, 500 mg/kg) and sodium nitroprusside (an NO releaser, 0.6 mg/kg) restored the suppression of swallowing induced by the NOS inhibitor. Superior laryngeal nerve-evoked swallowing was suppressed by administration of a higher dose of L-NNA (6.0 mg/kg). Swallowing evoked by water stimulation of the pharynx was also suppressed by L-NNA (0.6 mg/kg). These results suggest that NO plays an important role in signal processing for initiation of reflex swallowing from the pharynx.
Kijima
Hiroshi
H
Division of Pediatric Dentistry, Niigata University Graduate School of Medical and Dental Sciences, 2-5274 Gakkocho-dori, Niigata 951-8514, Japan. kijima@fmu.ac.jp
Shingai
Tomio
T
Takahashi
Yoshihiro
Y
Kajii
Yuka
Y
Fukushima
Shin-ichi
S
Taguchi
Yo
Y
Noda
Tadashi
T
Yamada
Yoshiaki
Y
D000818:Animals; D001120:Arginine / Q000494:pharmacology; D003679:Deglutition / Q000502:physiology*; D005930:Glossopharyngeal Nerve; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D019335:Nitroarginine / Q000494:pharmacology; D010614:Pharynx / Q000187:drug effects / Q000294:innervation / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012018:Reflex / Q000502:physiology*
D019335:Nitroarginine; D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase