Acute effects of tetrahydrobiopterin on the dynamic characteristics and adaptability of of vestibulo-ocular reflex in normal and flocculus lesioned rabbits.
The acute effects of (6R)-5,6,7,8-tetrahydro-L-biopterin (R-THBP) on the dynamic characteristics of horizontal vestibulo-ocular reflex (HVOR) were examined in chronically prepared alert pigmented rabbits. The HVOR gain was measured by 10 degrees-0.1 Hz sinusoidal oscillation of the turntable in darkness. In control rabbits, intramuscular injection of R-THBP (10 mg/kg) induced an increase of HVOR gain by 0.1-0.2, which lasted for 1-3 h. Sustained 10 degrees-0.1 Hz sinusoidal oscillation of the turntable and screen in the reversed direction induced an adaptive increase of HVOR gain by 0.2 in 3 h, which was not affected by applications of R-THBP. In flocculus lesioned rabbits, the HVOR gain reduced by 23%, and applications of R-THBP no longer induced a HVOR gain increase. These experimental observations suggested that the R-THBP affected on the HVOR dynamics within the cerebellar flocculus or its related neural areas.
Nagao
S
S
Department of Physiology, Jichi Medical School, Tochigi, Japan. nagaos@jichi.ac.jp
Kitazawa
H
H
Osanai
R
R
Hiramatsu
T
T
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D001708:Biopterins / Q000031:analogs & derivatives* / Q000494:pharmacology; D002531:Cerebellum / Q000187:drug effects* / Q000201:enzymology / Q000601:surgery; D003714:Denervation; D005133:Eye Movements / Q000187:drug effects; D006162:Guanylate Cyclase / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D011817:Rabbits; D012027:Reflex, Vestibulo-Ocular / Q000187:drug effects*
D000975:Antioxidants; D001708:Biopterins; D009569:Nitric Oxide; D006162:Guanylate Cyclase; C003402:sapropterin