Model experiments of BPPV using isolated utricle and posterior semicircular canal.
OBJECTIVE
This study was aimed to experimentally investigate the effect of returned otoconia on the utricular using isolated utricles. The effect of interposed otoconia in models of canalolithiasis and cupulolithiasis were also investigated using isolated posterior semicircular canal (PSC).


METHODS
Bullfrogs were used. The utricles (Experiment I) and PSC (Experiment II) were removed in Ringer solution. Experiment I-a: The otoconia were carefully removed from the utricular macula with gentle flush of Ringer solution. Before and after the otoconial removal, sinusoidal rotatory stimulation (0.1 Hz, 135 degrees ) was given to record utricular compound action potentials (CAPs). Experiment I-b: (1) Instantaneous changes in the utricular potentials when the otoconial mass was positioned on the macula were recorded. (2) Utricular CAP changes in response to sinusoidal rotation immediately and 10 min after the otoconial positioning were recorded. Experiment II: PSC CAPs due to sinusoidal rotatory stimulation in normal specimen, canalolithiasis and cupulolithiasis models were recorded.


RESULTS
Experiment I-a: The utricular CAPs in response to sinusoidal rotation showed sinusoidal oscillation. However, this oscillation disappeared after the otoconial removal. Experiment I-b: (1) The utricular potentials transiently increased for 3-4 s after positioning the otoconial mass. (2) The utricular CAPs increased in seven specimens and decreased in four. Ten minutes after the CAPs were almost the same as immediately after otoconial positioning. Experiment II: In cupulolithiasis model, the PSC CAPs decreased in all specimens.


CONCLUSIONS
The otoconia played an essential role as a transducer of acceleration to the utricular macula. Otoconia returned to the utricular macula change utricular reactivity and hence are the possible cause of dizziness after physical therapy. PSC responses to sinusoidal rotation were suppressed in cupulolithiasis model.
Inagaki
Taro
T
Department of Otolaryngology, Tokyo Medical University, Tokyo 160-0023, Japan. QUE07470@nifty.com
Suzuki
Mamoru
M
Otsuka
Koji
K
Kitajima
Naoharu
N
Furuya
Masayoshi
M
Ogawa
Yasuo
Y
Takenouchi
Tsuyoshi
T
D000818:Animals; D004195:Disease Models, Animal; D009759:Nystagmus, Pathologic / Q000503:physiopathology; D010037:Otolithic Membrane / Q000033:anatomy & histology; D011892:Rana catesbeiana; D012444:Saccule and Utricle / Q000033:anatomy & histology*; D012665:Semicircular Canals / Q000033:anatomy & histology*; D014717:Vertigo / Q000503:physiopathology