title: Simulation of cupulolithiasis and canalolithiasis by an animal model.
abstract: The physical mechanisms responsible for cupulolithiasis and canalolithiasis have been investigated by two groups of experiments in isolated posterior semicircular canal (SCC) of frog (Rana esculenta L.). First, clouds of 10-30 isolated otoconia were let to fall (snowfall of otoconia) either through the ampulla onto the cupula, or inside the long arm of the canal, opposite to the cupula. Second, microspheres ranging 30 to 350 microm in diameter were gently moved to and fro inside the long arm of the canal by a micromanipulator. The effects were evaluated by recording the firing rate (Nfr) of the ampullary nerve. Snowfall of otoconia produced detectable changes of Nfr only when otoconia got in contact with the cupula, but not when falling through the endolymph. Movement of the microspheres in the canal long arm induced Nfr changes only if the microsphere diameter exceeded about 50 microm. Although the exact microsphere size needed for receptor stimulation may depend on the experimental conditions, these results strongly suggest that debris moving inside a SCC (canalolithiasis) can produce transcupular pressures able to stimulate ampullar receptors only if they have suitable size, whereas isolated otoconia cannot, except when lying on the cupula (cupulolithiasis).
authors.affiliation: Department of Physiological and Pharmacological Sciences, University of Pavia, Pavia, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Valli
authors.forename: Laura
authors.initials: L
authors.lastname: Botta
authors.forename: Gianpiero
authors.initials: G
authors.lastname: Zucca
authors.forename: Stefano
authors.initials: S
authors.lastname: Valli
authors.forename: Angelo
authors.initials: A
authors.lastname: Buizza
mesh_terms: D000818:Animals; D002137:Calculi / Q000503:physiopathology; D004195:Disease Models, Animal; D004710:Endolymph / Q000187:drug effects / Q000502:physiology*; D005260:Female; D054777:Hair Cells, Ampulla / Q000502:physiology*; D066298:In Vitro Techniques; D020347:Lithiasis / Q000150:complications* / Q000503:physiopathology; D008297:Male; D010037:Otolithic Membrane / Q000502:physiology; D052638:Particulate Matter / Q000009:adverse effects; D011434:Proprioception / Q000502:physiology; D011893:Rana esculenta; D012665:Semicircular Canals / Q000503:physiopathology*; D014717:Vertigo / Q000209:etiology* / Q000503:physiopathology
chemical_list: D052638:Particulate Matter