The morphology and electrophysiology of the cochlea of the miniature pig.

To report the cochlear morphology and electrophysiology of Chinese experimental miniature pigs. Twenty Chinese experimental miniature pigs were used in this study. Auditory brainstem responses (ABR), cochlear endolymphatic potentials (EP), and the potassium concentrations of cochlear endolymph were recorded. Hair cell morphology was examined using electron microscopy. The capsule of cochlea of the miniature pig has three and one-half turns which contains a 39-mm long membranous labyrinth. The organ of Corti in the labyrinth encompasses three rows of outer hair cells and one row of inner hair cells. The stereocilia of the hair cells in the apical turn of the cochlea were significantly longer than those in the basal turn. The vestibular apparatus consists of three semicircular canals and the otolith organs. The average threshold of the ABR was 35-45 dB SPL (n=20) from 4 to 32 kHz. There was no significant difference in the threshold or latency of the ABR between 1-day-old and 30-day-old miniature pigs. The average EP value was 77.3±14 mV (n=9) and the average potassium concentration was 147.1±13 mM (n=5) recorded from the second turn of the cochlea. These studies on the cochlear morphology and electrophysiology of the miniature pigs help to establish the Chinese experimental miniature pig as an animal model for future studies in otology and audiology.