OSMOLAR CHANGES AND NEURAL ACTIVITY IN FROG VESTIBULAR ORGANS

The effects of hypotonic and hypertonic solutions (the normal value wa s 240 mOsm) on posterior canal resting and evoked discharge were studi ed in isolated labyrinth preparations. Hypotonic solutions (60-180 mOs m) were obtained by reducing the perilymphatic NaCl content. Hypertoni c solutions (300-420 mOsm) were obtained by adding to normal perilymph atic solutions suitable amounts of NaCl, glucose, sucrose, glycerol, m annitol and urea. The results demonstrated that any kind of receptor a ctivity was inhibited by hypotonic solutions. On the contrary, hyperto nic solutions produced different effects on resting and evoked activit y. The resting discharge was, with the exception of urea, constantly i ncreased whereas the evoked responses were constantly decreased by all the hypertonic solutions tested. The possible effects of media with c hanged osmolarity in Meniere's patients is also discussed.