NMDA receptors in frog semicircular canals

The effects of competitive (2-amino-5-phosphonovaleric acid) and noncompetitive (Mg2+, ketamine and kynurenic acid) NMDA receptor antagonists were tested in isolated semicircular canals of the frog. All these antagonists reduced the resting firing rate recorded from the whole ampullar nerve of the posterior canal. This suggests that NMDA receptors are present at the cytoneural junctions between hair cells and afferent nerve terminals in frog vestibular organs.