Intraventricular injection of an N-methyl-D-aspartate antagonist disrupts vestibular compensation.

Guinea pigs which had compensated for a unilateral labyrinthectomy exhibited a loss of ocular motor and postural compensation when a 40 or 20 mM concentration of the NMDA antagonist CPP, was injected through a cannula implanted in the IVth ventricle close to the vestibular nuclei. Similar injections of artificial cerebrospinal fluid did not induce loss of compensation. These results suggest that NMDA receptors may contribute to vestibular compensation in the guinea pig.