NMDA receptors are involved in temporal integration in the oculomotor system of the cat

Spontaneous eye movements were recorded before and after a microinjection (0.1-0.2 microliter) of either APV (an NMDA receptor antagonist) or NBQX (a non-NMDA receptor antagonist) into the nucleus prepositus hypoglossi (NPH) of the alert cat. A unilateral injection of APV caused bilateral failure of the horizontal gaze-holding system: in the light, each saccade was followed by a post-saccadic drift. A unilateral injection of NBQX caused no sign of gaze-holding failure; in the light, spontaneous eye movements were unaffected; in complete darkness, a nystagmus with linear slow phases directed towards the injected side was observed. We conclude that NMDA receptors of the NPH neurones are involved in the gaze-holding system.