Vestibular and optokinetic nystagmus in ketamine-anesthetized rabbits

The aim of this work has been to analyze the modification of vestibular and optokinetic nystagmus in animals after administration of therapeutic doses of ketamine. Three healthy rabbits (two reds and one white), weighing between 2.5 and 3 kg, were submitted to electronystagmography recording. The rabbits, head blocked, were placed on a Tönnies rotatory chair in the middle of a rotatory cylindrical chamber, the internal area of which was covered with 32 black vertical contrasts. All the rabbits underwent rotatory vestibular stimulation by stop test and optokinetic stimulation. After each test and a rest period for the animals, we administered 10 mg/kg of ketamine and performed the same ENG workup. In the first (red) rabbit, we collected eye-movement data at 3 minutes and 40 minutes after the intramuscular injection of a single dose of ketamine (10 mg/kg). In the second (white) rabbit, we performed ENG recording with the animal under anesthesia for the entire time of the test; in the third (red) rabbit, we analyzed the optokinetic response, from the administration of the drug until the end of its effects. Our data highlight the action of the drug on the structures that control the ocular movements and led to the conclusion of the presence of a second feedback integrator.