Spontaneous nystagmus and gaze-holding ability in monkeys after intravitreal picrotoxin injections.
1. Eye movements were measured in three rhesus monkeys after monocular intravitreal injections of picrotoxin, a gamma-aminobutyric acid (GABA) antagonist. The effects of this drug were tested when the animals were in a completely dark room, when they performed a smooth pursuit task, and when they viewed either a stationary pattern or a full-field optokinetic pattern rotating horizontally. 2. Between 15 and 20 min after the injection, a sustained conjugate spontaneous nystagmus developed in the dark, with the slow-phase movement in the temporal-to-nasal direction with respect to the injected eye. Peak slow-phase velocity ranged from 15 to 45 degrees/s. The nystagmus persisted for at least 1 h but stopped by the next day. 3. In a well-lit room, the nystagmus was completely suppressed, even during monocular viewing with the injected eye. When the lights were turned off, the slow-phase velocity of the spontaneous nystagmus slowly increased to a steady-state level within 70-120 s. 4. Horizontal smooth pursuit eye movements to a 1 degree target light moving in front of the animal +/- 20 degrees to either side of center of gaze at constant speeds were normal. Target speeds ranging from 15 to 60 degrees/s for both monocular and binocular viewing conditions were used. Binocular and monocular optokinetic nystagmus (OKN) to a full-field drum rotating at a constant velocity (5-90 degrees/s) were also normal. The initial pursuit and steady-state components of OKN were measured, as well as the velocity-storage component (optokinetic after nystagmus, OKAN).(ABSTRACT TRUNCATED AT 250 WORDS)
Ariel
M
M
Department of Behavioral Neuroscience, University of Pittsburgh, Pennsylvania 15260.
Tusa
R J
RJ
D000818:Animals; D005133:Eye Movements / Q000187:drug effects*; D005260:Female; D007267:Injections; D008252:Macaca fascicularis; D009760:Nystagmus, Physiologic / Q000187:drug effects*; D010852:Picrotoxin / Q000494:pharmacology*; D011698:Pursuit, Smooth / Q000187:drug effects; D015348:Vision, Binocular / Q000187:drug effects; D015349:Vision, Monocular / Q000187:drug effects; D014822:Vitreous Body
D010852:Picrotoxin