Rabbits, with monocular vision, were subjected to cause acute alcohol intoxication by intravenous injection of alcohol (1-2g/kg, B.W.), and body position was changes by side-to-side rotation to longitudinal axis(rolling). Characteristics of
positional
nystagmus induced by left side down and right side down, and the effects of intravenous injection and intraventricular injection of methyl scopolamine on positional nystagmus, were observed by means of electronystagmography.
Positional nystagmus was always induced by changing position from immediately after alcohol injection and continued for about 60 minutes. When the position was left side down, the direction of nystagmus (fast component)of left eye was toward
postero-inferior of the head and right eye toward antero-superior. Also when the position was changed to right side down, the direction of nystagmus was opposite to that elicited by left side down. Therefore, there was no close relationship
between
the
direction of nystagmus and the gravitational direction. Bilateral destruction of the vestibular system abolished the positional nystagmus. Intravenous injection of methyl scopolamine reinforced the positional alcohol nystagmus(PAN) but
intraventricular
injection reduced the nystagmus.
These results indicate that the direction of PAN is not related to the gravitational direction, being not consistent to the conventional concept in rabbits. Also scopolamine may act on the central nervous system to reduce the PAN and on the
peripheral
nervous system to reinforce the PAN.
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