Strabismus induces an abnormal pattern of alternating
light and dark columns of cytochrome oxidase (CO) activity
in macaque striate cortex. This pattern may arise because
visual perception is suppressed in one eye to avoid diplopia.
To test whether CO activity is reduced in the ocular dominance
columns of the suppressed eye, we performed monocular enucleation
to co-label the ocular dominance columns with Zif268 immunohistochemistry
in seven exotropic adult Macaca fascicularis.
This approach was unsuccessful, for two reasons. First,
Zif268 yielded inconsistent labelling, that was usually
greater in the enucleated eye's ocular dominance columns,
but was sometimes greater in the intact eye's columns.
Therefore, Zif268 was not a reliable method for identifying
the ocular dominance columns serving each eye. Second,
in three control animals we found that a brief survival
period following monocular enucleation (needed for Zif268
levels to change) was long enough to alter CO staining.
For example, a survival time of only 3 h was sufficient
to induce CO columns, indicating that the activity of this
enzyme fluctuates more rapidly than realized previously.
Independent of these findings, we have also discovered
that acute monocular enucleation produces a vivid pattern
of ocular dominance columns visible in unstained or CO-stained
sections under dark-field illumination. The ocular dominance
columns of the acutely enucleated eye appear dark. This
was verified by labelling the ocular dominance columns
with [3H]proline. Dark-field illumination
of the cortex after acute monocular enucleation offers
a new, easy method for identifying the ocular dominance
columns in macaques.