SUBSTANTIAL REDUCTION OF NORADRENALINE IN KITTEN VISUAL-CORTEX BY INTRAVENTRICULAR-INJECTIONS OF 6-HYDROXYDOPAMINE DOES NOT ALWAYS PREVENT OCULAR DOMINANCE SHIFTS AFTER MONOCULAR DEPRIVATION

Ten kittens had cannulas inserted into their lateral ventricles for daily injections of 6-hydroxydopamine (6-OHDA). At 5-6 wk of age 1 eye was sutured shut, and 1 wk later recordings were made from the visual cortex to assay the ocular dominance of a sample of cells. In 6 kittens the injections of 6-OHDA were continued until the day before recording, while in 4 kittens the injections were stopped around the time of eye suture, on the assumption that continued injections of 6-OHDA over several days has effects that are not specific to the noradrenaline (NA) system and that the 2 procedures might show different results. In all animals the concentration of NA in the visual cortex near the site of recording was reduced by .apprx. 90%. In all animals the ocular dominance histograms recorded from the visual cortex were shifted so that the majority of cells (83 .+-. 13%) were dominant by the open eye. There were no substantial differences between the 2 groups of experimental animals or between the experimental animals and 2 control animals that had cannulas implanted and ascorbate alone injected without 6-OHDA. The concentration of NA in the visual cortex can be reduced substantially by injections of 6-OHDA into the lateral ventricle without preventing the shift in ocular dominance that usually occurs after suturing shut the eyelids of 1 eye.