Cell size changes in the lateral geniculate nuclei of normal and monocularly deprived cats treated with 6-hydroxydopamine and/or norepinephrine.

Given the proposed role of catecholamines in controlling cortical plasticity in the cat (Kasamatsu, T., J. D. Pettigrew, and M. Ary (1979) J. Comp. Neurol. 185: 163-182), we were interested in whether evidence of such control also could be found in the dorsal lateral geniculate nucleus. We undertook geniculate cell size measurements in 26 normal or monocularly deprived cats, 23 of which had been used in cortical recording studies concerned with catecholamine-induced plasticity. For animals grouped according to experimental treatments, the results can be summarized as follows: (1) in visually normal animals, neither intraventricular injections of 6-hydroxydopamine (6-OHDA) nor local perfusions of norepinephrine (NE) cause changes in geniculate cell size. (2) In otherwise untreated kittens, 1 week of monocular deprivation begun in the 6th week of life results in quite obvious changes in geniculate cell size. (3) Intraventricular injections of 6-OHDA do not appear to prevent deprivation-induced changes in geniculate cell size. (4) Older NE-treated kittens and adult cats that are monocularly deprived for a brief period either late in the critical period or after the critical period has ended do not show deprivation-induced changes in geniculate cell size in either hemisphere. (5) In younger kittens which had been first injected with 6-OHDA intraventricularly and then monocularly deprived for a brief period early in the critical period, there is no evidence to suggest that a local perfusion of NE enhances deprivation-induced changes in geniculate cell size.