Increased levels of testosterone have little effect on visual cortex plasticity in the kitten

We tested the hypothesis that increased levels of sex steroids preceding puberty are an important factor in the termination of the critical period for monocular deprivation. Male kittens were injected with Depo-testosterone in order to elevate plasma testosterone to a higher level than that in normal prepubertal male kittens. Control animals did not receive testosterone injections. All kittens were monocularly deprived for 7-18 days, then cells in the visual cortex were examined electrophysiologically, and an ocular dominance histogram was constructed. Treated animals showed an increase in plasma testosterone (1.82-15.16 ng/mL) when compared with the control animals (0.80 +/- 0.25 ng/mL). The fraction of cells driven exclusively by the experienced eye was slightly lower in the treated animals, and there was a slight increase in the dominance of cells by both eyes. However, in both groups of animals, the majority of cells were dominated by the experienced eye, with no significant difference in the weighted parameter used to describe this dominance. In summary, although there is a slight difference between treated and control animals, the results do not support the hypothesis that elevated levels of sex steroids play a crucial role in the termination of the critical period.