Interruption of visual deprivation during development restores the normal density of peptidergic neurons in the rat visual cortex.

We have previously shown that dark rearing moderates the normal decline in the number of somatostatin (SRIF) and neuropeptide (NPY) neurons in the developing rat visual cortex. Thus, cortical areas of visually deprived animals at postnatal day (P) 60 contain consistently more SRIF and NPY neurons than do the same areas of rats reared in normal lighting conditions. In present study animals were reared in darkness from birth to P14, P21, P30 or P60 and then placed in ambient light conditions up to the day of sacrifice (P60 or P90). Counting of immunocytochemically identified SRIF and NPY neurons in all cortical visual areas of these and of undeprived animals, showed that interruption of visual deprivation during both the early or the late stages of postnatal development restores the normal density of the above peptidergic neurons.