Development of the A1 adenosine receptors in the visual cortex of cats, dark-reared and normally reared.

The ontogeny of the distribution of the binding sites for [3H]chlorohydroxyladenosine, an A1 adenosine receptor-specific ligand, was visualized autoradiographically within coronal sections of the visual cortical areas of developing cats. In adults, the A1 adenosine receptors were found in all lamina except for lamina IV, and in particularly high concentration within laminas I-III. In brains of kittens 2 months old and younger who were within the critical period for the development of visual neural function, the receptor distribution was less defined and sparser, except that in contrast to adults, it was found in relatively high concentration within lamina VI. Animals dark-reared from birth, so that the critical period was postponed, exhibited an ontogenetic pattern identical to that of the normally reared animals. These results indicate that, at least with respect to ocular dominance determination, A1 adenosine receptors are probably not involved in determining the state of plasticity that is seen during the critical period.