The ontogeny of the laminar distribution of β-adrenergic receptors in the visual cortex of cats, normally reared and dark-reared

Patterns of distribution of β₁ and β₂ adrenergic receptors were examined autoradiographically in slide-mounted sections from the visual cortical areas of 22 developing cat brains, using [¹²⁵I]iodopindolol as the ligand in combination with displacers specific for β₁ and β₂ subtypes of adrenergic receptors. Within visual cortical areas 17 and 18 of adult brains, the density of β₁ and β₂ adrenergic receptors was highest in laminae I-III, lowest in lamina IV, and intermediate in laminae V-VI. For β₁ adrenergic receptors, this laminar distribution was also seen in visual area 19 as well as in the non-visual area 7 that is lateral to area 19. By contrast, the distribution of β₂ adrenergic receptors varied across cortical areas, such that its density was more homogeneous across the laminae in area 19, and decreased in all laminae in area 7. This pattern of distribution in adult brains was already formed at the beginning of the critical period and was not disturbed by dark-rearing.