UNIQUE PROFILES OF THE ALPHA-1-ADRENERGIC, ALPHA-2-ADRENERGIC, AND BETA-ADRENERGIC RECEPTORS IN THE DEVELOPING CORTICAL PLATE AND TRANSIENTEMBRYONIC ZONES OF THE RHESUS-MONKEY

Film receptor autoradiography was used to study the distribution of al pha 1-, alpha 2-, and beta-adrenergic receptors in the occipital lobe of developing rhesus monkeys ranging in age from the 65th embryonic da y (E65) to adulthood (5 years of age). The study shows that each adren ergic receptor subtype has a unique distribution in the cortical plate and transient embryonic zones of the developing cerebral wall. For ex ample, alpha 1 receptors are prominent throughout the proliferative ve ntricular and subventricular zones while alpha 2 receptors in the same zones form three distinct bands interdigitated with three bands rich in beta sites. There are also considerable temporal differences in the emergence of adrenergic receptor subtypes in specific embryonic zones . For instance, the high density of alpha 1 sites in the germinal zone s occurs only in conjunction with intensive proliferative activity. In contrast, beta receptors emerge in these zones after the majority of cortical neurons have been generated. The transient embryonic zones of ten display higher densities of adrenergic sites than the cortical pla te itself. In particular, the subplate zone subjacent to the developin g visual cortex contains the highest density of alpha 2-adrenergic sit es in the cerebral wall throughout all prenatal ages studies. Finally, the regional differences in the density of beta-adrenergic receptors are evident in the subplate zone underlying the prospective striate an d extrastriate cortex before such differences emerge in the cortical p late. The early appearance, unique pattern of distribution, and time-d ependent changes of adrenergic receptors in the transient embryonic zo nes suggest their involvement in the regulation of the cortical develo pment.