ADRENERGIC AND SEROTONERGIC RECEPTORS IN AGED MONKEY NEOCORTEX

Autoradiography was employed to compare the distribution and density o f adrenergic (alpha 1, alpha 2, and beta) and serotonergic (5-HT1 and 5-HT2) receptors in the neocortex of young adult (3 to 10 years of age ) and aged (>20 years of age) rhesus monkeys. The age-related changes in the density of adrenergic and serotonergic sites were area and laye r specific. A decrease in the density of alpha l receptors occurred on ly in the superficial layers of the somatosensory cortex, whereas the density of (alpha 2 receptors declined in layer I of the prefrontal co rtex and in most layers of the motor and somatosensory regions. The in crease in beta receptors was largely confined to the deep layers of th e motor and somatosensory areas. The density of 5-HT1 sites decreased in mast layers of the somatosensory cortex, while 5-HT2 receptors decl ined in the deep layers of the motor cortex and middle strata of the v isual cortex. Overall, adrenergic and serotonergic receptors were leas t affected in the prefrontal cortex and most compromised in the motor and somatosensory cortex of aged primates.