DENSITY AND PATTERN OF DOPAMINE D-2-LIKE RECEPTORS IN THE CEREBELLAR CORTEX OF AGED RATS

The pharmacological properties and the anatomical localization of dopa mine (DA) D-2-like receptors were studied in the cerebellum of 3 month s, 12 months, and 24 months male Wistar rats using combined radioligan d binding and autoradiographic techniques with [H-3]-spiroperidol as a ligand. The binding was consistent with the labelling of the DA D-3 r eceptor subtype. The affinity for DA D-2-like receptors was similar in the cerebellar cortex of the three animal groups investigated, wherea s the density of binding sites (B-max value) assessed using convention al radioligand binding techniques was reduced as a function of aging. Light microscope autoradiography revealed the localization of binding sites primarily in the molecular layer and to a lesser amount in Purki nje neurons layer. A loss of binding sites was noticeable with aging i n the grey matter of the cerebellar cortex. It affected primarily the molecular layer. Analysis of radioligand binding data and light micros cope autoradiography suggests that age-related changes of DA D-2-like receptors depend in part by structural alterations of cerebellar corte x and in part by modifications in receptor expression.