AUTORADIOGRAPHIC DISTRIBUTION OF [H-3] PAROXETINE BINDING-SITES IN THE CAT BRAIN

The autoradiographic distribution of serotonin transporter binding sit es in the cat brain was investigated using [H-3]paroxetine, a selectiv e serotonin reuptake inhibitor. High densities of [H-3] paroxetine bin ding sites were found throughout the limbic areas, especially in the a mygdala, hippocampus, entorhinal cortex, midline thalamic nuclei, and in the hypothalamus. Moderate to high densities of binding sites were also observed in the septum, caudate-putamen and substantia nigra. In the brainstem, ail of the raphe nuclei, the periaqueductal gray, the l ocus coeruleus complex, the inferior and superior colliculi, the inter peduncular nucleus, the inferior olivary nucleus, the solitary and dor sal vagal complexes displayed a strong labeling. Low but significant l evels of binding sites were observed throughout the neocortex, especia lly in the superficial layers. Additionally, a noticeable radiolabelin g was detected in the cerebellum, mainly within the granule cell layer . The broad distribution of [H-3]paroxetine binding sites seen in the cat brain corroborates the view that high affinity reuptake of 5-HT re presents a major mechanism regulating serotonergic transmission and ma y interact with a variety of transmitter systems.