AUTORADIOGRAPHIC MAPPING OF 5-HT1, 5-HT1A, 5-HT1B AND 5-HT2 RECEPTORS IN THE RAT SPINAL-CORD

The distribution of 5-HT1, 5-HT1A, 5-HT1B and 5-HT2 receptors in the rat spinal cord was investigated with quantitative autoradiography. Receptors were labeled respectively with [H-3]serotonin (5-[H-3]HT),8-hydroxy-2-[N-dipropylamino-H-3]tetralin (8-OH-[H-3]DPAT), [I-125]iodocyanopindolol and [H-3]ketanserin. It is shown that 5-HT1, 5-HT1A and 5-HT1B receptors are distributed within the spinal cord according to a rostro-caudal gradient. Both 5-HT1 and 5-HT1A receptors are mainly present in the dorsal horn and 5-HT1B is present throughout the spinal cord, exhibiting high densities in the caudal-most part of the dorsal horn in lamina X and in the sacral parasympathetic area. On the other hand, 5-HT2 receptors are shown mostly in the thoracic sympathetic area and in the thoracic ventral horn; the dorsal horn exhibits few 5-HT2 receptors. The differential involvement of 5-HT through different receptors in nociception, autonomous nervous system control and motility are discussed.