Role of serotonin in the diffuse inhibitory controls induced by nociceptive stimulation

In the anaesthetized Rat, the entire population of dorsal horn convergent neurones is differentially affected by a noxious stimulus: while exciting the segmental pool, it strongly inhibits the remaining population. The inhibitory effects, which involve supraspinal mechanisms, are reduced to a great extent in parachlorophenylalanine pretreated animals. The role of raphé-spinal serotonergic pathways in nociception is discussed.