Brain research
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Diffuse Noxious Inhibitory Controls (DNIC) were investigated in anaesthetized intact rats, with or without p-chlorophenylalanine (pCPA) pretreatment. Dorsal horn convergent neurones responding to both noxious and non-noxious stimuli applied to their excitatory receptive field located on the distal part of the hindlimb, were recorded in the lumbar spinal cord. These cells received A alpha and C fibre inputs as shown by electrical stimulation of their receptive field. ⋯ These results strongly suggest that serotonergic pathways partially involved in DNIC. They are discussed with reference to the descending control systems, originating from the caudal raphé, which modulate the transmission and/or the integration of nociceptive messages at the spinal level. The possible involvement of DNIC and 5-HT mechanisms to the hypo-algesic phenomena induced by hyper-stimulation is also suggested.