Hyperalgesia and the reduction of monoamines resulting from lesions of the dorsolateral funiculus.

Unilateral lesions of the dorsolateral funiculus (DLF) in the rat resulted in unilateral hyperalgesia as revealed by a hindpaw withdrawal test to heat. Larger lesions involving the dorsal column and ventrolateral quadrant did not cause hyperalgesia. The levels of 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), noradrenaline (NA) and dopamine (DA) were measured in the lumbar dorsal quadrant using high performance liquid chromatography (HPLC). In hyperalgesic animals DLF lesions caused an ipsilateral reduction of all the amines and a contralateral reduction of 5-HT and NA. This suggests that serotonergic and noradrenergic axons in the DLF give a contralateral innervation. A correlation was sought between the reduction of amine level and the degree of hyperalgesia shown by individual rats on lesioned and unlesioned sides of the cord. No consistent correlation was found with any of the amines.