Clinical and experimental pharmacology & physiology

The ventral portion of the anterior pretectal nucleus controls descending mechanisms that initiate neuropathic pain in rats.

PMID 25809943


Stimulating the dorsal anterior pretectal nucleus (dAPtN) in rats is more effective than stimulating the ventral APtN (vAPtN) at reducing tail-flick latency, whereas stimulation of the vAPtN is more effective at reducing postoperative pain behaviour. This study examines whether a cell lesion caused by injecting N-methyl-D-aspartate into the dAPtN or vAPtN changes the withdrawal threshold of a rat hind paw during different phases of the tactile hypersensitivity induced by a chronic constriction injury (CCI) of the contralateral sciatic nerve. The number of Fos immunoreactive cells in the APtN was also evaluated. The rats whose vAPtN was lesioned 2 days before CCI had more intense tactile hypersensitivity 2 days after CCI than that of the control group, but the groups were not different 7 days after the CCI. The rats whose vAPtN was lesioned 5 days after CCI had withdrawal thresholds that did not differ significantly 7 days after the CCI. The tactile hypersensitivity of the rats whose dAPtN was lesioned 2 days before or 5 days after CCI was not different from that of the control on the second and seventh days after the CCI. The number of Fos immunoreactive cells in the vAPtN and dAPtN increased 2 days after CCI, but did not differ from that in the control 7 days after CCI. We conclude that vAPtN and dAPtN cells are activated by nerve injury; the vAPtN exerts inhibitory control of the initial phase of neuropathic pain whereas the dAPtN does not appear to exert an inhibitory effect in neuropathic processing.