Induction of c-Fos-like protein in the lateral habenular nucleus by persistent noxious peripheral stimulation.

Persistent noxious peripheral stimulation by formalin injection into the unilateral hindpad of anaesthetized rats induced c-Fos-like protein immunoreactivity (c-Fos-LI) in neurons within the lateral habenular nucleus (LHb) bilaterally. Formalin injection after the transection of spinal cords also induced c-Fos-LI in many neurons within the LHb, though the number of labeled cells changed depending on the post-transection period. These results suggest that the LHb modulates nociceptive information, but that it receives nociceptive information via extraspinal pathways as well as intraspinal ascending noxious pathways.