ABSTRACT
Objective To investigate the calbindin D\|28K (CB) neurons that receive the visceral nociceptive information in the interstitial nucleus of the spinal trigeminal tract (INV) directly project to the nucleus of the solitary tract (NTS). Methods Triple\|labeled methods of fluorogold (FG) retrograde tracing combined with Fos and CB proteins immunofluorescence histochemistry after formalin stimulating upper alimentary tract. Results Most of FG\|retrograde labeled neurons distributed in the paratrigeminal nucleus (PaV) and the dorsal paramarginal nucleus (PaMd) of INV ipsilateral to the FG injection. About 71^2% of FG\|retrograde labeled neurons contained CB and 31^5% of FG/CB double\|labeled neurons exhibited positive Fos\|immunoreaction in INV.Conclusion The results suggested that a part of neurons containing CB in INV receive the visceral nociceptive information and directly project to NTS. CB neurons might play an important role in transmitting visceral nociceptive information from INV to NTS. [