Avian pancreatic polypeptide (APP) immunoreactive neurons in the spinal cord and spinal trigeminal nucleus

Using indirect immunofluorescence technique, avian pancreatic polypeptide (APP) immunoreactive cell bodies and fibres have been observed in the superficial laminae of the dorsal horn of the spinal cord and of the spinal trigeminal nucleus. Fibres were also seen in the ventral horns, in low numbers at the cervical and thoracic levels and in high numbers at the lower lumbar and upper sacral levels. Neither total cord transection, nor dorsal rhizotomy, nor capsaicin treatment seemed to affect the APP systems described above. The present findings suggest that an APP-like peptide may be involved in processing of sensory information at the level of the first relay station.