The induction and potentiation of c-Jun and c-Fos expression in spinal neurons mediated by NK1 and NK2 receptors

Specific antagonists were used to determine NK1 and NK2 receptor mediation of the expression of c-Jun and c-Fos inducible transcription factors. (ITFs) in dorsal horn neurons. The induction of c-Jun by C-fiber stimulation was strongly reduced in the superficial laminae by NK1 and NK2 antagonists, but only weakly in the deep laminae by NK2 antagonism, c-Fos induction was reduced in all laminae by both NK1 and NK2 antagonism but less than with c-Jun. The potentiation of c-Jun expression, caused by a preceding stimulus, was abolished in ail laminae by NK1 and NK2 antagonists, whereas that of c-Fos was reduced in all laminae but again less than that of c-Jun. Thus, the expressions of ITFs mediated by NK1 and NK2 receptors are complex, depending upon the neurons and stimulus considered, and they are not a measure of the neurons' electrophysiological responsiveness.