EVIDENCE FOR THE PRESENCE OF NEUROKININ-1 RECEPTORS ON DORSAL HORN SPINOCEREBELLAR TRACT CELLS IN THE RAT

Dorsal horn spinocerebellar tract cells of adult rats were labelled by retrograde axonal transport with the B subunit of cholera toxin. Sect ions were prepared from lumbar and thoracic spinal segments and incuba ted with antisera which specifically recognise neurokinin-l receptor p rotein and substance P. Labelled cells and immunoreactivity for the re ceptor and substance P were identified by using three different fluoro phores and the relationships between them were assessed in single opti cal sections with three-colour confocal laser scanning microscopy. For ty-eight cells were examined and 23 of them displayed immunoreactivity for the receptor. Many substance P-immunoreactive profiles were prese nt in lamina V and some formed contacts with spinocerebellar tract cel ls possessing neurokinin-l receptor immunoreactivity. The evidence sug gests that substance P may influence the activity of a subpopulation o f dorsal horn spinocerebellar tract cells by acting through neurokinin -l receptors.