SYNAPTIC RELATIONSHIPS BETWEEN SEROTONIN-IMMUNOREACTIVE AXONS AND DORSAL HORN SPINOCEREBELLAR TRACT CELLS IN THE CAT SPINAL-CORD

Dorsal horn spinocerebellar tract cells were identified according to e lectrophysiological criteria in adult cats and labelled intracellularl y with horseradish peroxidase. Sections containing labelled neurons we re processed to reveal serotonin immunoreactivity and examined with li ght and electron microscopy. Numerous contacts were observed on cell b odies, and on proximal and intermediate parts of dendrites. Electron m icroscopic examination of contacts revealed that synaptic junctions we re usually present at the region of apposition. It is concluded that s erotonin has a postsynaptic action on dorsal horn spinocerebellar trac t cells and that this action is mediated through conventional synapses .