[Chemical anatomy of the nociceptive transmission and modulation in the spinal dorsal horn].

The present study had been made to study the distribution and synaptic characteristics of primary afferent C fibers and the normal chemical architecture of some neurotransmitters in spinal dorsal horn. The changes of the neurotransmitters with acute nociceptive stimulation were measured quantitatively. We demonstrated the synaptic relationships among primary afferent C fibers, inhibitory interneurons and nociceptive dorsal horn neurons and discussed their function in nociceptive transmission and modulation. These results provide evidence that acute pain evolved co-release of substance P and glutamate from C-fiber terminals may constitute a driving force for secondary activation of ascending projection neurons or of internal GABAergic antinoceciptive system directly via their receptors in the dorsal horn of the spinal cord.