Galanin-like immunoreactivity in capsaicin sensitive sensory neurons and ganglia.

In rats treated with capsaicin (CAP) as neonates, galanin-like (GA) immunoreactivity is markedly decreased in the trigeminal ganglion and the dorsal root ganglia as well as in the superficial layers of the dorsal spinal cord (laminae I and II), the substantia gelatinosa, the nucleus and tractus of the spinal trigeminal nerve and the nucleus commissuralis. Since CAP causes selective degeneration of primary sensory neurons of the C-fiber type and type B-cells of sensory ganglia, it is concluded that GA in CAP-sensitive primary sensory neurons represents a novel peptidergic system possibly involved in the transformation or modulation of peripheral nociceptive impulses. This system differs from the CAP-resistant GA-like neurons in other brain areas.