Thyrotropin-releasing hormone- and GABA-like immunoreactivity coexist in neurons in the dorsal horn of the rat spinal cord.

In order to determine which types of neuron in spinal dorsal horn contain the peptide TRH, pre-embedding immunocytochemistry with antiserum to TRH was combined with post-embedding detection of GABA- and glycine-like immunoreactivity. The majority (88/101) of TRH-immunoreactive neurons were also GABA-immunoreactive, but none were glycine-immunoreactive. This suggests that TRH is mainly present in inhibitory interneurons which release GABA but not glycine, and provides further evidence that there are functional differences between those GABAergic neurons in the superficial dorsal horn that contain glycine, and those that do not.