Immunohistochemical evidence for enkephalin and neuropeptide Y in rat inferior colliculus neurons that provide ascending or commissural fibers.

Enkephalin- and neuropeptide Y-expressing neurons which offer commissural axons or axons toward auditory thalamus were identified in the rat inferior colliculus. These neurons exhibited a differential distribution pattern. The results provide evidence for regional specificity and chemical heterogeneity of neurons in the auditory midbrain.