Enkephalin-like immunoreactivity in vocal control regions of the zebra finch brain.

Singing in passerine birds is an androgen-dependent behavior typical of males, and in many species is learned during an early critical period. Brain regions which control song form a rather discrete, interconnected series of nuclei which have been described in the canary and zebra finch. These regions include the caudal nucleus of the hyperstriatum ventrale (HVc), the robust nucleus of the archistriatum (RA), the magnocellular nucleus of the neostriatum (MAN), area X of the lobus parolfactorius, nucleus interface (NIF), intercollicular nucleus (ICo), and the tracheosyringeal portion of the hypoglossal motor nucleus (nXIIts). In the present report, we describe cell bodies and terminals in these brain regions which contain enkephalin-like immunoreactivity (ELI). This study is the third in a series investigating the histochemical characteristics of the vocal control system in zebra finches.