Journal of chemical neuroanatomy
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J. Chem. Neuroanat. · May 2009
Expression of mu- and delta-opioid receptors in song control regions of adult male zebra finches (Taenopygia guttata).
The opioid system is known to play a role in various aspects of learning and memory in diverse species of mammals and birds. Earlier studies have localized the endogenous opioids, met- and leu-enkephalin, in the song control regions of male zebra finches (Taenopygia guttata), a sexually dimorphic species of songbirds wherein only males sing. Recent research has shown that levels of enkephalin increase in some of the song control regions during singing and that blocking opioid receptors with the antagonist naloxone decreases the frequency of singing in songbirds. ⋯ However, HVC and RA neurons expressed marginally higher levels of mu-OR mRNA compared to the posterior nidopallium, which was confirmed by immunohistochemical localization. We also found that the dorsolateral subdivision of DLM (dorsolateral nucleus of the medial thalamus) demonstrated high levels of mu-OR immunoreactivity. Our results suggest that the ORs may be involved in modulating different aspects of vocalization and/or gating auditory input, as well as motor control.