Endogenous opioids facilitate intrinsically-rewarded birdsong

Area of Science:

• Neuroscience
• Animal Behavior
• Behavioral Endocrinology

Background:

• Songbirds sing in non-reproductive, gregarious contexts for song maintenance and learning.
• This singing lacks immediate social consequences but correlates with intrinsic reward and opioid markers in the medial preoptic nucleus (mPOA).

Purpose of the Study:

• To investigate the causal role of opioids, specifically mu opioid receptors (MORs), in facilitating gregarious song in European starlings.
• To determine if MORs in the mPOA influence the association between affective state and singing behavior.

Main Methods:

• Administered the MOR agonist fentanyl to male and female European starlings to assess effects on song and anxiety.
• Infused siRNA targeting MORs into the mPOA to suppress receptor expression.
• Utilized conditioned place preference (CPP) tests to evaluate song-associated reward and affective state.

Main Results:

• Fentanyl dose-dependently increased gregarious song and reduced stress/anxiety-related behaviors.
• MOR suppression in the mPOA significantly reduced gregarious song.
• MOR suppression in the mPOA disrupted the positive association between affective state and singing behavior in CPP tests.

Conclusions:

• Endogenous opioids, acting via MORs in the mPOA, are causally involved in facilitating gregarious song.
• Opioids likely facilitate singing by modulating the intrinsic reward state associated with this behavior.