Conditioned dopamine release: dependence upon N-methyl-D-aspartate receptors

Area of Science:

• Neuroscience
• Behavioral Pharmacology
• Dopamine Signaling

Background:

• Contextual cues can elicit conditioned emotional responses.
• Dopamine release in the nucleus accumbens is crucial for reward and motivation.
• Understanding the neurochemical basis of conditioned responses is vital.

Purpose of the Study:

• To investigate the effect of conditioned emotional response on dopamine release in the rat nucleus accumbens.
• To examine the role of N-methyl-D-aspartate (NMDA) receptors in mediating this dopamine release.

Main Methods:

• In vivo microdialysis was used to measure extracellular dopamine levels in the rat nucleus accumbens.
• Rats were exposed to a contextual cue previously paired with footshock to elicit a conditioned emotional response.
• The NMDA antagonist dizocilpine maleate was administered into the nucleus accumbens.

Main Results:

• A conditioned emotional response significantly increased extracellular dopamine in the nucleus accumbens for up to 80 minutes.
• Dizocilpine maleate blocked the later phase of this dopamine increase but not the immediate response.
• The alpha-amino-3-hydroxy-5-methyl-4-isoxazoleproprionate/kainate antagonist did not affect dopamine release.

Conclusions:

• Acquisition of a conditioned emotional response induces lasting changes in glutamatergic control of dopamine release.
• NMDA receptor activation in the nucleus accumbens regulates the delayed phase of conditioned dopamine release.
• Glutamate inputs play a key role in the expression of conditioned emotional responses via NMDA receptors.