Refinement of Nucleus Accumbens Neuronal Dynamics During Cocaine Self-Administration Training

Area of Science:

• Neuroscience
• Addiction Research
• Behavioral Science

Background:

• Drug addiction involves distinct phases, from acquisition to maintenance.
• The nucleus accumbens (NAc) is crucial for cocaine self-administration and seeking behaviors.
• Neuronal activity shifts in the NAc during addiction progression remain unclear.

Purpose of the Study:

• To investigate how nucleus accumbens (NAc) principal medium spiny neuron (MSN) activity patterns change during cocaine self-administration.
• To understand the neuronal dynamics underlying the transition from cocaine acquisition to maintenance.

Main Methods:

• In vivo calcium imaging (GCaMP6m) was used to monitor NAc MSN activity in mice over 11 days of cocaine self-administration.
• Behavioral analysis tracked operant responding and locomotion.
• Neuron-tracking techniques were employed to analyze ensemble dynamics.

Main Results:

• Mice showed stabilized operant responding and locomotion over 11 days.
• A subset of NAc neurons increased activity contingent to lever pressing for cocaine.
• This contingent neuronal activity expanded in the initial days and then refined, suggesting "expansion-refinement dynamics" corresponding to addiction phases.
• The composition of the active NAc ensemble dynamically changed throughout training.

Conclusions:

• The observed "expansion-refinement dynamics" and compositional changes in NAc neuronal ensembles may underlie the transition from cocaine acquisition to maintenance.
• These findings highlight the dynamic circuit mechanisms within the NAc during the development of drug addiction.