Adolescent cocaine exposure simplifies orbitofrontal cortical dendritic arbors

Area of Science:

• Neuroscience
• Neurobiology
• Developmental Neuroscience

Background:

• Cocaine and amphetamine alter dendritic spines in brain regions like the orbitofrontal cortex (oPFC).
• The impact of these drugs on dendrite structure and the role of pre-existing cellular traits in vulnerability to substance abuse are not fully understood.
• Animal models allow for pre- and post-drug exposure assessment of neurobehavioral phenotypes.

Purpose of the Study:

• To investigate the long-term effects of adolescent cocaine exposure on dendrite structure in the oPFC.
• To determine if pre-existing cellular characteristics influence behavioral responses to cocaine.
• To explore the relationship between cocaine-induced structural changes and behavioral vulnerability.

Main Methods:

• Mice were exposed to cocaine during early adolescence (postnatal days 31-35).
• Excitatory neurons in the deep-layer oPFC were imaged and reconstructed.
• Dendritic arbors of orbital neurons were analyzed in both control mice and a genetic model of cocaine vulnerability (p190rhogap+/- mice).

Main Results:

• Adolescent cocaine exposure resulted in shortened and simplified dendritic arbors in the oPFC, particularly in the basal region.
• In contrast, drug-naïve p190rhogap+/- mice, which exhibit heightened cocaine sensitivity, showed intact oPFC dendritic arbors.
• This suggests cocaine-induced structural changes are more critical than baseline structural differences.

Conclusions:

• Adolescent cocaine exposure induces lasting alterations in oPFC dendrite structure.
• Cocaine-induced modifications in dendrite structure are likely key contributors to behavioral effects and vulnerability.
• Pre-existing structural abnormalities in oPFC neurons may play a lesser role in cocaine vulnerability compared to drug-induced changes.