Preadolescent drd1-EGFP mice exhibit cocaine-induced behavioral sensitization

Area of Science:

• Neuroscience
• Pharmacology
• Developmental Biology

Background:

• Cocaine-induced behavioral sensitization is well-characterized in adult mice.
• The role of the D1 dopamine receptor in cocaine effects is established in adults.
• Effects of cocaine on D1 receptor expression and function in preadolescent animals remain less understood.

Purpose of the Study:

• To characterize cocaine-induced locomotor sensitization in preadolescent drd1-enhanced green fluorescent protein (drd1-EGFP) reporter mice.
• To compare sensitization between preadolescent drd1-EGFP and C57BL/6 mice.
• To investigate the persistence of cocaine-induced changes in preadolescent drd1-EGFP mice.

Main Methods:

• Administration of 15mg/kg cocaine three times daily for seven days to preadolescent mice (postnatal day 23).
• Assessment of horizontal locomotor activity to measure behavioral sensitization.
• Measurement of dopamine receptor mRNA levels (D1 and D2) in the caudate nucleus.
• Evaluation of sensitization retention after a two-week cocaine-free period.

Main Results:

• Both drd1-EGFP and C57BL/6 mice exhibited cocaine-induced locomotor sensitization.
• Sensitization duration was longer in preadolescent drd1-EGFP mice by day 7.
• Preadolescent drd1-EGFP mice showed elevated basal locomotor activity and higher D1/D2 dopamine receptor mRNA levels.
• Cocaine-induced sensitization was not retained after two weeks of withdrawal in drd1-EGFP mice.

Conclusions:

• Preadolescent drd1-EGFP mice serve as a viable model for studying cocaine effects.
• Cocaine-induced locomotor sensitization in preadolescent mice is transient.
• Dopamine receptor expression and function in preadolescent mice may differ from adults.