Differential effects of nicotine and complex housing on subsequent experience-dependent structural plasticity in the nucleus accumbens.

Drugs and other forms of experience (e.g., complex housing) share the ability to alter the dendritic fields of cortical and subcortical neurons. Although such modifications are typically considered advantageous, recent research has demonstrated that psychomotor stimulants (cocaine and amphetamine) block subsequent experience-dependent structural plasticity in the nucleus accumbens (NAcc) and parietal neocortex. The authors investigated whether these findings generalize to another commonly used stimulant (nicotine) and further asked whether prior experience blocks subsequent nicotine-related structural plasticity. Rats were given daily injections of nicotine (or saline) for 14 days either before (Experiment 1) or after (Experiment 2) 2.5-3.0 months of complex (or standard) housing. Nicotine blocked housing-related increases in dendritic branching, length, spine density, and total spines in NAcc; however, complex housing did not block the effects of nicotine. The findings indicate that there are important differences in the capacity of drugs and experience to influence subsequent modifications in dendritic structure.