Prefrontal and ventral striatal dendritic morphology: effects of life-long complex housing and amphetamine administration

Complex housing is one of the most effective experiences in producing plastic changes in the brain. For example, animals living in complex environments show widespread synaptic changes both in cerebral cortex and the striatum. Similarly, repeatedly treating animals with psychomotor stimulants such as amphetamine also induces changes in prefrontal cortex and the striatum. The purpose of the current study was to determine the effects of life-long housing in complex environments versus standard laboratory caging and this experience influenced the later effects of amphetamine. Both male and female Long-Evans rats were placed in complex environments for about 110 days, beginning at conception, until adulthood at which time they were administered saline or amphetamine daily (1 mg/kg, IP) for 14 days. A week later the brains were harvested and processed for Golgi-Cox staining to analyze dendritic length, branching, and spine density in prefrontal cortex (areas Cg3 and AID) and Nucleus Accumbens (NAcc). The results showed that the prolonged period of enriched housing produced significant synaptic changes in all three measures in all three areas measured, but the effects differed in the two sexes. Amphetamine produced large synaptic changes in Cg3 and NAcc in males but only spine changes in those regions in females. Complex housing did not interact with the later effects of amphetamine administration. Thus, both complex housing and amphetamine can produce a range of synaptic changes depending upon sex and area examined. Furthermore, the effect of complex housing varies depending on the details of when complex housing is begun and how long it lasts.