drop after 120 h (Osterndorff-Kahanek et al., 2015, 2018). Those experiments provided evidence for overrepresentation of genes characteristic of astrocytes and microglia in the amygdala and to a lesser extent in the nucleus accumbens at the early times, but no evidence of overexpression of genes characteristic of neurons. In the pre-frontal cortex, in contrast, neuronal genes were overrepresented along with astrocytes and, to a lesser degree, microglia (Osterndorff-Kahanek et al., 2015). A similar experiment looked only at 0 and 8 h after CIE exposure, and found many differences in gene expression in pre-frontal cortex but few in hippocampus or nucleus accumbens; the number of differentially expressed genes in pre-frontal cortex dropped markedly by 8 h (Melendez et al., 2012). Another experiment showed that pre-frontal cortex had the most differences at time 0, dropping by half at 8 h and to about 10% by 72 h (Smith et al., 2016). These experiments reveal much complexity in the timecourse and nature of genes affected, and differences among brain regions. They also suggest changes in the cellular composition of different regions at different times. Our study of a single cell type removes these complexities and focuses on understanding how a single cell type
