in dendritic arborization of prefrontal cortex neurons (56). The implication here is that influence of 5-HTT variation may not be limited to effects on 5-HT availability or even on the 5-HT system. Recently, this implication was confirmed in a rhesus macaque model (88), in which the rh5-HTTLPR S allele affected behavior and brain morphology but not 5-HTT (99) or 5-HT1A concentrations in vivo. Similar complexities in the likely molecular consequences of the 5-HTTLPR have been documented in humans (100–105). Collectively, mouse and monkey and human findings suggest that 5-HTTLPR’s behavioral effects on stress-reactivity may be most consistently rooted in neural development.
