Impact of different life histories on neuronal morphology in serotonin transporter deficient mice

Introduction Stress is a risk factor for developing psychiatric disorders, e.g. anxiety disorders and depression. Several hypotheses postulate that the interaction between early and later life stress is crucial for the development of psychopathology. Two currently discussed hypotheses deal with that topic: the “allostatic load” and the “mismatch” hypothesis. The former considers the accumulation of environmental adversity over the lifetime as the major risk factor. The latter postulates highest vulnerability to diseases when there is a mismatch between the individualʼs experience during early and later phases of life.

Methods Moreover, variants of serotonergic system genes interact with life events moderating the susceptibility and/or resilience for psychiatric disorders. 5-HTT knockout (KO) mice already display increased anxiety-like behavior compared to wildtype (WT) mice.

Results Bodden and coworkers (2015) showed effects of four different life histories (with matching and mismatching situations of early and later life stress) on the behavior of mice varying in 5-Htt genotype.

Using Golgi-stained sections of these mice and with the help of the Neurolucida system (MicroBrightField) we analyzed the morphology of pyramidal-like neurons in the lateral amygdala (LA) and pyramidal neurons of the infralimbic cortex (IL).

Conclusion We revealed that 5-Htt genotype as well as early and late phases of life influence neuronal morphology in the LA, and in the IL, but in different ways. Whereas in the IL alterations of gross dendritic morphology such as dendritic length and nodes were prominent, in the LA spine density changes were most evident. In general, early adverse environment resulted in higher spine densities.