Samenvatting

The hippocampus is a brain structure that is part of the limbic system, which is involved in emotion and memory. In humans, major influences like war, rape, near death experience and natural disasters may lead to a psychiatric disorder called post traumatic stress disorder (PTSD). Stress is also thought to be the most important inducing factor in the onset of depression.

In this study the structural and molecular changes in the CA1 region of the hippocampus are investigated in two different animal models. The inescapable footshock (IFS) procedure was used as a model for PTSD in male Sprague-Dawley rats. The IFS consisted of 10 randomized inescapable footshocks, which leads to long lasting increased anxiety. The second model used was the olfactory bulbectomized (OBX) rat. The OBX rat models chronic depression. In the OBX rat the olfactory bulbs are surgically removed and this leads to behavior changes (hyperactivity in the openfield paradigm) that can be normalized by chronic antidepressant treatment and not by acute treatment..
The structural effects of IFS were investigated by measuring the number of branching points and spines on Golgi stained pyramidal neurons from the CA1 area of the hippocampus. The effect of OBX was investigated by measuring the expression of GABAAα2 , 5-HT-1A BDNF, and CRF mRNA with use of in situ hybridization (ISH).

IFS leaded to a decreased number of total branching points. This decrease was mainly caused by a decrease in branching points within a radius from 50 to 100 µm. The amount of spines was lower in the first 40 µm of the first branch than in the second 40 µm. Also, the results showed a higher amount of spines on the second branch than on the first. There was no significant difference of spine density between the control and the shocked group.
OBX had no significant effect on the mRNA expression of the GABAAα2 receptor. It takes 4 to 6 weeks before the autoradiograms for the other genes are black enough for analyses and therefore we have not yet the data for the other mentioned genes. However the ISH data for these genes will be presented during the final presentation.
In conclusion, the methods used for these studies are suitable for investigating the aims of our studies, but the measurements has to be extended (e.g. more animals, different brain regions and more cells analyzed per brain region) before final conclusions can be drawn.