Early life influences, sex differences and stress vulnerability. The impact of maternal separation on adult stress sensitivity in rats

PhD ceremony: Ms. H.J. Hulshof, 14.30 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Early life influences, sex differences and stress vulnerability. The impact of maternal separation on adult stress sensitivity in rats

Promotor(s): prof. J.A. den Boer, prof. P.G.M Luiten

Faculty: Medical Sciences

Epidemiological studies reported clear differences in sensitivity for stress-related diseases between men and women. The higher prevalence of mood disorders like depression in women might be related to a higher sensitivity to stress. A higher sensitivity to stress-induced sleep disturbances and differences in stress-induced alterations of neurogenesis, the process during which new cells are produced in the brain, might contribute to the sex differences in diseases like depression. To study sex differences in stress reactivity, male and female rats were subjected to several stressors of various intensity. In general, female rats had much higher stress hormone levels than males, independent of nature and intensity of the stressor the animals were exposed to. Despite a significant stress response in both sexes and a clear sex difference in hormonal stress reactivity, the subsequent changes in sleep-wake behavior appeared rather modest and were similar in both sexes. In both sexes, stress suppressed sleep for a short-lasting period, which was followed by a compensational increase in sleep depth. Similarly, the stress-induced alterations in the production of new brain cells were comparable in male and female rats. The present findings do not support the hypothesis that sex differences in stress reactivity lead to sex differences in sleep and neurogenesis, which were suggested to play a role in the sensitivity to develop stress-related disease like depression.