Elsevier

Neuroscience

Volume 134, Issue 2, 2005, Pages 387-395
Neuroscience

Cellular neuroscience
Effects of repeated maternal stress on FOS expression in the hypothalamic paraventricular nucleus of fetal rats

https://doi.org/10.1016/j.neuroscience.2005.04.023Get rights and content

Abstract

The effects of repeated prenatal stress with different severity (restraint and immobilization) on Fos expression in the maternal and fetal hypothalamic paraventricular nucleus (PVN) were examined in rats. Acute stress treatment was performed for 30 min on gestational day 21, and repeated stress treatment for 30 min daily for 5 days from gestational days 17–21. In the parvocellular region of the maternal PVN, the stress-induced increases in the number of Fos-immunoreactive neurons were smaller in the repeated stress groups than the acute stress groups, indicating an adaptation of Fos expression to repeated stress. The attenuated Fos expression observed in the maternal PVN following repeated mild stress did not occur in the fetal PVN. In contrast, repeated immobilization stress caused a much smaller increase in Fos expression in the fetal PVN than did acute immobilization stress. The reduced Fos expression in the fetal PVN following repeated severe stress was thought to be due to cell death, since the fetal PVN in the chronic immobilization group revealed a reduction in the total number of cells and an increase in the number of apoptotic cells. In the female but not male fetuses, repeated restraint stress induced a significant increase in the number of apoptotic cells in the PVN.

These findings suggest that the fetal PVN shows no adaptation of Fos expression to repeated maternal stress, but great vulnerability to cell death, including apoptosis. In addition, stress-induced apoptosis may more easily occur in the fetal PVN in females than males.

Section snippets

Animals

Sprague–Dawley rats (Clea Japan, Tokyo, Japan) were housed at 22°C with free access to food and water, with a 12-h light/dark cycle (lights on at 8 a.m., off at 8 p.m.). Virgin female rats (8–10 weeks old) were kept with adult male rats in the same cage overnight for mating, and vaginal smears were examined the following morning. Embryonic day 0 was established as the day on which the smear was sperm-positive. Then each pregnant rat was housed separately in a plastic home cage (40×25×20cm) with

Effects of maternal stress on fetal body weights

The effects of maternal stress on fetal body weights (Table 1) revealed significant differences in the effect of sex [F(1,382)=29.04, P<0.01], stress treatment [F(1,382)=13.19, P<0.01], and stress period [F(2,382)=10.64, P<0.01]. Because there was no significant interaction between sex, stress treatment and stress period, the data from the male and female experiments were analyzed separately for each stress group. In male fetuses, the weights of the chronic immobilization (CI) group were

Discussion

The present experiments examined the effects of repeated prenatal stress with different severity (restraint and immobilization) on Fos expression in the maternal and fetal PVN. The changes in Fos expression caused by repeated stress and by acute stress were compared. Acute stress treatment was performed for 30 min on gestational day 21, and chronic stress treatment for 30 min daily for 5 days from gestational days 17–21. The following is a summary of this study: 1) In the parvocellular region

Conclusions

The fetal PVN shows no adaptation of Fos expression to repeated maternal stress, but great vulnerability to cell death, including apoptosis. Moreover, females may have greater vulnerability to stress-induced apoptosis than males.

Acknowledgments

The authors thank Dr. M. Iwamoto for advice on statistical analysis, Ms J. Ueda and K. Tanaka for technical assistance and Dr. R. C. Lee for improving the English.

References (28)

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