Elsevier

Neuroscience

Volume 81, Issue 3, 26 September 1997, Pages 689-697
Neuroscience

Sex differences in dendritic atrophy of CA3 pyramidal neurons in response to chronic restraint stress

https://doi.org/10.1016/S0306-4522(97)00233-9Get rights and content

Abstract

The present study investigated the effects of 21 days of chronic restraint stress on neural and endocrine parameters in male and female rats. Consistent with previous results, repeated restraint stress induced apical dendritic atrophy (a decrease in the number of apical branch points and dendritic length) of the CA3c pyramidal neurons in male rats. In contrast, female rats did not show significant dendritic atrophy in the apical field in response to repeated restraint stress. Female rats did show a decrease in the number of branch points in the basal dendritic tree compared to male rats in response to repeated restraint stress. Baseline and stress levels of plasma corticosterone were higher in female rats compared to male rats. Females exhibited slightly longer increases in corticosterone levels throughout the 21 days of restraint stress than males, indicating that the male corticosterone response to stress exhibited greater habituation. Plasma corticosteroid-binding globulin levels of female rats were also higher than those of male rats throughout the experiment. There was no change in plasma corticosteroid-binding globulin levels in male rats during the restraint stress, while there was a decrease in plasma corticosteroid-binding globulin levels in female rats during the restraint stress. Plasma estradiol levels in female rats also decreased in response to the chronic stress.

In view of the qualitatively different dendritic atrophy found in males and females it appears unlikely that sex differences in the corticosteroid-binding globulin and corticosterone response can account for these morphological differences.

Section snippets

Animals

Sixteen female (50–56 days old) and 16 male (45–49 days old) 200 g Sprague–Dawley rats were purchased from Charles River. Animals were housed in same-sex pairs in wire-mesh hanging cages. Rats were given Purina rat chow and tap water ad libitum and maintained under a 12 h:12 h light/dark cycle (lights on at 7.00 a.m.). All animals were kept under these conditions for three weeks prior to the start of the experiment. Four days prior to the start of the restraint procedure, group mean weight for

In contrast to females, males showed dendritic atrophy in the apical tree in response to restraint stress

There were sex differences in the effects of repeated restraint stress on dendritic length, with males showing a decrease in the number and length of apical dendrites. Table 1 shows the number of branch points and dendritic length of control and stressed groups of male and female rats in both the apical and basal dendritic trees. Fig. 1 represents camera lucida drawings of a representative cell for each of the four groups of rats. Specifically, there was an interaction effect of condition by

Discussion

Consistent with previous results, male rats that underwent 21 days of restraint stress showed significant apical dendritic atrophy (a decrease in number of branch points and dendritic length) compared to non-stressed controls.21, 30Chronically restrained female rats, however, did not exhibit the severity of apical dendritic atrophy that was seen in stressed males. This result is consistent with a study in vervet monkeys, in which stressed males showed evidence of hippocampal pyramidal neuron

Conclusions

In addition to presenting the first comparison of morphological changes in the male and female rat hippocampus after repeated stress, this study also presents the first comparison of plasma corticosterone and CBG levels in male and female rats exposed to repeated stress. Females had higher basal and stress levels of both plasma corticosterone and CBG than males. They also had a more prolonged increase in plasma corticosterone levels in response to stress than males. Moreover, whereas plasma CBG

Acknowledgements

We thank Maryse Aubourg and Heather Cameron for their technical assistance. This research was supported by a NS07080 grant to BSM, and a postdoctoral fellowship from the Natural Sciences and Engineering Research Council of Canada to LAMG.

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