The size of the splenium of the rat corpus callosum: Influence of hormones, sex ratio, and neonatal cryoanesthesia

Nuñez, Joseph L.; Juraska, Janice M.

doi:10.1002/(sici)1098-2302(199812)33:4<295::aid-dev1>3.0.co;2-l

Cited by 23 publications

(13 citation statements)

References 35 publications

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“…Consistent with previous work in our laboratory, we found a sex difference in size and myelination in the splenium (Kim, Ellman, & Juraska, 1996;Nunez & Juraska, 1998). We also found similar sex differences in size and myelination in the genu.…”

Section: Discussionsupporting

confidence: 92%

“…Sex differences have also been found in the size of the rat corpus callosum, including the splenium (posterior 20% of the corpus callosum) (Nunez & Juraska, 1998), with males having a larger callosal area compared to females (Berrebi et al, 1988;Bimonte, Fitch, & Denenberg, 2000;Fitch et al, 1991). Differences in callosal area reflect differences in the underlying axonal composition of the corpus callosum.…”

Section: Introductionmentioning

confidence: 98%

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Increases in size and myelination of the rat corpus callosum during adulthood are maintained into old age

Yates

Juraska

2007

Brain Research

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Although there are indications of growth in the size and myelination of the rat corpus callosum during adulthood, it is not known how long this growth continues. In addition, the potential for age-related changes in these measures to affect the sex differences seen in adulthood has not been examined. Here the size of callosal subregions and area occupied by myelin were examined in the genu and splenium of male and female rats in adulthood, middle-age, and old age. Our findings revealed increases both in size and in the area composed of myelin between adulthood and middle-age that were maintained into old age, with no indications of age-related loss in either the genu or splenium of the rat.

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Section: Discussionsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 98%

Increases in size and myelination of the rat corpus callosum during adulthood are maintained into old age

Yates

Juraska

2007

Brain Research

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“…Testosterone injections in females increase the size of their splenium. In accordance with the author's hypothesis, Nunez & Juraska (1998) found that the offspring sex ratio of females correlates with their splenial area.…”

Section: Splenial Area Of Ratssupporting

confidence: 91%

Evidence that mammalian sex ratios at birth are partially controlled by parental hormone levels around the time of conception

James

2007

Journal of Endocrinology

141

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“…The splenium, defined as the posterior 20% of the total callosal length, carries axons from the visual cortex (Kim et al, 1996). Sex differences in the size of the splenium (Nunez and Juraska, 1998) are due to a greater number of myelinated axons within the splenium of males though there are no differences in total axon number (Kim et al, 1996). Differences in myelinated axon number are established by young adulthood (day 60), but are not seen in prepubertal animals examined at 25 days of age (Kim and Juraska, 1997).…”

Section: Introductionmentioning

confidence: 99%

Pubertal ovarian hormone exposure reduces the number of myelinated axons in the splenium of the rat corpus callosum

Yates

Juraska

2008

Experimental Neurology

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The size of the female rat corpus callosum decreases in response to pubertal ovarian hormone exposure, but the underlying changes in axonal composition have not been examined. In the current study, animals underwent ovariectomy or sham surgery at day 20, and the number of myelinated and unmyelinated axons were examined in young adulthood (2 mo.) using electron microscopy. Ovariectomized animals had a greater number of myelinated axons compared to intact animals, while total axon number was not affected. Ovarian hormone exposure seems to limit the number of axons that become myelinated in the splenium, while not affecting the number of axons crossing through the region. Keywordsestrogen; progesterone; myelin; oligdodendrocyte; adolescence; corticosteroids The corpus callosum is sexually dimorphic in the rat, with males having a larger total corpus callosum size than females (Berrebi et al, 1988;Fitch et al, 1991;Bimonte et al., 2000a;2000b;2000c;Denenberg et al., 1991). The splenium, defined as the posterior 20% of the total callosal length, carries axons from the visual cortex (Kim et al., 1996). Sex differences in the size of the splenium (Nunez and Juraska, 1998) are due to a greater number of myelinated axons within the splenium of males though there are no differences in total axon number (Kim et al., 1996). Differences in myelinated axon number are established by young adulthood (day 60), but are not seen in prepubertal animals examined at 25 days of age (Kim and Juraska, 1997). On the other hand, females have more total axons at day 25. However, because of continued axon elimination in females this difference is abolished by day 60 (Kim and Juraska, 1997). Thus, the onset of puberty around day 35 may affect both myelination and axon withdrawal.Prepubertal ovariectomy (OVX) at day 25 has been shown to increase the overall size of the corpus callosum in adulthood (Bimonte et al., 2000a(Bimonte et al., , 2000b(Bimonte et al., , 2000c, while OVX at day 70 is without effect (Bimonte et al, 2000c). The underlying structural changes responsible for this increase in size have not been examined. It is possible that the removal of ovarian hormones before puberty reduces axon elimination or increases the number of axons that get myelinated, resulting in a greater callosal size. In the primary visual cortex, which projects axons through Corresponding author: Janice M. Juraska, Ph.D., Department of Psychology, 603 E. Daniel St., Champaign, IL 61820, (217) 333-8546, Fax: (217) 244-5876, jjuraska@cyrus.psych.uiuc.edu. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Pu...

show abstract

The size of the splenium of the rat corpus callosum: Influence of hormones, sex ratio, and neonatal cryoanesthesia

Cited by 23 publications

References 35 publications

Increases in size and myelination of the rat corpus callosum during adulthood are maintained into old age

Increases in size and myelination of the rat corpus callosum during adulthood are maintained into old age

Evidence that mammalian sex ratios at birth are partially controlled by parental hormone levels around the time of conception

Pubertal ovarian hormone exposure reduces the number of myelinated axons in the splenium of the rat corpus callosum

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