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Corpus callosum: ovarian hormones and feminization
R H Fitch1, P E Cowell, L M Schrott
1Biobehavioral Sciences Graduate Degree Program, University of Connecticut, Storrs 06269.
Brain Research
|March 1, 1991
Summary
Female rats
Area of Science:
- Neuroscience
- Developmental Biology
- Endocrinology
Background:
- The corpus callosum in rats exhibits sexual dimorphism, with males typically having a larger structure.
- Neonatal testosterone in males and ovarian hormones in females are thought to influence this sexual dimorphism.
Purpose of the Study:
- To investigate the role of ovarian hormones in the differentiation of the female rat corpus callosum.
- To determine the sensitive period for ovarian hormone action on callosal development.
Main Methods:
- Female rats underwent ovariectomy (Ovx), testosterone propionate (TP) administration, or sham surgery on postnatal days 8, 12, or 16.
- Callosal area, perimeter, length, and widths were measured at 110 days of age.
- Width measurements were analyzed using factor analysis.
Main Results:
- Ovariectomy, regardless of the timing (days 8, 12, or 16), led to an enlarged callosal area and increased specific width factors.
- Testosterone propionate administration had no significant effect on any measured callosal variable at any tested time point.
- Control male and female rats displayed the expected sexual dimorphism in corpus callosum morphology.
Conclusions:
- Ovarian hormones feminize the female rat corpus callosum, and their removal leads to defeminization.
- The effectiveness of ovariectomy as late as day 16, contrasted with the lack of effect from TP treatment, suggests separate sensitive periods for masculinization and feminization processes.