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Perinatal glucocorticoids disrupt learning: a sexually dimorphic response
Insights
Perinatal exposure to synthetic glucocorticoids like dexamethasone impairs spatial learning in rats. Female rats show greater impairment, suggesting gender-specific effects on hippocampal development.
Area of Science:
- Neuroscience
- Developmental Biology
- Endocrinology
Background:
- Perinatal glucocorticoid exposure can disrupt hippocampal-dentate gyrus development by inhibiting neurogenesis.
- This disruption may lead to long-term cognitive deficits, particularly in hippocampal-dependent functions.
- Understanding these effects is crucial for identifying risks associated with early-life stress or medical treatments.
Purpose of the Study:
- To investigate the long-term effects of perinatal dexamethasone exposure on hippocampal-dependent spatial learning and motor coordination in rats.
- To determine if these effects are dose-dependent and exhibit gender differences.
Main Methods:
- Rats of both sexes received high (100 mg/kg) or low (1 mg/kg) dose dexamethasone on postnatal day four.
- Control groups received saline or nutritional deprivation.
- Behavioral tests assessing motor coordination and spatial learning/reversals were conducted in adulthood.
Main Results:
- Dexamethasone treatment impaired spatial learning and reversal acquisition in a dose-dependent manner.
- Low-dose dexamethasone impaired learning compared to controls; high-dose caused significant impairments.
- Female rats in the high-dose group showed greater learning deficits than males.
Conclusions:
- Perinatal dexamethasone exposure causes lasting deficits in hippocampal-dependent spatial learning.
- The observed impairments are dose-dependent and show significant gender differences, with females being more vulnerable.
- Enhanced glucocorticoid binding in female hippocampi may underlie these gender-specific effects.
Abstract:
Glucocorticoid hormones administered during the perinatal period transiently inhibit postnatal granule cell neurogenesis, and thus interfere with normal hippocampal-dentate gyrus development. Chronic deficits on behavioral tests sensitive to hippocampal-dentate function result from such treatments. In the present study rats of both sexes received either a high dose (100 mg/kg) or low dose (1 mg/kg) of dexamethasone (a synthetic glucocorticoid) on postnatal day four. Control subjects received saline or nutritional deprivation intended to produce body and brain growth suppression comparable to that observed in low dose subjects. Behavioral tests sensitive to cerebellar (motor coordination) and hippocampal (place response acquisition and reversals) dysfunction were conducted in adulthood. Control and nutritional control subjects did not differ from each other on any behavioral measures. Motor coordination tests revealed no evidence of chronic dysfunction in dexamethasone treated or nutritionally deprived subjects. Spatial learning and reversal tests revealed a gender and dose-response effect for dexamethasone treatment. Low dose subjects were impaired relative to controls. High dose subjects exhibited significant learning impairments relative to low dose and saline or nutritional control subjects. Within the high dose group only, female subjects were more impaired than male subjects. These gender dependent effects may be related to enhanced glucocorticoid binding in the hippocampi of female versus male rats.