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Auditory brainstem evoked response in juvenile rats fed rat milk formulas with high docosahexaenoic acid
Nancy Auestad1, Janet Stockard-Sullivan, Sheila M Innis
1625 Cleveland Avenue, Ross Products Division, Abbott Laboratories, Columbus, OH 43215, USA. nancy.auestad@abbott.com
Insights
Postnatal high docosahexaenoic acid (DHA) supplementation shortened auditory brainstem-evoked response (ABR) in juvenile rats. This contrasts with prenatal DHA, suggesting timing of supplementation impacts auditory development and norepinephrine levels.
Area of Science:
- Neuroscience
- Nutritional Science
- Developmental Biology
Background:
- Previous research linked prenatal docosahexaenoic acid (DHA) to longer auditory brainstem-evoked response (ABR) in juvenile rats.
- High DHA diets were associated with altered brain fatty acid profiles, specifically higher DHA and lower arachidonic acid (ARA).
Purpose of the Study:
- To investigate the effects of postnatal DHA supplementation on auditory brainstem-evoked response (ABR) in juvenile rats.
- To examine the impact of DHA and ARA levels on brain fatty acid and norepinephrine concentrations following postnatal diet interventions.
Main Methods:
- Rat pups received milk formulas with varying DHA and ARA levels until postnatal day 19, followed by corresponding diets.
- Auditory brainstem-evoked response (ABR), brain fatty acid composition, and monoamine levels were assessed on postnatal days 26-28.
- Statistical analysis was performed using ANOVA.
Main Results:
- Postnatal DHA and ARA supplementation increased their respective levels in the brain.
- A shorter ABR was observed in the high-DHA group compared to the DHA + ARA group.
- Norepinephrine levels in the inferior colliculus were lower in the high-DHA group than the DHA + ARA group.
Conclusions:
- Postnatal high-DHA diets resulted in shorter ABR compared to diets supplemented with both DHA and ARA, contrasting with findings from prenatal DHA exposure.
- Dietary DHA supplementation influences norepinephrine levels in the auditory pathway.
- Further research is required to elucidate the precise relationship between DHA intake timing, norepinephrine, and auditory system development.
Unlabelled:
Previous studies found that juvenile offspring of rats fed high docosahexaenoic acid (DHA; 22:6n-3) diets through gestation and lactation had longer auditory brainstem-evoked response (ABR) accompanied by higher 22:6n-3 and lower arachidonic acid (ARA; 20:4n-6) in brain. In the present study, ABR was assessed in juvenile rats fed high-DHA diets only postnatally.
Methods:
Rat pups were fed rat milk formulas with varying amounts of DHA and ARA to 19 days of age followed by diets with the corresponding fatty acids. The high-DHA group was fed 2.3% of fatty acids as DHA, the DHA + ARA group was fed DHA and ARA at 0.6 and 0.4% of fatty acids, levels similar to those in some infant formulas, and the unsupplemented group was fed no DHA or ARA. ABR and fatty acid and monoamine levels in brain were measured on postnatal days 26-28. Statistical analyses were measured by ANOVA.
Results:
ARA and DHA levels in brain increased with supplementation. ABR was shorter in the high-DHA group than the DHA + ARA group and not different from the unsupplemented or dam-reared suckling group. Norepinephrine levels in the inferior colliculus were lower in the high-DHA group than the DHA + ARA group and higher in all formula groups compared to the dam-reared group.
Conclusion:
In contrast to the longer ABR in juvenile offspring of rats fed high-DHA through gestation and lactation, ABR was shorter in juvenile rats fed high-DHA diets only after birth than rats fed ARA + DHA. Further studies are needed to understand the relationship between dietary DHA, norepinephrine, and auditory system development over a range of DHA intakes and discrete periods of development.
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