Janet E Stockard

Effect of Docosahexaenoic Acid Content of Maternal Diet on Auditory Brainstem Conduction Times in Rat Pups

Previous studies of dietary docosahexaenoic acid (DHA; 22:6n–3) effects on neurodevelopment have focused mainly on effects on the visual system; these studies may be confounded by effects on the retina rather than on neural pathways. Auditory brainstem conduction times (ABCTs) provide an alternate measure of central neural development. We conducted a dose-response study in which ABCTs were measured in pups whose dams were fed diets containing one of three levels of DHA (2, 4 or 6% of total fatty acids) from a single cell oil. Diets were fed during pregnancy and lactation, and pups were randomly cross-fostered on postnatal day 3 to minimize litter effects. ABCTs showed a dose-response effect, with higher levels of dietary DHA being associated with longer conduction times on postnatal day 31 (p < 0.05). Higher dietary DHA was reflected in pup cerebrums collected on postnatal days 3 and 31, and levels of arachidonic acid (AA, 20:4n–6) were inversely related to levels of DHA. This study demonstrated that the auditory brainstem response is sensitive for identifying effects of diet on neurodevelopment, and that supplementing the maternal diet with high levels of DHA may negatively impact development of the central auditory system of offspring.

Vibroacoustic Stimulation and Auditory Acuity in Preterm Infants

Vibroacoustic stimulation (VAS) is widely accepted as a simple and inexpensive adjunctive antenatal test for fetal well-being. However, possible adverse effects of VAS on auditory acuity are not completely known and are of concern, especially for infants delivered prematurely. The purpose of our study was to evaluate neonatal hearing with the brain stem auditory evoked response (BAER) in 33 preterm neonates exposed to acoustic stimulation in utero and to compare the results with those of 33 preterm neonates who were not exposed to acoustic stimulation. Of the 33 exposed neonates, four had abnormal BAER results, indicating an apparent hearing loss. In three of four cases, an infectious etiology was found, suggesting a lack of association between antenatal VAS and hearing loss. By comparison, of the 33 preterm infants not exposed to VAS antenatally (control group), one infant had an abnormal BAER result and was subsequently diagnosed to have suffered a congenital hearing loss.Thus, the risk of acoustic trau...

The Effect of Dietary Docosahexanoic Acid (DHA) on Cochlear Function in Developing Rat Pups

The Effect of Dietary Docosahexanoic Acid (DHA) on Cochlear Function in Developing Rat Pups

Dietary Docosahexanoic Acid (DHA) Effects upon the Rat Pup Auditory System|[bull]| 1526

Rats fed diets high in n3 fatty acids have lower whole brain levels of myelin basic protein, lower activities of 2′-3′cyclic nucleotide 3′-phosphodiesterase(an indicator of myelination) (DiBiase & Salvati, 1997), and longer auditory brainstem conduction times (ABCTs) (Saste et al., in press). We investigated the effects of varying levels of the n3 fatty acid DHA upon development of the rat pup auditory system.Methods: Dams were fed, from day 2 of gestation and throughout lactation, a purified diet whose fat source (22% of cals) was a vegetable oil blend supplemented with an algae oil containing 0% or 3% DHA. On postnatal day(pnd) 3, pups were culled to 10 per dam and were randomly cross fostered among dams of the same diet group to minimize litter effects (n=6 dams per diet group, 60 pups per diet group). Milk from culled pup stomachs was used for fatty acid analysis. On pnd 15, auditory electromyelographic reflexes (AEMR) to 130 db peak sound pressure level clicks were recorded from needle electrodes placed in the muscle of the thigh of 20 pups per diet group; pups were then sacrificed and brainstems removed for fatty acid analysis. For the remaining 40 pups per diet group, ABCTs were measured on pnd 24 and 31, and the postnatal day of appearance of the auditory startle reflex was determined. An additional group of dams fed 1% DHA diet had pups whose weight gains were 2/3 that of dams fed the 0% or 3% DHA diets; data from these pups are not presented. Results: Length of gestation, maternal weight gains and pup weights on pnd 3 did not differ between diet groups. Weight gains to pnd 12 were slightly lower among pups of dams fed the 3% DHA diet. The fatty acid composition of dam milk and pup brainstems reflected maternal diet. AEMRs were not different, however, ABCTs on pnd 24 were longer and the time of appearance of the auditory startle reflex was later in pups of dams fed 3% DHA.Conclusion: High levels of dietary DHA during development may be associated with delays in myelination of the central nervous system as suggested by longer ABCTs and a delay in appearance of the auditory startle reflex. Similar AEMRs between diet groups suggest minimal effects upon the peripheral nervous system. Table

Auditory Function in Rat Pups Exposed Perinatally to Zidovudine (ZDV)|[dagger]| 693

Prenatal and postnatal treatment of HIV-infected pregnant women and their newborns with zidovudine is routinely used to reduce transmission of the virus to the fetus/newborn. However, little is known about the effects of ZDV-treatment on the fetus. A high incidence of auditory dysfunction has been noted among children in the Pediatrics AIDS Program at USF. The purpose of this study was to determine whether differences exist in the auditory development of rat pups treated in utero and throughout infancy with ZDV as compared with untreated pups. METHODS: ZDV syrup was added to the water supply (2mg/ml)of six timed pregnant rats throughout pregnancy and lactation beginning on day three of pregnancy. A control group of six pregnant rats was provided with plain water. Intake was measured. After a normal gestation, all rats delivered within a ten hour period. On postnatal day (pnd) three, pups within the two groups were randomly cross-fostered to five dams (8 pups/dam; 40 pups/group) to control for litter effects. On pnd 21, auditory brainstem responses were recorded under light sedation and auditory brainstem conduction time (ABCTs) were measured. On pnd 28, cochlear function (sensory cell) was assessed using distortion product otoacoustic emissions (DPOAEs). Analyses of variance (ANOVA) of pup weights, ABCTs and DPOAEs and analyses of covariance (ANCOVA) with weight as the covariant were performed on the measures of auditory function. RESULTS: Weights of pups treated with ZDV were significantly lower on pnd 3, 21 and 28. ANOVA of ABCTs revealed significantly slower conduction times in the ZDV treated pups. When weight was controlled for by ANCOVA, these differences were not statistically significant. DPOAEs in the lower end of the frequency range (below 6k Hz) were significantly lower (decibels, sound pressure level) in the ZDV treated group even after controlling statistically for weight differences. CONCLUSION: These findings suggest that ZDV may have no direct effect on the development of the brainstem auditory pathway, but cochlear development in rats may be altered by perinatal exposure to ZDV. Table

AN ANIMAL MODEL FOR ASSESSMENT OF NEURODEVELOPMENT FOLLOWING NEONATAL HYPOXIC-ISCHEMIC INJURY † 1034

AN ANIMAL MODEL FOR ASSESSMENT OF NEURODEVELOPMENT FOLLOWING NEONATAL HYPOXIC-ISCHEMIC INJURY † 1034