Effects of undernutrition on development of far-field auditory brain stem responses in rat pups.

Timed-pregnancy Sprague-Dawley rats were placed on special diets on day 15 of their pregnancy. One group received a normal, 24% protein diet, and the second a deficient, 8% protein diet. After birth the litters within each group were cross-fostered, thinned to 8 pups each, and maintained on their respective diets. Beginning with postnatal day 16 the ABR (auditory brain stem response) was repeatedly recorded from the pups until day 43. Undernourished rat pup body weights were less than one-third of those of the well-nourished litters at the conclusion of testing. ABRs taken from the undernourished group were significantly delayed in early development compared with the controls, but the differences decreased with age despite continuation of a deficient diet. A second experiment was run to rule out body temperature differences between the two groups and showed that the ABR effect was not solely due to this variable. These results indicate that undernourishment is one of the factors that can affect the rate of maturation of the ABR.