Malnutrition and environmental stimulation in rats: interpeak intervals of the brainstem auditory evoked potentials

The aim of this study was to investigate the effects of malnutrition, nutritional recovery, environmental stimulation and click intensity on the interpeak intervals of the waves of the Brainstem Auditory Evoked Potentials (BAEPs). The animals were divided into Well-nourished (W) and Malnourished (M) groups. At weaning, half of the M rats were submitted to nutritional recovery (R) until the test day. These groups were further subdivided into Stimulated (S) and Non-stimulated (N) rats. The BAEPs interpeak intervals I-III, I-IV and III-IV were analysed in independent groups of rats on the 18th, 22nd, 32nd and 42nd days of age. During the lactation period, stimulated rats presented shorter I-III, I-IV and III-IV interpeak intervals than Non-stimulated animals. This analysis also indicated a diet x stimulation x age interaction during the lactation period. The WN and MN groups showed a longer I-IV interval than the WS and MS groups, respectively, on the 18th and 22nd day of age, and the MN group also presented a longer I-IV interpeak interval than the WN group on the 22nd day of age. During the post-lactation period, stimulated animals showed shorter I-III and I-IV intervals than non-stimulated rats. Post hoc analysis indicated longer I-III and I-IV interpeak intervals in the MN than in the WN, RN and MS groups. Additionally, malnourished animals showed longer I-III and I-IV intervals than well-nourished and recovered rats when exposed to clicks of 90, 80 or 70 dB intensity. Malnutrition resulted in a delay of normal development of the brainstem auditory pathway indicated by the increases in the interpeak intervals of BAEPs waves, and environmental stimulation reduced these intervals, promoting faster nervous impulse transmission.