Malnutrition during central nervous system growth and development impairs permanently the subcortical auditory pathway

The brain that grows and develops under the continued influence of malnutrition presents permanent impairment on functioning and neurotransmitter release. The aim of this study was to investigate the chronic effects of neonatal food restriction on neurochemical and neurodynamical aspects within the primary auditory sensory pathway. Our working hypothesis is that neonatal malnutrition may affect the flow of primary sensory information both at a neurochemical and neurodynamical level. To test this hypothesis, three groups of rats were assigned, from birth to 370 days of life, to the following dietary scheme: a well-nourished (WN) group fed ad libitum lab chow diet; an undernourished (UN) group fed 60% of diet consumed by WN group; and a rehabilitated group, undergoing same dietary restriction as undernourished until 42 days of age and thereafter fed ad libitum until the end of the experiment. At 370 days of age, the animals were submitted to brainstem auditory-evoked potentials (BAEPs) recordings and sacrificed for neurochemical evaluation of glutamate release. Undernutrition decreased glutamate release in the cortex, hippocampus, midbrain and brainstem, and significantly increased the latency of BAEP wave V. In addition; the re-establishment of the dietary conditions was not sufficient to reverse the neurochemical and electrophysiological alterations observed in the UN group. Taken altogether, our results suggest that malnutrition imposed at a critical development period caused an irreversible effect within the auditory primary sensory pathway.