Mechanisms of high-intensity sound exposure on inhibiting hippocampal long-term potentiation: role of brain-derived neurotrophic factor

Exposure to humans and experimental animals to loud noises produce cognitive and emotional disorders and recent studies have shown that hippocampal neuronal function is affected by auditory stimulation or deprivation. We have found previously that in the hippocampus of rats exposed to high-intensity sound (110 dB) for one-minute the Schaffer-CA1 long-term potentiation (LTP) is strongly inhibited. Here we investigated possible mechanisms involved in this effect. We found, using c-fos expression, that exposure to 110 dB sound-activated neurons in the CA1 and CA3 hippocampal region. Using electrophysiological recordings in hippocampal slices, we found that both GABAergic and glutamatergic neurotransmission were unaffected by high-intensity sound stimulation. However, hippocampal brain-derived neurotrophic factor (BDNF), which is involved in promoting hippocampal synaptic plasticity, presented decreased levels in sound-stimulated animals. Perfusion of slices with BDNF revert the inhibition of LTP after a single sound stimulus in comparison to sham-stimulated rats. Furthermore, the perfusion with LM 22A4, a TrkB receptor agonist also rescued LTP from sound-stimulated animals. Our results strongly suggest that the exposure to high-intensity sound inhibits the BDNF production in the hippocampus, which could be a possible mechanism of the inhibition of LTP by high-intensity sound exposure.