Chronic Noise Exposure Induces Anxiety-Like Behavior and Enhances the Excitability of Dorsal Raphe Serotonergic Neurons in Mice.

This study demonstrates that chronic noise exposure induces anxiety-like behaviors in mice, as consistently observed across three classical behavioral paradigms. Electrophysiological recordings showed that chronic noise exposure is associated with increased intrinsic excitability of serotonergic (5-HT) neurons in the dorsal raphe nucleus (DRN), characterized by a depolarized resting membrane potential, increased spontaneous firing frequency, reduced rheobase, and elevated input resistance. In addition, chronic noise exposure was associated with enhanced excitatory synaptic input onto DRN 5-HTergic neurons, as reflected by an increase in the frequency, but not the amplitude, of both spontaneous and miniature excitatory postsynaptic currents. In contrast, neither intrinsic excitability nor excitatory synaptic transmission of local DRN GABAergic neurons was significantly altered. Furthermore, pharmacological blockade of AMPA and NMDA receptors indicated that the increased excitability of DRN 5-HTergic neurons cannot be fully explained by enhanced excitatory synaptic input alone, suggesting a potential contribution of intrinsic membrane mechanisms. Together, these findings provide correlational evidence that chronic noise exposure is associated with functional alterations in DRN 5-HTergic neurons and may represent a potential neural correlate of noise-related anxiety-like behavior.