Interferon α2b As a Modulator of the Afferent Glutamatergic Synapse of the Frog Vestibular Apparatus

It is known that the molecules of innate and adaptive immunity can influence the synaptic activity of the central nervous system (CNS). Interferons (IFNs) are commonly used to treat viral and oncological diseases, although they are classified as ototoxic substances and their impact on the synaptic activity of the inner ear is not yet fully understood. In this study, the effect of interferon α2b (IFN-α2b) on the function of afferent glutamatergic synapse in the presence of drug application to the synaptic zone has been analyzed. The study was performed on the isolated vestibular apparatus of a frog (Rana temporaria) using the multiunit recording. Results showed that IFN-α2b (0.2–40 ng/mL) caused an increase in the background pulse activity of afferent fibers, followed by a decrease in the frequency of discharges, especially at high concentrations of IFN-α2b. Additionally, IFN-α2b reduced the glutamate (L-Glu) evoked response and influenced the level of afferent fiber activity restored by L-Glu when the glutamate release from hair cells was blocked in hyper-Mg²⁺ and hypo-Ca²⁺ solution. This indicates that IFN-α2b has a postsynaptic effect. Overall, the findings suggest that IFN has a neuromodulating effect on the synaptic activity of the afferent synapse of the vestibular apparatus.