Expression patterns of atrial natriuretic peptide and its receptors within the cochlear spiral ganglion of the postnatal rat.

The spiral ganglion, which is primarily composed of spiral ganglion neurons and satellite glial cells, transmits auditory information from sensory hair cells to the central nervous system. Atrial natriuretic peptide (ANP), acting through specific receptors, is a regulatory peptide required for a variety of cardiac, neuronal and glial functions. Although previous studies have provided direct evidence for the presence of ANP and its functional receptors (NPR-A and NPR-C) in the inner ear, their presence within the cochlear spiral ganglion and their regulatory roles during auditory neurotransmission and development is not known. Here we investigated the expression patterns and levels of ANP and its receptors within the cochlear spiral ganglion of the postnatal rat using immunofluorescence and immunoelectron microscopy techniques, reverse transcription-polymerase chain reaction and Western blot analysis. We have demonstrated that ANP and its receptors colocalize in both subtypes of spiral ganglion neurons and in perineuronal satellite glial cells. Furthermore, we have analyzed differential expression levels associated with both mRNA and protein of ANP and its receptors within the rat spiral ganglion during postnatal development. Collectively, our research provides direct evidence for the presence and synthesis of ANP and its receptors in both neuronal and non-neuronal cells within the cochlear spiral ganglion, suggesting possible roles for ANP in modulating neuronal and glial functions, as well as neuron-satellite glial cell communication, within the spiral ganglion during auditory neurotransmission and development.