Neuropeptide Y in Rat Spiral Ganglion Neurons and Inner Hair Cells of Organ of Corti and Effects of a Nontraumatic Acoustic Stimulation

Abstract

Neuropeptide Y (NPY) is an important neuromodulator found in central and peripheral neurons. NPY was investigated in the peripheral auditory pathway of conventional housed rats and after nontraumatic sound stimulation in order to localize the molecule and also to describe its response to sound stimulus. Rats from the stimulation experiment were housed in monitored sound-proofed rooms. Stimulated animals received sound stimuli (pure tone bursts of 8 kHz, 50 ms duration presented at a rate of 2 per second) at an intensity of 80 dB sound pressure level for 1 hr per day during 7 days. After euthanizing, rat cochleae were processed for one-color immunohistochemistry. The NPY immunoreactivity was detected in inner hair cells (IHC) and also in pillar and Deiters' cells of organ of Corti, and in the spiral ganglion putative type I (> or = 1,009 microm(3)) and type II (< or = 225 microm(3)) neurons. Outer hair cells (OHC) showed light immunoreaction product. Quantitative microdensitometry showed strong and moderate immunoreactions in IHC and spiral ganglion neurons, respectively, without differences among cochlear turns. One week of acoustic stimulation was not able to induce changes in the NPY immunoreactivity intensity in the IHC of cochlea. However, stimulated rats showed an overall increase in the number of putative type I and type II NPY immunoreactive spiral ganglion neurons with strong, moderate, and weak immunolabeling. Localization and responses of NPY to acoustic stimulus suggest an involvement of the neuropeptide in the neuromodulation of afferent transmission in the rat peripheral auditory pathway.

Characterization of Lgr5+ progenitor cell transcriptomes in the apical and basal turns of the mouse cochlea

“…We found that the majority of the top 200 richly expressed genes in ALPs and BLPs are similar, but two genes were significantly highly expressed in ALPs, and six genes were significantly highly expressed in BLPs. Among all the genes, only NPY, which is highly expressed in BLPs, was previously reported to participate in neuromodulation of afferent transmission in the inner ear [39]. …”

Existence of Manserin, a Secretogranin II–Derived Neuropeptide, in the Rat Inner Ear

“…The following reports on the localization of neuropeptides and their physiological roles in the inner ear: neuropeptide Y in the organ of Corti and spiral ganglion (Gomide et al 2009); pituitary adenylate cyclase-activating polypeptide in the organ of Corti and spiral ganglion (Drescher et al 2006); neurotensin in the inner hair cells, Deiters cells, and spiral ganglion (Gomide et al 2005); and substance P, enkephalin, and calcitonin gene-related peptide in the organ of Corti (Ylikoski et al 1989). Furthermore, it has been reported that dynorphin, calcitonin gene-related peptide, and enkephalin are distributed in the efferent fibers of the lateral olivocochlear nucleus and are involved in the synaptic transmission of type I spiral ganglion cells that form a synapse with the inner hair cells (Raphael and Altschuler 2003).…”