Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6285799 | Neuroscience Letters | 2009 | 4 Pages |
Abstract
Previous studies have reported localization of substance P (SP) within the inner ear and that SP exists abundantly within vestibular endorgans. While SP's functional role in the inner ear remains unclear, SP can act as a neuromodulator in the CNS and directly influences neuronal excitability. We hypothesized that SP might influence neuronal excitability within the vestibular periphery. The present study used the sinusoidal rotation test to investigate the influence of SP after its local application in the guinea pig unilateral inner ear. A tiny hole was made adjacent to the round window in the right ears of Hartley white guinea pigs that had normal tympanic membranes and Preyer reflexes. An osmotic pump infused SP (10â4Â M, 10â3Â M, and 10â2Â M), neurokinin-1 (NK-1) receptor antagonist (10â3Â M) alone, or SP (10â3Â M)Â +Â NK-1 receptor antagonist (10â3Â M) through this hole, with rotation tests performed before, and 12Â h and 24Â h after the treatment. Results were used to calculate the vestibulo-ocular reflex (VOR) gains. After administration of 10â3Â M and 10â2Â M SP, significant increases in the VOR gains were noted at 12Â h after treatment, with these gains disappearing by 24Â h after treatment. This increase was not observed when there was simultaneous NK-1 receptor antagonist administration. There were also no changes in the VOR gains noted after administration of 10â4Â M SP or the NK-1 receptor antagonist alone. These results indicate the possibility that SP may act on vestibular endorgans as an excitatory factor via the NK-1 receptors.
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Authors
Hiroshi Orita, Hiroaki Shimogori, Hiroshi Yamashita,