Topical Application of Substance P Facilitates Vestibular Functional Recovery Induced by AMPA in the Guinea Pig

Hypothesis: Topical Substance P (SP) application facilitates recovery from vestibular disorders induced by (±)-α-amino-3-hydroxy-5-methyl-isoxazole-4propionic acid (AMPA) in guinea pigs and may offer a treatment strategy for patients with peripheral vestibular disorders. Methods: Sixteen Hartley white guinea pigs were assigned to groups administered with SP and artificial perilymph. A hole was drilled adjacent to a round window and AMPA was infused into the hole to induce a vestibular disorder. Thereafter, SP or artificial perilymph was delivered via an osmotic pump inserted into the hole. We observed spontaneous nystagmus and measured vestibulo-ocular reflexes (VOR) gains using sinusoidal rotation tests. Results: Spontaneous nystagmus decreased immediately after SP infusion, and the gain ratios were significantly higher than those in the control group at 3 and 7 days after treatment. Conclusion: Topical SP application facilitates recovery from AMPA-induced vestibular disorders in guinea pigs.