Role of kynurenic acid on vestibulo-autonomic symptoms following unilateral labyrinthectomy in rats

Abstract

Unilateral labyrinthectomy produces vestibular symptoms that abate over time in a process of behavioral recovery known as vestibular compensation. To investigate the role of glutamate receptors in vestibulo-autonomic symptoms, we measured spontaneous nystagmus and c-Fos expression in the medial vestibular nucleus (MVN) and the solitary tract nucleus (STN) in unilateral labyrinthectomized Sprague-Dawley rats treated with kynurenic acid, a broad spectrum glutamate receptor antagonist, 30 min before labyrinthectomy. Spontaneous nystagmus occurred after unilateral labyrinthectomy (UL), and nystagmus decreased gradually over time. Spatial expression of c-Fos in the MVN following UL corresponded to disappearance of spontaneous nystagmus. Expression of c-Fos in the STN decreased 24 h after UL. Pretreatment with kynurenic acid decreased c-Fos expression in both the MVN and STN and decreased spontaneous nystagmus. These results suggest that pretreatment with kynurenic acid facilitates recovery of autonomic symptoms as well as behavioral response following UL.