Primary afferent excitatory transmission recorded intracellularly in vitro from rat medial vestibular neurons

Abstract

Intracellular recordings were made from rat medial vestibular nucleus (MVN) neurons in transverse brain slices containing the root of the vestibular nerve (N. VIII). Electrical stimuli applied to the N. VIII tract evoked an orthodromic excitatory postsynaptic potential (EPSP) that lasted about 50 ms following a 0.5 to 1.5 ms delay between the stimulus artifact and synaptic potential. These orthodromic EPSPs were insensitive to the following antagonists: atropine, hexamethonium, diphenhydramine, and caffeine. Based on these results we conclude that the primary afferent excitatory transmitter is not acetylcholine, histamine, or adenosine, respectively. However, kynurenic acid, a general excitatory amino acid receptor antagonist, blocked the orthodromic EPSP while having no effect on the resting membrane potential, input resistance, or action potential configuration of MVN neurons. Our data suggest that an excitatory amino acid, or amino acid-like substance, is responsible for primary afferent excitatory transmission in the rat medial vestibular nucleus.

Localization of vesicular glutamate transporters in the peripheral vestibular system of rat

“…Previous physiological and morphological data indicated that VG neurons could be activated by the excitatory transmitter of the hair cells at the peripheral afferent nerve endings, and could release glutamate to excite the central otolith neurons in the brain [4][5][6] . Up to date, VGluTs have received wide investigations in various brain regions, spinal cord, and peripheral structures such as dorsal root ganglion, trigeminal ganglion, cochlea, and retina [7][8][9][10][11][12] .…”

Toward Maturation of the Vestibular System: Neural Circuits and Neuronal Properties

“…dopamine and serotonin) and neuroactive peptides [73] . Given that glutamatergic transmis-165 sion is the major excitatory input at the projection fields of vestibular afferents within the vestibular nucleus [73][74][75] , the expression of different glutamate receptors on vestibular nuclear neurons becomes a central issue in the understanding of vestibular function. The developmental profile of glutamate receptor subunits within the vestibular nuclei is therefore reviewed.…”

“…The developmental profile of glutamate receptor subunits within the vestibular nuclei is therefore reviewed. [75][76][77][78][79] . Infusion of NMDA antagonist into the vestibular nuclei of guinea pigs induced postural and oculomotor syndromes similar to those following vestibular deafferentation [80] , suggesting that in adult animals, NMDA receptor channels play essential roles in the maintenance of postural symmetry and eye position.…”

Receptors of Glutamate and Neurotrophin in Vestibular Neuronal Functions

“…Many in vivo and in vitro studies have shown that vestibular nuclear neurons are activated by primary vestibular afferent inputs via NMDA or AMPA receptors [83,86,101,150,155]. Electrophysiological recordings in adult rats and guinea pigs demonstrated that both the field potentials and EPSPs in second-order vestibular neurons were suppressed by specific AMPA and NMDA antagonists [39, 133,161].…”