Primary afferent excitatory transmission recorded intracellularly in vitro from rat medial vestibular neurons.
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.
Lewis
M R
MR
Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston 77550.
Phelan
K D
KD
Shinnick-Gallagher
P
P
Gallagher
J P
JP
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004558:Electric Stimulation; D066298:In Vitro Techniques; D007736:Kynurenic Acid / Q000494:pharmacology*; D008297:Male; D016202:N-Methylaspartate; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D017459:Receptors, Amino Acid; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000502:physiology*; D014726:Vestibular Nuclei / Q000187:drug effects / Q000502:physiology*
D017459:Receptors, Amino Acid; D011956:Receptors, Cell Surface; D001224:Aspartic Acid; D016202:N-Methylaspartate; D007736:Kynurenic Acid