AMPA receptors with high Ca2+ permeability mediate synaptic transmission in the avian auditory pathway.

AUTOR(ES)

Otis, T S

RESUMO

1. The permeability of AMPA (alpha-amino-3-hydroxy-5-methyl-4- isoxazolepropionate) receptors in the chick cochlear nucleus, the nucleus magnocellularis (nMAG), was examined by measuring the shift in reversal potential (Erev) of current through glutamate or neurotransmitter-gated channels in solutions of different ionic composition. 2. Outwardly rectifying glutamate-activated currents in outside-out membrane patches showed rapid activation and desensitization. The Erev of glutamate-evoked current in zero sodium solutions was dependent on the extracellular Ca2+ concentration. The relation between Erev and Ca2+ ionic activities could be described by the Goldman-Hodgkin-Katz equation with a permeability ratio, PCa/PCs, of 3.3. The PNa/PCs was estimated as 0.66, indicating a PCa/PNa of 5. 3. Evoked excitatory postsynaptic currents (EPSCs) could be recorded during local perfusion of the auditory nerve-nMAG synapse with isotonic Ca2+. The Erev of the EPSC shifted in the positive direction in high-Ca2+ solution as predicted from the preceding analysis. The fraction of current carried by Ca2+ during the AMPA receptor EPSC was estimated as 18%.

Documentos Relacionados

• The peptide CGRP increases a high-threshold Ca2+ current in rat nodose neurones via a pertussis toxin-sensitive pathway.
• P-type Ca2+ channels mediate excitatory and inhibitory synaptic transmitter release in crayfish muscle.
• Characterization of Ca2+ signals induced in hippocampal CA1 neurones by the synaptic activation of NMDA receptors.
• Ca2+-permeable AMPA receptors in central neurons
• Ca2+ transients in cardiac myocytes measured with high and low affinity Ca2+ indicators.