Non-calyceal excitatory inputs mediate low fidelity synaptic transmission in rat auditory brainstem slices.
Principal neurons of the medial nucleus of the trapezoid body (MNTB) receive a synaptic input from a single giant calyx terminal that generates a fast-rising, large excitatory postsynaptic current (EPSC), each of which are supra-threshold for postsynaptic action potential generation. Here, we present evidence that MNTB principal neurons receive multiple excitatory synaptic inputs generating slow-rising, small EPSCs that are also capable of triggering postsynaptic action potentials but are of non-calyceal origin. Both calyceal and non-calyceal EPSCs are mediated by alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) and N-methyl-d-aspartate (NMDA) receptor activation; however, the NMDA receptor-mediated response is proportionally larger at the non-calyceal synapses. Non-calyceal synapses generate action potentials in MNTB principal neurons with a longer latency and a lower reliability than the large calyceal input. They constitute an alternative low fidelity synaptic input to the fast and secure relay transmission via the calyx of Held synapse.
Hamann
Martine
M
Department of Cell Physiology and Pharmacology, University of Leicester, PO Box 138, Leicester LE1 9HN, UK. mh86@le.ac.uk
Billups
Brian
B
Forsythe
Ian D
ID
D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D001306:Auditory Pathways / Q000502:physiology*; D001933:Brain Stem / Q000166:cytology / Q000502:physiology*; D004558:Electric Stimulation; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000145:classification / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques / Q000379:methods; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology; D013997:Time Factors; D014633:Valine / Q000031:analogs & derivatives* / Q000494:pharmacology; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
D000779:Anesthetics, Local; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D011810:Quinoxalines; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; D013779:Tetrodotoxin; C056639:2-amino-5-phosphopentanoic acid; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D014633:Valine