HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Barnes-Davies, M Articles by Forsythe, I D Search for Related Content PubMed PubMed Citation Articles by Barnes-Davies, M Articles by Forsythe, I D

Department of Cell Physiology and Pharmacology, University of Leicester, UK.

1. Whole-cell patch recordings were used to examine the EPSC generated by the calyx of Held in neurones of the medial nucleus of the trapezoid body (MNTB). Each neurone receives a somatic input from a single calyx (giant synapse). 2. A slow NMDA receptor-mediated EPSC peaked in 10 ms and decayed as a double exponential with time constants of 44 and 147 ms. A fast EPSC had a mean rise time of 356 microseconds (at 25 degrees C), while the decay was described by a double exponential with time constants of 0.70 and 3.43 ms. 3. Cyclothiazide slowed the decay of the fast EPSC, indicating that it is mediated by AMPA receptors. The slower time constant was slowed to a greater extent than the faster time constant. Cyclothiazide potentiated EPSC amplitude, partly by a presynaptic mechanism. 4. The metabotropic glutamate receptor (mGluR) agonists, 1S,3S-ACPD, 1S,3R-ACPD and L-2-amino-4-phosphonobutyrate (L-AP4) reversibly depressed EPSC amplitude. A dose-response curve for 1S,3S-ACPD gave an EC50 of 7 microM and a Hill coefficient of 1.2. 5. Analysis of the coefficient of variation ratio showed that the above mGluR agonists acted presynaptically to reduce the probability of transmitter release. Adenosine and baclofen also depressed transmission by a presynaptic mechanism. 6. alpha-Methyl-4-carboxyphenylglycine (MCPG; 0.5-1 mM) did not antagonize the effects of 1S,3S-ACPD, while high concentrations of L-2-amino-3-phosphonopropionic acid (L-AP3; 1 mM) and 4-carboxy-3-hydroxyphenyglycine (4C3HPG; 500 microM) depressed transmission. 7. There was a power relationship between [Ca2+]o and EPSC amplitude with co-operativity values ranging from 1.5 to 3.4. 8. The mechanism by which mGluRs modulate transmitter release appeared to be independent of presynaptic Ca2+ or K+ currents, since ACPD caused no change in the level of paired-pulse facilitation or the duration of the presynaptic action potential (observed by direct recording from the terminal), indicating that the presynaptic mGluR transduction mechanism may be coupled to part of the exocytotic machinery. 9. Our data are not consistent with the presence at the calyx of Held of any one known mGluR subtype. Comparison of the time course and pharmacology of the fast EPSC with data from cloned AMPA receptors is consistent with the idea that GluR-Do subunits dominate the postsynaptic channels.

This article has been cited by other articles:

				E. M. Silinsky Selective disruption of the mammalian secretory apparatus enhances or eliminates calcium current modulation in nerve endings PNAS, April 29, 2008; 105(17): 6427 - 6432. [Abstract] [Full Text] [PDF]

				J. Hermann, M. Pecka, H. von Gersdorff, B. Grothe, and A. Klug Synaptic Transmission at the Calyx of Held Under In Vivo-Like Activity Levels J Neurophysiol, August 1, 2007; 98(2): 807 - 820. [Abstract] [Full Text] [PDF]

				K. M. MacLeod, T. K. Horiuchi, and C. E. Carr A Role for Short-Term Synaptic Facilitation and Depression in the Processing of Intensity Information in the Auditory Brain Stem J Neurophysiol, April 1, 2007; 97(4): 2863 - 2874. [Abstract] [Full Text] [PDF]

				M. G. Moldavan, R. P. Irwin, and C. N. Allen Presynaptic GABAB Receptors Regulate Retinohypothalamic Tract Synaptic Transmission by Inhibiting Voltage-Gated Ca2+ Channels J Neurophysiol, June 1, 2006; 95(6): 3727 - 3741. [Abstract] [Full Text] [PDF]

				A. Y. C. Wong, B. Billups, J. Johnston, R. J. Evans, and I. D. Forsythe Endogenous Activation of Adenosine A1 Receptors, but Not P2X Receptors, During High-Frequency Synaptic Transmission at the Calyx of Held J Neurophysiol, June 1, 2006; 95(6): 3336 - 3342. [Abstract] [Full Text] [PDF]

				Y. Lu and E. W Rubel Activation of Metabotropic Glutamate Receptors Inhibits High-Voltage-Gated Calcium Channel Currents of Chicken Nucleus Magnocellularis Neurons J Neurophysiol, March 1, 2005; 93(3): 1418 - 1428. [Abstract] [Full Text] [PDF]

				B. Lin, F. A. Brucher, L. L. Colgin, and G. Lynch Long-Term Potentiation Alters the Modulator Pharmacology of AMPA-Type Glutamate Receptors J Neurophysiol, June 1, 2002; 87(6): 2790 - 2800. [Abstract] [Full Text] [PDF]