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 Hartzell, H C Articles by Yoshikami, D Search for Related Content PubMed PubMed Citation Articles by Hartzell, H C Articles by Yoshikami, D

1. Post-synaptic responses to acetylcholine (ACh) released from nerve terminals and from iontophoretic micropipettes were investigated in skeletal muscle fibres of the snake. Each fibre has a compact end-plate consisting of fifty to seventy synaptic boutons. The fibres were voltage clamped, and synaptic currents were recorded from visually identified end-plates. 2. When acetylcholinesterase (AChE) is inhibited, a potentiating interaction is observed between two or more quanta that are released close to each other from a synaptic bouton and act upon partially overlapping postsynaptic areas. The potentiation is expressed as a prolongation of the synaptic current. This potentiation also occurs under normal conditions of release when about 300 quanta are distributed over the entire end-plate, so thet the presynaptic release sites are separated by an average of 2 mum. An analogous potentiating interaction is observed when micropipettes, closely apposed to the subsynaptic membrane, substitute for quantal release sites. ACh from one pipette potentiates the response to ACh from another pipette less than 2 mum away. 3. In contrast, with AChE fully active no post-synaptic potentiation is seen when the normal complement of quanta is released over the entire end-plate. The time course of the synaptic currents in response to a single quantum or to 300 quanta is similar. It is concluded that functionally the quanta act independently of each other, because AChE isolates each quantum from its neighbours by limiting the lifetime of ACh and its lateral diffusion in the synaptic cleft. The estimated area over which a quantum normally acts is less than 2mum2. 4. Post-synaptic receptors are not saturated by the ACh in a quantum, since the peak of the quantal response adds linearly to the response produced by an appropriate background concentration of ACh from a pipette. This conclusion is supported by the observation that upon inhibition of AChE the peak amplitude of the quantal current response increases by about 20% with no change in its time to peak. 5. It is suggested that post-synaptic potentiation between quanta may play a role in signalling at synapses in which non-linear dose-response characteristics have been observed and where transmitter is not as repidly inactivated as the neuromuscular synapse.

This article has been cited by other articles:

				J. S. Dittman and J. M. Kaplan Behavioral Impact of Neurotransmitter-Activated G-Protein-Coupled Receptors: Muscarinic and GABAB Receptors Regulate Caenorhabditis elegans Locomotion J. Neurosci., July 9, 2008; 28(28): 7104 - 7112. [Abstract] [Full Text] [PDF]

				S. Elenes, Y. Ni, G. D. Cymes, and C. Grosman Desensitization Contributes to the Synaptic Response of Gain-of-Function Mutants of the Muscle Nicotinic Receptor J. Gen. Physiol., November 1, 2006; 128(5): 615 - 627. [Abstract] [Full Text] [PDF]

				P. Ghildyal, D. Palani, and R. Manchanda Post- and prejunctional consequences of ecto-ATPase inhibition: electrical and contractile studies in guinea-pig vas deferens J. Physiol., September 1, 2006; 575(2): 469 - 480. [Abstract] [Full Text] [PDF]

				T.-i. Nishiki and G. J. Augustine Dual Roles of the C2B Domain of Synaptotagmin I in Synchronizing Ca2+-Dependent Neurotransmitter Release J. Neurosci., September 29, 2004; 24(39): 8542 - 8550. [Abstract] [Full Text] [PDF]

				E. Neher and T. Sakaba Combining Deconvolution and Noise Analysis for the Estimation of Transmitter Release Rates at the Calyx of Held J. Neurosci., January 15, 2001; 21(2): 444 - 461. [Abstract] [Full Text] [PDF]

				T. Sakaba and E. Neher Quantitative Relationship between Transmitter Release and Calcium Current at the Calyx of Held Synapse J. Neurosci., January 15, 2001; 21(2): 462 - 476. [Abstract] [Full Text] [PDF]

				J. S. Diamond and C. E. Jahr Synaptically Released Glutamate Does Not Overwhelm Transporters on Hippocampal Astrocytes During High-Frequency Stimulation J Neurophysiol, May 1, 2000; 83(5): 2835 - 2843. [Abstract] [Full Text] [PDF]

				M. R. Bennett Synaptic Transmission at Single Boutons in Sympathetic Ganglia Physiology, April 1, 2000; 15(2): 98 - 101. [Abstract] [Full Text] [PDF]

				S. Mennerick, W. Shen, W. Xu, A. Benz, K. Tanaka, K. Shimamoto, K. E. Isenberg, J. E. Krause, and C. F. Zorumski Substrate Turnover by Transporters Curtails Synaptic Glutamate Transients J. Neurosci., November 1, 1999; 19(21): 9242 - 9251. [Abstract] [Full Text] [PDF]

				M. H. Higgs and P. D. Lukasiewicz Glutamate Uptake Limits Synaptic Excitation of Retinal Ganglion Cells J. Neurosci., May 15, 1999; 19(10): 3691 - 3700. [Abstract] [Full Text] [PDF]

				J.J.B. Jack, D.M. Kullmann, A.U. Larkman, G. Major, and K.J. Stratford Quantal Analysis of Excitatory Synaptic Mechanisms in the Mammalian Central Nervous System Cold Spring Harb Symp Quant Biol, January 1, 1990; 55(0): 57 - 67. [Abstract] [PDF]

				C. Busch and B. Sakmann Synaptic Transmission in Hippocampal Neurons: Numerical Reconstruction of Quantal IPSCs Cold Spring Harb Symp Quant Biol, January 1, 1990; 55(0): 69 - 80. [Abstract] [PDF]

				H. C. Hartzell, S. W. Kuffler, and D. Yoshikami The Number of Acetylcholine Molecules in a Quantum and the Interaction between Quanta at the Subsynaptic Membrane of the Skeletal Neuromuscular Synapse Cold Spring Harb Symp Quant Biol, January 1, 1976; 40(0): 175 - 186. [Abstract] [PDF]