Document Detail

The dynamics of synchronized neurotransmitter release determined from compound spontaneous IPSCs in rat dentate granule neurones in vitro.
MedLine Citation:
PMID:  9705998     Owner:  NLM     Status:  MEDLINE    
1. The properties of GABAA receptor-mediated spontaneous IPSCs generated in hippocampal dentate granule neurones were analysed using whole-cell voltage-clamp techniques in order to explore the functional consequences of the low number (6-12) and close proximity of synaptic contacts made by single GABAergic interneurones. 2. Spontaneous IPSCs (sIPSCs) occurred with a frequency of 14.0 +/- 9.1 Hz (n = 31) and revealed a multi-modal positively skewed amplitude distribution (39.0 +/- 19.8 pA, median values). 3. The variance of 10-90% rise times and decay kinetics between IPSCs decreased with increasing peak amplitude. Larger amplitude events had significantly faster rise times, consistent with their site of generation being proximal to the soma. The decay kinetics of sIPSCs did not significantly change with amplitude. 4. Large amplitude sIPSCs occurred singularly or in discrete bursts, repeated regularly at low frequency. The rising phase of such sIPSCs were multi-phasic, composed of clear step-like inflections that were not a product of noise. The variability between the rising phase of individual sIPSCs was quantified by calculating their standard deviation, which produced fast rising (0.22 +/- 0.05 ms time to peak, n = 16) functions with half-widths of 0.38 +/- 0.10 ms, which declined to plateaux. 5. Computer simulations demonstrated that IPSCs with properties similar to those recorded experimentally could be generated by the linear summation of groups of temporally dispersed component events. Standard deviation functions of the rising phase of simulated IPSCs accurately described distributions of the temporal dispersion of unitary components. 6. The GABA uptake inhibitor (R)-N[4,4-bis(3-methyl-2-thienyl)but-3-enl-yl] nipecotic acid (tiagabine) (10 microM, n = 12) significantly prolonged the decay of mIPSCs (6.5 +/- 0.8 to 8.7 +/- 1.0 ms, median values) and sIPSCs (6.2 +/- 0.4 to 7.3 +/- 1.2 ms, median values), but failed to alter the frequency of occurrence, 10-90% rise times or peak amplitude of events. The application of flurazepam (30 microM, n = 7; 50 microM, n = 4) prolonged the decay of sIPSCs regardless of their amplitude. 7. These data indicate that sIPSCs are formed by the summation of unitary components that occur asynchronously and that GABA released from multiple sites has independent post-synaptic actions.
S R Williams; E H Buhl; I Mody
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of physiology     Volume:  510 ( Pt 2)     ISSN:  0022-3751     ISO Abbreviation:  J. Physiol. (Lond.)     Publication Date:  1998 Jul 
Date Detail:
Created Date:  1998-11-05     Completed Date:  1998-11-05     Revised Date:  2013-06-11    
Medline Journal Info:
Nlm Unique ID:  0266262     Medline TA:  J Physiol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  477-97     Citation Subset:  IM    
Reed Neurological Research Center, University of California Los Angeles School of Medicine, Department of Neurology 90095-1769, USA.
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MeSH Terms
Computer Simulation
Dentate Gyrus / cytology,  drug effects,  metabolism*
Electric Stimulation
Excitatory Postsynaptic Potentials / physiology*
GABA Modulators / pharmacology
GABA-A Receptor Agonists
GABA-A Receptor Antagonists
Membrane Potentials / physiology
Neurotransmitter Agents / metabolism*
Neurotransmitter Uptake Inhibitors / pharmacology
Patch-Clamp Techniques
gamma-Aminobutyric Acid / physiology
Grant Support
Reg. No./Substance:
0/GABA Modulators; 0/GABA-A Receptor Agonists; 0/GABA-A Receptor Antagonists; 0/Neurotransmitter Agents; 0/Neurotransmitter Uptake Inhibitors; 56-12-2/gamma-Aminobutyric Acid

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