QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

HOME  |   SEARCH  |   ARCHIVE  |   SUBSCRIBE  |   CONTACT  |   HELP

The Journal of Neuroscience, January 24, 2007, 27(4):942-950; doi:10.1523/JNEUROSCI.4996-06.2007

This Article Full Text Full Text (PDF) Supplemental Data Submit an eLetter Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Related articles in J. Neurosci. Similar articles in this journal Similar articles in ISI Web of Science 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 ISI Web of Science (6) Citing Articles via Google Scholar Google Scholar Articles by Alle, H. Articles by Geiger, J. R. P. Search for Related Content PubMed PubMed Citation Articles by Alle, H. Articles by Geiger, J. R. P.

 Previous Article  |  Next Article 

Cellular/Molecular
GABAergic Spill-Over Transmission onto Hippocampal Mossy Fiber Boutons

Henrik Alle and Jörg R. P. Geiger

Independent Hertie Research Group, Max Planck Institute for Brain Research, D-60528 Frankfurt, Germany

Correspondence should be addressed to Jörg R. P. Geiger, Independent Hertie Research Group, Max Planck Institute for Brain Research, Deutschordenstrasse 46, D-60528 Frankfurt, Germany. Email: geiger{at}mpih-frankfurt.mpg.de

Presynaptic ionotropic GABA_A receptors have been suggested to contribute to the regulation of cortical glutamatergic synaptic transmission. Here, we analyzed presynaptic GABA_A receptor-mediated currents (34°C) recorded from mossy fiber boutons (MFBs) in rat hippocampal slices. In MFBs from young and adult animals, GABA puff application activated currents that were blocked by GABA_A receptor antagonists. The conductance density of 0.65 mS · cm² was comparable to that of other presynaptic terminals. The single-channel conductance was 36 pS (symmetrical chloride), yielding an estimated GABA_A receptor density of 20–200 receptors per MFB. Presynaptic GABA_A receptors likely contain ₂-subunits as indicated by their zolpidem sensitivity. In accordance with the low apparent GABA affinity (EC₅₀ = 60 µM) of the receptors and a tight control of ambient GABA concentration by GABA transporters, no tonic background activation of presynaptic GABA_A receptors was observed. Instead, extracellular high-frequency stimulation led to transient presynaptic currents, which were blocked by GABA_A receptor antagonists but were enhanced by block of GAT 1 (GABA transporter 1), indicating that these currents were generated by GABA spill-over and subsequent presynaptic GABA_A receptor activation. Presynaptic spill-over currents were depressed by pharmacological cannabinoid 1 (CB1) receptor activation, suggesting that GABA was released predominantly by a CB1 receptor-expressing interneuron subpopulation. Because GABA_A receptors in axons are considered to act depolarizing, high activity of CB1 receptor-expressing interneurons will exert substantial impact on presynaptic membrane potential, thus modulating action potential-evoked transmitter release at the mossy fiber–CA3 synapse.

Key words: hippocampal mossy fiber; presynaptic; GABA_A receptor; spill-over; zolpidem; GAT

---

Received Nov. 17, 2006; revised Dec. 18, 2006; accepted Dec. 19, 2006.

Correspondence should be addressed to Jörg R. P. Geiger, Independent Hertie Research Group, Max Planck Institute for Brain Research, Deutschordenstrasse 46, D-60528 Frankfurt, Germany. Email: geiger{at}mpih-frankfurt.mpg.de

Related articles in J. Neurosci.:

This Week in The Journal

J. Neurosci. 2007 27: i. [Full Text]  

This article has been cited by other articles:

				R. Scott, A. Ruiz, C. Henneberger, D. M. Kullmann, and D. A. Rusakov Analog Modulation of Mossy Fiber Transmission Is Uncoupled from Changes in Presynaptic Ca2+ J. Neurosci., July 30, 2008; 28(31): 7765 - 7773. [Abstract] [Full Text] [PDF]

				G. J. Kress, M. J. Dowling, J. P. Meeks, and S. Mennerick High Threshold, Proximal Initiation, and Slow Conduction Velocity of Action Potentials in Dentate Granule Neuron Mossy Fibers J Neurophysiol, July 1, 2008; 100(1): 281 - 291. [Abstract] [Full Text] [PDF]

				F. F. Trigo, M. Chat, and A. Marty Enhancement of GABA Release through Endogenous Activation of Axonal GABAA Receptors in Juvenile Cerebellum J. Neurosci., November 14, 2007; 27(46): 12452 - 12463. [Abstract] [Full Text] [PDF]

				B. M. Stell, P. Rostaing, A. Triller, and A. Marty Activation of Presynaptic GABAA Receptors Induces Glutamate Release from Parallel Fiber Synapses J. Neurosci., August 22, 2007; 27(34): 9022 - 9031. [Abstract] [Full Text] [PDF]

				M. Uchigashima, M. Fukaya, M. Watanabe, and H. Kamiya Evidence against GABA Release from Glutamatergic Mossy Fiber Terminals in the Developing Hippocampus J. Neurosci., July 25, 2007; 27(30): 8088 - 8100. [Abstract] [Full Text] [PDF]

Home  |   Search  |   Archive  |   Subscribe  |   Contact  |   Help