PTP and LTP at a hippocampal mossy fiber-interneuron synapse Journal Article

Author(s): Alle, Henrik ; Jonas, Peter; Geiger, Jörg R
Article Title: PTP and LTP at a hippocampal mossy fiber-interneuron synapse
Abstract: The mossy fiber-CA3 pyramidal neuron synapse is a main component of the hippocampal trisynaptic circuitry. Recent studies, however, suggested that inhibitory interneurons are the major targets of the mossy fiber system. To study the regulation of mossy fiber-interneuron excitation, we examined unitary and compound excitatory postsynaptic currents in dentate gyrus basket cells, evoked by paired recording between granule and basket cells or extracellular stimulation of mossy fiber collaterals. The application of an associative high-frequency stimulation paradigm induced posttetanic potentiation (PTP) followed by homosynaptic long-term potentiation (LTP). Analysis of numbers of failures, coefficient of variation, and paired-pulse modulation indicated that both PTP and LTP were expressed presynaptically. The Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA) did not affect PTP or LTP at a concentration of 10 mM but attenuated LTP at a concentration of 30 mM. Both forskolin, an adenylyl cyclase activator, and phorbolester diacetate, a protein kinase C stimulator, lead to a long-lasting increase in excitatory postsynaptic current amplitude. H-89, a protein kinase A inhibitor, and bisindolylmaleimide, a protein kinase C antagonist, reduced PTP, whereas only bisindolylmaleimide reduced LTP. These results may suggest a differential contribution of protein kinase A and C pathways to mossy fiber-interneuron plasticity. Interneuron PTP and LTP may provide mechanisms to maintain the balance between synaptic excitation of interneurons and that of principal neurons in the dentate gyrus-CA3 network.
Keywords: Animals; Rats; Chelating Agents/pharmacology; Rats, Wistar; Synapses/physiology; Synapses/drug effects; Mossy Fibers, Hippocampal/physiology; Adenylate Cyclase/metabolism; Cyclic AMP-Dependent Protein Kinases/antagonists & inhibitors; Cyclic AMP-Dependent Protein Kinases/metabolism; Egtazic Acid/analogs & derivatives; Egtazic Acid/pharmacology; Enzyme Inhibitors/pharmacology; Forskolin/pharmacology; Indoles/pharmacology; Interneurons/drug effects; Interneurons/physiology: Isoquinolines/pharmacology; Long-Term Potentiation/drug effects; Long-Term Potentiation/physiology; Maleimides/pharmacology; Mossy Fibers, Hippocampal/drug effects; Phorbol Esters/pharmacology; Protein Kinase C/antagonists & inhibitors; Protein Kinase C/metabolism; Sulfonamides
Journal Title: PNAS
Volume: 98
Issue 25
ISSN: 1091-6490
Publisher: National Academy of Sciences  
Date Published: 2001-12-04
Start Page: 14708
End Page: 14713
DOI: 10.1073/pnas.251610898
Open access: yes (repository)