Séminaire - Rafael GutiérrezBlueprint of the connection between the dentate gyrus and CA310 févr. 2017 à 11:30 (CGFB campus Carreire)
The mossy fibers, the axons of the granule cells of the dentate gyrus, innervate interneurons and pyramidal cells of the CA3 area of the hippocampus. These fibers use glutamate (and also GABA during development) for fast chemical transmission, but in the adult they are mainly excitatory.
Surprisingly however, we found functional and anatomical evidence of gap junctions formed by connexin 36 (Cx36) in the mossy fibers establishing synapses with some pyramidal cells. Thus, we proposed the existence of mixed electrical-chemical transmission between the principal cells of these two hippocampal substructures. Interestingly, the incidence of pyramidal cells receiving mixed neurotransmission as determined by electrophysiology was very low, whereas immunohistological and single cell-PCR studies have revealed a profuse expression of Cx36 in the granule cells and their mossy fibers.
Current work in my lab has disclosed an underlying electrical network between the mossy fibers and pyramidal cells of CA3 that is virtually tonically closed but that can be turned on, enabling the co-existence and, thus, a reciprocal modulation of
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Beltrán J.Q, Gutiérrez, R. Co-release of glutamate and GABA from single, identified mossy fiber giant boutons. J. Physiol. 590: 4789-4800, 2012.
Hamzei-Sichani, F. et al. Mixed electrical–chemical synapses in adult rat hippocampus are primarily glutamatergic and coupled by connexin-36. Frontiers in Neuroanatomy 6, Art. 13, 1-26, 2012
Osorio B, León U, Galván EJ, Gutiérrez R. Cocultures of GFP(+)-granule cells with GFP(-) -pyramidal cells and interneurons for the study of mossy fiber neurotransmission with paired recordings. Hippocampus 23(4):247-52, 2013.
Münster-Wandowski A, Gómez-Lira G, Gutiérrez R. Mixed neurotransmission in the hippocampal mossy fibers. Front. Cell. Neurosci. 22;7:210, 2013.
Gutiérrez, R. The plastic neurotransmitter phenotype of the hippocampal granule cells and of the moss in their messy fibers. J. Chem. Neuroanat. 2015 doi: 10.1016/
j.jchemneu. 2015.11.007. Galván EJ, Pérez-Rosello T, Gómez-Lira G, Lara E, Gutiérrez R, Barrionuevo G. Synapse-specific compartmentalization of signaling cascades for LTP induction in CA3 interneurons. Neuroscience 290:332-345, 2015
Galván EJ, Gutiérrez, R. Target-Dependent Compartmentalization of the Corelease of Glutamate and GABA from the Mossy Fibers. J. Neurosci. 37: 701-714, 2017