title: Synergy between electrical coupling and membrane properties promotes strong synchronization of neurons of the mesencephalic trigeminal nucleus.
abstract: Electrical synapses are known to form networks of extensively coupled neurons in various regions of the mammalian brain. The mesencephalic trigeminal (MesV) nucleus, formed by the somata of primary afferents originating in jaw-closing muscles, constitutes one of the first examples supporting the presence of electrical synapses in the mammalian CNS; however, the properties, functional organization, and developmental emergence of electrical coupling within this structure remain unknown. By combining electrophysiological, tracer coupling, and immunochemical analysis in brain slices of rat and mouse, we found that coupling is mostly restricted to pairs or small clusters of MesV neurons. Electrical transmission is supported by connexin36 (Cx36)-containing gap junctions at somato-somatic contacts where only a small proportion of channels appear to be open (∼0.1%). In marked contrast with most brain structures, coupling among MesV neurons increases with age, such that it is absent during early development and appears at postnatal day 8. Interestingly, the development of coupling parallels the development of intrinsic membrane properties responsible for repetitive firing in these neurons. We found that, acting together, sodium and potassium conductances enhance the transfer of signals with high-frequency content via electrical synapses, leading to strong spiking synchronization of the coupled neurons. Together, our data indicate that coupling in the MesV nucleus is restricted to mostly pairs of somata between which electrical transmission is supported by a surprisingly small fraction of the channels estimated to be present, and that coupling synergically interacts with specific membrane conductances to promote synchronization of these neurons.
authors.affiliation: Laboratorio de Neurofisiología Celular, Departamento de Fisiología, Facultad de Medicina, Universidad de la República, Montevideo 11800, Uruguay. scurti@fmed.edu.uy
authors.forename: Sebastian
authors.initials: S
authors.lastname: Curti
authors.forename: Gregory
authors.initials: G
authors.lastname: Hoge
authors.forename: James I
authors.initials: JI
authors.lastname: Nagy
authors.forename: Alberto E
authors.initials: AE
authors.lastname: Pereda
mesh_terms: D000818:Animals; D001921:Brain / Q000254:growth & development / Q000378:metabolism / Q000502:physiology; D002450:Cell Communication / Q000502:physiology*; D017630:Connexins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D054351:Electrical Synapses / Q000502:physiology*; D017629:Gap Junctions / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D066298:In Vitro Techniques; D008469:Meclofenamic Acid / Q000494:pharmacology; D008564:Membrane Potentials / Q000502:physiology; D008636:Mesencephalon / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D057054:Molecular Imaging / Q000379:methods; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D013570:Synaptic Membranes / Q000378:metabolism / Q000502:physiology*; D014278:Trigeminal Nuclei / Q000166:cytology / Q000502:physiology*; D000097004:Gap Junction delta-2 Protein
chemical_list: D017630:Connexins; D008469:Meclofenamic Acid; D000097004:Gap Junction delta-2 Protein