Gap-junctional communication between neurons was first described several decades ago in crayfish, and was later studied by electrophysiological means in mammals. This field of research gained new momentum when the connexin 36 (Cx36) gene was discovered and its neuronal expression characterized.
It is now clear that gap junctions between neurons (also called electrical synapses) are abundant postnatally and are even expressed in certain areas of the adult brain, including the retina. They seem to fulfil distinct functions that are independent of, but possibly modulated by, chemical synapses.
In addition to Cx36, Cx45 and Cx57 expression have also been shown in certain types of mouse neuron. Recently, pannexin 1 and 2 were also shown to be expressed in certain types of central neuron in rodents and to form gap junction channels — at least after exogenous expression — in Xenopus laevis oocytes.
Identification of the expression pattern of connexins in neurons was greatly eased by analysis with reporter genes, which can be expressed in trangenic mice instead of the corresponding connexin gene.
During recent years, neuronal gap junctions have been characterized or postulated to be expressed in several adult brain regions, including the neocortex, thalamus, inferior olive, cerebellum and retina.
The characterization of transgenic mouse mutants deficient in CX36 showed that gamma frequency network oscilliations between hippocampal interneurons were disrupted in such mutants and that night vision was compromised. The same decrease in the b-wave in the electroretinogram was found in CX36-deficient mice and in neuronally CX45-deficient mice, which, together with immunochemical evidence, indicates that these connexins form heterotypic gap junction channels between AII amacrine cells and ON-cone bipolar cells.
Gap junctions are channel-forming structures in contacting plasma membranes that allow direct metabolic and electrical communication between almost all cell types in the mammalian brain. At least 20 connexin genes and 3 pannexin genes probably code for gap junction proteins in mice and humans. Gap junctions between murine neurons (also known as electrical synapses) can be composed of connexin 36, connexin 45 or connexin 57 proteins, depending on the type of neuron. Furthermore, pannexin 1 and 2 are likely to form electrical synapses. Here, we discuss the roles of connexin and pannexin genes in the formation of neuronal gap junctions, and evaluate recent functional analyses of electrical synapses that became possible through the characterization of mouse mutants that show targeted defects in connexin genes.
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Bennett, M. V. L. in Handbook of Physiology Sect. I Vol. 1 (ed. Kandel, E. R.) 357–416 (Williams and Wilkins, Baltimore, Maryland, 1977).
Kumar, N. M. & Gilula, N. B. The gap junction communication channel. Cell 84, 381–388 (1996).
Söhl, G. & Willecke, K. An update on connexin genes and their nomenclature in mouse and man. Cell Commun. Adhes. 10, 173–180 (2003).
Söhl, G., Odermatt, B., Maxeiner, S., Degen, J. & Willecke, K. New insights into the expression and function of neural connexins with transgenic mouse mutant. Brain Res. Brain Res. Rev. 47, 245–259 (2004).
Evans, W. H. & Martin, P. E. Gap junctions: structure and function (Review). Mol. Membr. Biol. 19, 121–136 (2002).
Lampe, P. D. & Lau, A. F. Regulation of gap junctions by phosphorylation of connexins. Arch. Biochem. Biophys. 384, 205–215 (2000).
Lampe, P. D. & Lau, A. F. The effects of connexin phosphorylation on gap junctional communication. Int. J. Biochem. Cell Biol. 36, 1171–1186 (2004).
Nagy, J. I., Dudek, F. E. & Rash, J. E. Update on connexins and gap junctions in neurons and glia in the mammalian nervous system. Brain Res. Brain Res. Rev. 47, 191–215 (2004).
Furshpan, E. J. & Potter, D. D. Transmission at the giant motor synapses of the crayfish. J. Physiol. (Lond.) 145, 289–325 (1959).
Korn, H., Sotelo, C. & Crepel, F. Electronic coupling between neurons in the rat lateral vestibular nucleus. Exp. Brain Res. 16, 255–275 (1973).
Connors, B. W. & Long, M. A. Electrical synapses in the mammalian brain. Annu. Rev. Neurosci. 27, 393–418 (2004).
Bennett, M. V. & Zukin, R. S. Electrical coupling and neuronal synchronization in the mammalian brain. Neuron 41, 495–511 (2004). Provides a comprehensive explanation and definition of low-pass filter characteristics.
Hormuzdi, S. G., Filippov, M. A., Mitropoulou, G., Monyer, H. & Bruzzone, R. Electrical synapses: a dynamic signaling system that shapes the activity of neuronal networks. Biochim. Biophys. Acta 1662, 113–137 (2004).
Alvarez-Maubecin, V., Garcia-Hernandez, F., Williams, J. T. & Van Bockstaele, E. J. Functional coupling between neurons and glia. J. Neurosci. 20, 4091–4098 (2000).
Pakhotin, P. & Verkhratsky, A. Electrical synapses between Bergmann glia cells and Purkinje neurons in rat cerebellar slices. Mol. Cell. Neurosci. 28, 79–84 (2005).
Gibson, J. R., Beierlein, M. & Connors, B. W. Functional properties of electrical synapses between inhibitory interneurons of neocortical layer 4. J. Neurophysiol. 93, 467–480 (2005).
Buzsaki, G. & Chrobak, J. J. Temporal structure in spatially organized neuronal ensembles: a role for interneuronal networks. Curr. Opin. Neurobiol. 5, 504–510 (1995).
Fricker, D. & Miles, R. Interneurons, spike timing, and perception. Neuron 32, 771–774 (2001).
Smith, M. & Pereda, A. E. Chemical synaptic activity modulates nearby electrical synapses. Proc. Natl Acad. Sci. USA 100, 4849–4854 (2003).
Pereda, A. E., Rash, J. E., Nagy, J. I. & Bennett, M. V. Dynamics of electrical transmission at club endings on the Mauthner cells. Brain Res. Brain Res. Rev. 47, 227–244 (2004).
Iacobas, D. A. et al. Sensitivity of the brain transcriptome to connexin ablation. Biochem. Biophys. Acta 22 Dec 2004 (10.1016/j.bbamem.2004.12.002).
Filippov, M. A., Hormuzdi, S. G., Fuchs, E. C. & Monyer, H. A reporter allele for investigating connexin 26 gene expression in the mouse brain. Eur. J. Neurosci. 18, 3183–3192 (2003).
Söhl, G., Güldenagel, M., Traub, O. & Willecke, K. Connexin expression in the retina. Brain Res. Brain Res. Rev. 32, 138–145 (2000).
Dermietzel, R. et al. Differential expression of three gap junction proteins in developing and mature brain tissues. Proc. Natl Acad. Sci. USA 86, 10148–10152 (1989).
Condorelli, D. F. et al. Cloning of a new gap junction gene (Cx36) highly expressed in mammalian brain neurons. Eur. J. Neurosci. 10, 1202–1208 (1998).
Söhl, G., Degen, J., Teubner, B. & Willecke, K. The murine gap junction gene connexin36 is highly expressed in mouse retina and regulated during brain development. FEBS Lett. 428, 27–31 (1998).
Maxeiner, S. et al. Spatiotemporal transcription of connexin45 during brain development results in neuronal expression in adult mice. Neuroscience 119, 689–700 (2003).
Maxeiner, S. & Dedek, K. et al. Deletion of connexin45 in mouse retinal neurons disrupts rod/cone signaling pathway between AII amacrine and ON cone bipolar cells and leads to impaired visual transmission. J. Neurosci. 25, 566–576 (2005). This study reports results that are similar to those obtained from CX36-deficient mice (see reference 35). Both CX36- and CX45-knockout studies indicate that CX36 and CX45 form heterotypic electrical synapses between AII amacrine and ON cone bipolar cells.
Hombach, S. et al. Functional expression of connexin57 in horizontal cells of the mouse retina. Eur. J. Neurosci. 19, 2633–2640 (2004).
Bruzzone, R., Hormuzdi, S. G., Barbe, M. T., Herb, A. & Monyer, H. Pannexins, a family of gap junction proteins expressed in brain. Proc. Natl Acad. Sci. USA 100, 13644–13649 (2003).
Condorelli, D. F., Belluardo, N., Trovato-Salinaro, A. & Mudo, G. Expression of Cx36 in mammalian neurons. Brain Res. Brain Res. Rev. 32, 72–85 (2000).
Belluardo, N. et al. Expression of connexin36 in the adult and developing rat brain. Brain Res. 865, 121–138 (2000).
Teubner, B. et al. Functional expression of the murine connexin36 gene coding for a neuron-specific gap junctional protein. J. Membr. Biol. 176, 249–262 (2000).
Deans, M. R., Gibson, J. R., Sellitto, C., Connors, B. W. & Paul, D. L. Synchronous activity of inhibitory networks in neocortex requires electrical synapses containing connexin36. Neuron 31, 477–485 (2001). Shows that rhythmic inhibitory potentials generated by low-threshold spiking interneurons of the neocortex could be induced, but show weak synchrony.
Güldenagel, M. et al. Visual transmission deficits in mice with targeted disruption of the gap junction gene connexin36. J. Neurosci. 21, 6036–6044 (2001). In this study, the disruption of the Cx36 gene led to a reduction of the b-wave and indicated that the heterologous gap junction coupling between AII amacrine cells and ON cone bipolar cells is impaired in CX36-impaired mice.
Hormuzdi, S. G. et al. Impaired electrical signaling disrupts gamma frequency oscillations in connexin 36-deficient mice. Neuron 31, 487–495 (2001). According to this report, targeted deletion of Cx36 does not abolish the gamma network oscillations but does reduce their synchrony and overall power.
Degen, J. et al. Expression pattern of lacZ reporter gene representing connexin36 in transgenic mice. J. Comp. Neurol. 473, 511–525 (2004).
Long, M. A., Deans, M. R., Paul, D. L. & Connors, B. W. Rhythmicity without synchrony in the electrically uncoupled inferior olive. J. Neurosci. 22, 10898–10905 (2002).
Kistler W. M. et al. Analysis of Cx36 knockout does not support tenet that olivary gap junctions are required for complex spike synchronization and normal motor performance. Ann. NY Acad. Sci. 978, 391–404 (2002).
De Zeeuw, C. I. et al. Deformation of network connectivity in the inferior olive of connexin 36-deficient mice is compensated by morphological and electrophysiological changes at the single neuron level. J. Neurosci. 23, 4700–4711 (2003).
Frisch, C. et al. Memory impairment but no changes in brain cholinergic and monoaminergic levels after deletion of the neuronal gap junction protein connexin36 in mice. Behav. Brain Res. 157, 177–185 (2005).
Kistler, W. M. & De Zeeuw, C. I. Dynamical working memory and timed responses: the role of reverberating loops in the olivo-cerebellar system. Neural Comput. 14, 2597–2626 (2002).
Placantonakis, D. G., Bukovsky, A. A., Zeng, X. H., Kiem, H. P. & Welsh, J. P. Fundamental role of inferior olive connexin 36 in muscle coherence during tremor. Proc. Natl Acad. Sci. USA 101, 7164–7169 (2004).
Mann-Metzer, P. & Yarom, Y. Electrotonic coupling interacts with intrinsic properties to generate synchronized activity in cerebellar networks of inhibitory interneurons. J. Neurosci. 19, 3298–3306 (1999).
Cheron, G. et al. Inactivation of calcium-binding protein genes induces 160 Hz oscillations in the cerebellar cortex of alert mice. J. Neurosci. 24, 434–441 (2004).
Suzuki, W. A. Episodic memory signals in the rat hippocampus. Neuron 40, 1055–1056 (2003).
Dash, P. K., Hebert, A. E. & Runyan, J. D. A unified theory for systems and cellular memory consolidation. Brain Res. Brain Res. Rev. 45, 30–37 (2004).
Buzsaki, G., Buhl, D. L., Harris, K. D., Csicsvari, J., Czeh, B. & Morozov, A. Hippocampal network patterns of activity in the mouse. Neuroscience 116, 201–211 (2003).
Venance, L. et al. Connexin expression in electrically coupled postnatal rat brain neurons. Proc. Natl Acad. Sci. USA 97, 10260–10265 (2000).
Buhl, D. L., Harris, K. D., Hormuzdi, S. G., Monyer, H. & Buzsaki, G. Selective impairment of hippocampal gamma oscillations in connexin-36 knock-out mouse in vivo. J. Neurosci. 23, 1013–1018 (2003).
Maier, N. et al. Reduction of high-frequency network oscillations (ripples) and pathological network discharges in hippocampal slices from connexin 36-deficient mice. J. Physiol (Lond.). 541, 521–528 (2002).
Condorelli, D. F., Trovato-Salinaro, A., Mudo, G., Mirone, M. B. & Belluardo, N. Cellular expression of connexins in the rat brain: neuronal localization, effects of kainate-induced seizures and expression in apoptotic neuronal cells. Eur. J. Neurosci. 18, 1807–1827 (2003).
Panchin, Y. et al. A ubiquitous family of putative gap junction molecules. Curr. Biol. 10, R473–R474 (2000).
Bao, L., Locovei, S. & Dahl, G. Pannexin membrane channels are mechanosensitive conduits for ATP. FEBS Lett. 572, 65–68 (2004).
Traub, R. D. & Bibbig, A. A model of high-frequency ripples in the hippocampus based on synaptic coupling plus axon-axon gap junctions between pyramidal neurons. J. Neurosci. 20, 2086–2093 (2000).
Traub, R. D. et al. Axonal gap junctions between principal neurons: a novel source of network oscillations, and perhaps epileptogenesis. Rev. Neurosci. 13, 1–30 (2002).
Traub, R. D., Bibbig, A., LeBeau, F. E., Buhl, E. H. & Whittington, M. A. Cellular mechanisms of neuronal population oscillations in the hippocampus in vitro. Annu. Rev. Neurosci. 27, 247–278 (2004).
Draguhn, A., Traub, R. D., Schmitz, D. & Jefferys, J. G. Electrical coupling underlies high-frequency oscillations in the hippocampus in vitro. Nature 394, 189–192 (1998).
Schmitz, D. et al. Axo–axonal coupling. A novel mechanism for ultrafast neuronal communication. Neuron 31, 831–840 (2001). Reports dye coupling between putative axons of principal cells, as shown by confocal laser scanning micoscropy.
Spruston N. Axonal gap junctions send ripples through the hippocampus. Neuron 31, 669–671 (2001).
Maier, N., Nimmrich, V. & Draguhn, A. Cellular and network mechanisms underlying spontaneous sharp wave–ripple complexes in mouse hippocampal slices. J. Physiol. (Lond.) 550, 873–887 (2003).
Towers, S. K. et al. Fast network oscillations in the rat dentate gyrus in vitro. J. Neurophysiol. 87, 1165–1168 (2002).
LeBeau, F. E., Towers, S. K., Traub, R. D., Whittington, M. A. & Buhl, E. H. Fast network oscillations induced by potassium transients in the rat hippocampus in vitro. J. Physiol. (Lond.) 542, 167–179 (2002).
Pais, I. et al. Sharp-wave like activity in hippocampus in vitro in mice lacking the gap junction protein connexin 36. J. Neurophysiol. 89, 2046–2054 (2003).
Gillies, M. J. et al. A model of atropine-resistant theta oscillations in rat hippocampal area CA1. J. Physiol. (Lond.) 543, 779–793 (2002).
Blatow, M. et al. A novel network of multipolar bursting interneurons generates theta frequency oscillations in neocortex. Neuron 38, 805–817 (2003).
Montoro, R. J. & Yuste, R. Gap junctions in developing neocortex: a review. Brain Res. Brain Res. Rev. 47, 216–226 (2004).
Galarreta, M. & Hestrin, S. Spike transmission and synchrony detection in networks of GABAergic interneurons. Science 292, 2295–2299 (2001).
Fukuda, T. & Kosaka, T. Ultrastructural study of gap junctions between dendrites of parvalbumin-containing GABAergic neurons in various neocortical areas of the adult rat. Neuroscience 120, 5–20 (2003).
Beierlein, M., Gibson, J. R. & Connors, B. W. A network of electrically coupled interneurons drives synchronized inhibition in neocortex. Nature Neurosci. 3, 904–910 (2000).
Szabadics, J., Lorincz, A. & Tamas, G. Beta and gamma frequency synchronization by dendritic GABAergic synapses and gap junctions in a network of cortical interneurons. J. Neurosci. 21, 5824–5831 (2001).
Liu, X. B. & Jones, E. G. Fine structural localization of connexin-36 immunoreactivity in mouse cerebral cortex and thalamus. J. Comp. Neurol. 466, 457–467 (2003).
Landisman, C. E. et al. Electrical synapses in the thalamic reticular nucleus. J. Neurosci. 22, 1002–1009 (2002).
Long, M. A., Landisman, C. E. & Connors, B. W. Small clusters of electrically coupled neurons generate synchronous rhythms in the thalamic reticular nucleus. J. Neurosci. 24, 341–349 (2004).
Usrey, W. M. Spike timing and visual processing in the retinogeniculocortical pathway. Philos. Trans. R. Soc. Lond. B 357, 1729–1737 (2002).
Hughes, S. W. et al. Synchronized oscillations at alpha and theta frequencies in the lateral geniculate nucleus. Neuron 42, 253–268 (2004). Showed that high-threshold bursts or burstlets are groups of spikelets with properties of electrotonically transmitted action potentials that are accompanied by dye coupling and abolished by the gap junction blocker CBX.
Cook, J. D. & Becker, E. L. Gap junctions in the vertebrate retina. Microsc. Res. Tech. 31, 408–419 (1995).
Feigenspan, A., Teubner, B., Willecke, K. & Weiler, R. Expression of neuronal connexin36 in AII amacrine cells of the mammalian retina. J. Neurosci. 21, 230–239 (2001).
Mills, S. L., O'Brien, J. J., Li, W., O'Brien, J. & Massey, S. C. Rod pathways in the mammalian retina use connexin 36. J. Comp. Neurol. 436, 336–350 (2001).
Lee, E. J. et al. The immunocytochemical localization of connexin 36 at rod and cone gap junctions in the guinea pig retina. Eur. J. Neurosci. 18, 2925–2934 (2003).
Feigenspan, A. et al. Expression of connexin36 in cone pedicles and OFF-cone bipolar cells of the mouse retina. J. Neurosci. 24, 3325–3334 (2004).
Hidaka, S., Akahori, Y. & Kurosawa, Y. Dendrodendritic electrical synapses between mammalian retinal ganglion cells. J. Neurosci. 24, 10553–10567 (2004).
Deans, M. R., Volgyi, B., Goodenough, D. A., Bloomfield, S. A. & Paul, D. L. Connexin36 is essential for transmission of rod-mediated visual signals in the mammalian retina. Neuron 36, 703–712 (2002).
Schubert, T. et al. Connexin36 mediates coupling of α-ganglion cells in mouse retina. J. Comp. Neurol. (in the press).
Deans, M. R. & Paul, D. L. Mouse horizontal cells do not express connexin26 or connexin36. Cell Commun. Adhes. 8, 361–366 (2001).
Dang, L. et al. Connexin 36 in photoreceptor cells: studies on transgenic rod-less and cone-less mouse retinas. Mol. Vis. 10, 323–327 (2004).
Demb, J. B. & Pugh, E. N. Connexin36 forms synapses essential for night vision. Neuron 36, 551–553 (2002).
Massey, S. C. et al. Multiple neuronal connexins in the mammalian retina. Cell Commun. Adhes. 10, 425–430 (2003).
DeVries, S. H., Qi, X., Smith, R., Makous, W. & Sterling, P. Electrical coupling between mammalian cones. Curr. Biol. 12, 1900–1907 (2002).
Laughlin, S. B. Retinal function: coupling cones clarifies vision. Curr. Biol. 12, R833–R834 (2002).
Veruki, M. L. & Hartveit, E. AII (rod) amacrine cells form a network of electrically coupled interneurons in the mammalian retina. Neuron 33, 935–946 (2002).
Hornstein, E. P., Verweij, J. & Schnapf, J. L. Electrical coupling between red and green cones in primate retina. Nature Neurosci. 7, 745–750 (2004).
Li, W. & DeVries, S. H. Separate blue and green cone networks in the mammalian retina. Nature Neurosci. 7, 751–756 (2004).
Tsukamoto, Y., Morigiwa, K., Ueda, M. & Sterling, P. Microcircuits for night vision in mouse retina. J. Neurosci. 21, 8616–8623 (2001).
Li, W., Keung, J. W. & Massey, S. C. Direct synaptic connections between rods and OFF cone bipolar cells in the rabbit retina. J. Comp. Neurol. 474, 1–12 (2004).
Kamermans, M. & Fahrenfort, I. Ephaptic interactions within a chemical synapse: hemichannel-mediated ephaptic inhibition in the retina. Curr. Opin. Neurobiol. 14, 531–541 (2004).
He, S., Weiler, R. & Vaney, D. I. Endogenous dopaminergic regulation of horizontal cell coupling in the mammalian retina. J. Comp. Neurol. 418, 33–40 (2000).
Janssen-Bienhold, U. et al. Identification and localization of connexin26 within the photoreceptor-horizontal cell synaptic complex. Vis. Neurosci. 18, 169–178 (2001).
Kamermans, M. et al. Hemichannel-mediated inhibition in the outer retina. Science 292, 1178–1180 (2001).
Pottek, M. et al. Contribution of connexin26 to electrical feedback inhibition in the turtle retina. J. Comp. Neurol. 466, 468–477 (2003).
Güldenagel, M. et al. Expression patterns of connexin genes in mouse retina. J. Comp. Neurol. 425, 193–201 (2000).
Bloomfield, S. A., Xin, D. & Osborne, T. Light-induced modulation of coupling between AII amacrine cells in the rabbit retina. Vis. Neurosci. 14 565–576 (1997).
Bloomfield, S. A. & Volgyi, B. Function and plasticity of homologous coupling between AII amacrine cells. Vision Res. 44, 3297–3306 (2004).
Veruki, M. L. & Hartveit, E. Electrical synapses mediate signal transmission in the rod pathway of the mammalian retina. J. Neurosci. 22, 10558–10566 (2002).
Mas, C. et al. Association of the connexin36 gene with juvenile myoclonic epilepsy. J. Med. Genet. 41, e93 (2004).
Krüger, O. et al. Defective vascular development in connexin 45-deficient mice. Development 127, 4179–4193 (2000).
Srinivas, M. et al. Functional properties of channels formed by the neuronal gap junction protein connexin36. J. Neurosci. 19, 9848–9855 (1999).
Moreno, A. P., Laing, J. G., Beyer, E. C. & Spray, D. C. Properties of gap junction channels formed of connexin 45 endogenously expressed in human hepatoma (SKHep1) cells. Am. J. Physiol. 268, C356–C365 (1995).
Martinez, A. D., Hayrapetyan, V., Moreno, A. P. & Beyer, E. C. A carboxyl terminal domain of connexin43 is critical for gap junction plaque formation but not for homo- or hetero-oligomerization. Cell Commun. Adhes. 10, 323–328 (2003).
Work in our laboratory was supported by grants from the German Research Association to K.W.
The authors declare no competing financial interests.
- LOW-PASS FILTER
A low-pass filter preferentially allows the transmission of low-frequency stimuli and the transfer of sub-threshold potentials that favour synchronous activity. Low-pass filter characteristics of electrical synapses are a consequence of the conductance of gap junction channels feeding into the parallel capacitance and conductance of the postsynaptic cell.
- MAUTHNER CELLS
A bilateral pair of brainstem neurons, characteristic of fish, that receive acoustic information and trigger an escape response.
- OLIVOCEREBELLAR COMPLEX
A functional unit of the inferior olive and cerebellum. Interactions between the cerebellum and inferior olive contribute to the acquisition and extinction of the eyeblink.
- LEAK CONDUCTANCE
Leak conductance in gap junctions means that these channels might allow the flow or exchange of small currents from cell to cell, therefore lowering their input resistance.
- HARMALINE TREMOR
In animals, harmaline injections trigger oscillatory activity in the inferior olive, which is accompanied by a tremor of the same frequency (4–12 Hz). This harmaline-induced tremor seems to be similar, in many aspects, to the tremor seen in patients with Parkinson's disease.
- BASKET CELLS
Inhibitory interneurons located in the molecular layer of the cerebellum. Basket cells are located close to Purkinje cells and spread out horizontally.
- STELLATE CELLS
Inhibitory interneurons located in the molecular layer of the cerebellum. Stellate cells are symmetrical in shape and their processes radiate from the cell body.
- GAMMA AND THETA OSCILLATIONS
Oscillatory activity of specific frequency bands in distinct brain regions correlates with distinct behavioural states. During awake as well as active periods and REM sleep, theta (4–12 Hz) and gamma (20–90 Hz) oscillations are prevalent and are thought to involve interneurons as well as principal cells.
- HIGH-FREQUENCY OSCILLATIONS
(HFOs). When mice or rats are immobile and awake, or in the non-REM phase of sleep, the so-called 'ripple' oscillations or high-frequency oscillations (in the range of 100–600 Hz) can be measured. Recent evidence indicates that ripples have a specific role in memory processing.
(Also known as d-spikes or fast pre-potentials). Brief low-amplitude potentials that have the appearance of action potentials but are much smaller. Spikelets are widely considered to be the electrophysiological correlate of electrotonic coupling through gap junctions.
- STRATUM ORIENS
The stratum oriens is located between the alveus and the pyramidal cell layer of the hippocampus. Besides some astrocytes and interneurons, it mainly consists of axon bundles from CA1 pyramidal cells.
- Cre/LoxP RECOMBINATION
A site-specific recombination system derived from Escherichia coli bacteriophage P1. Two short DNA sequences (loxP sites) are engineered to flank the target DNA. Activation of the Cre-recombinase enzyme catalyses recombination between the loxP sites, leading to excision of the intervening sequence.
- THALAMOCORTICAL CIRCUITRY
This distinct circuitry might underlie the capacity of the cortex to induce or maintain thalamocortical synchrony.
- THALAMIC OSCILLATIONS
During relaxed wakefulness, thalamic oscillations in the human electroencephalogram mainly consist of alpha (∼8–13 Hz) oscillations, which, with the onset of drowsiness, are briefly replaced by slower theta (∼2–7 Hz) oscillations, prior to the onset of spindle (7–14 Hz) and slow-wave (<1 Hz) oscillations during sleep.
- BIPOLAR CELLS
Bipolar cells receive information formed by the interactions of horizontal cells with cone or rod photoreceptors and convey it to the inner retina. ON (cone or rod) bipolar cells respond to increases in intensity, whereas OFF (cone and rod) bipolar cells respond to decreases in intensity.
- HORIZONTAL CELLS
Horizontal cells form a network of interconnecting retinal neurons just beneath the photoreceptors (that is, the photoreceptor cells), which is responsible for averaging visual activity over space and time, as well as controlling the gain and offset of the photoreceptor signal.
- GANGLION CELLS
Output neurons of the retina, the axons of which form the optic nerve. ON ganglion cells respond to increases in intensity, whereas OFF ganglion cells respond to decreases in intensity.
- AII AMACRINE CELLS
A subtype of retinal amacrine cell with a small dendritic field that conveys the rod signal to cone bipolar cells.
- RECEPTIVE FIELD
A dynamic area of the retina in which stimulus presentation leads to the response of a particular ganglion cell.
- EPHAPTIC TRANSMISSION
Ephaptic transmission or interaction through electrical field effects is a direct electrotonic transfer of excitation from one unit to the next. The ephapse is a site where two or more nerve cell processes (axons or dendrites) touch without forming a typical synaptic contact.
[In horizontal cells]. Hemichannels could depolarize cone pedicles and subsequently activate voltage-gated Ca2+ channels. This could lead to glutamate release, which would convey a 'feedback' response appropriate for a decrease in light-induced signals that are transmitted forward by bipolar and ganglion cells.
- RIBBON SYNAPSE
Synapses characterized by an electron-dense ribbon or bar in the presynaptic terminal. The ribbon is commonly oriented at a right angle to the membrane and sits just above an evaginated ridge. It is thought that the ribbons help to guide vesicles to the release sites. Ribbon synapses are commonly found in the retinae and cochlea of vertebrates.
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Söhl, G., Maxeiner, S. & Willecke, K. Expression and functions of neuronal gap junctions. Nat Rev Neurosci 6, 191–200 (2005). https://doi.org/10.1038/nrn1627
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