Abstract:Gap junctions mediate metabolic and electrical interactions between some cells of the central nervous system. For many types of neurons, gap junction-mediated electrical coupling is most prevalent during early development, then decreases sharply with maturation. However, neurons in the thalamic reticular nucleus (TRN), which exert powerful inhibitory control over thalamic relay cells, are electrically coupled in relatively mature animals. It is not known whether TRN cells or any neurons that are electrically c… Show more
“…We used the Pvalb-cre driver and the Rosa26-ChR2(H134R)-EYFP reporter (Ai32; Madisen et al, 2012) to express ChR2 in TRN neurons. Patch-clamp recordings were performed in acute slices obtained from Pvalb-cre;Ai32 (PV-ChR2) mice at age P15-P20.…”
Section: Resultsmentioning
confidence: 99%
“…Situated in the path of axons connecting the thalamus and the cortex, the TRN receives excitatory inputs from collaterals of thalamocortical and corticothalamic axons and provides the major inhibitory input to thalamocortical neurons (Guillery and Harting, 2003;Pinault, 2004). Because of its location and connectivity, the TRN is often regarded as the gatekeeper of information transfer from the thalamus to the cortex and has been implicated in sensory detection, attention, and arousal (Crick, 1984;Steriade et al, 1993;McCormick and Bal, 1997;Zikopoulos and Barbas, 2006;McAlonan et al, 2008;Halassa et al, 2014;Lewis et al, 2015). Dysfunction of the TRN is associated with epilepsy (Huguenard and McCormick, 2007) and schizophrenia (Ferrarelli and Tononi, 2011).…”
It is generally thought that neurons in the thalamic reticular nucleus (TRN) form GABAergic synapses with other TRN neurons and that these interconnections are important for the function of the TRN. However, the existence of such intrinsic connections is controversial. We combine two complementary approaches to examine intrinsic GABAergic connections in the TRN of the mouse. We find that optogenetic stimulation of TRN neurons and their axons evokes GABAergic IPSCs in TRN neurons in mice younger than 2 weeks of age but fails to do so after that age. Blocking synaptic release from TRN neurons through conditional deletion of vesicular GABA transporter has no effect on spontaneous IPSCs recorded in TRN neurons aged 2 weeks or older while dramatically reducing GABAergic transmission in thalamic relay neurons. These results demonstrate that except for a short period after birth, the TRN of the mouse lacks intrinsic GABAergic connections.
“…We used the Pvalb-cre driver and the Rosa26-ChR2(H134R)-EYFP reporter (Ai32; Madisen et al, 2012) to express ChR2 in TRN neurons. Patch-clamp recordings were performed in acute slices obtained from Pvalb-cre;Ai32 (PV-ChR2) mice at age P15-P20.…”
Section: Resultsmentioning
confidence: 99%
“…Situated in the path of axons connecting the thalamus and the cortex, the TRN receives excitatory inputs from collaterals of thalamocortical and corticothalamic axons and provides the major inhibitory input to thalamocortical neurons (Guillery and Harting, 2003;Pinault, 2004). Because of its location and connectivity, the TRN is often regarded as the gatekeeper of information transfer from the thalamus to the cortex and has been implicated in sensory detection, attention, and arousal (Crick, 1984;Steriade et al, 1993;McCormick and Bal, 1997;Zikopoulos and Barbas, 2006;McAlonan et al, 2008;Halassa et al, 2014;Lewis et al, 2015). Dysfunction of the TRN is associated with epilepsy (Huguenard and McCormick, 2007) and schizophrenia (Ferrarelli and Tononi, 2011).…”
It is generally thought that neurons in the thalamic reticular nucleus (TRN) form GABAergic synapses with other TRN neurons and that these interconnections are important for the function of the TRN. However, the existence of such intrinsic connections is controversial. We combine two complementary approaches to examine intrinsic GABAergic connections in the TRN of the mouse. We find that optogenetic stimulation of TRN neurons and their axons evokes GABAergic IPSCs in TRN neurons in mice younger than 2 weeks of age but fails to do so after that age. Blocking synaptic release from TRN neurons through conditional deletion of vesicular GABA transporter has no effect on spontaneous IPSCs recorded in TRN neurons aged 2 weeks or older while dramatically reducing GABAergic transmission in thalamic relay neurons. These results demonstrate that except for a short period after birth, the TRN of the mouse lacks intrinsic GABAergic connections.
“…Estimates of the conductance of gap junctional channels coupling IO neurons (G j ) were calculated following Bennett (1966) and Parker et al (2009):…”
Gap junctions constitute the only form of synaptic communication between neurons in the inferior olive (IO), which gives rise to the climbing fibers innervating the cerebellar cortex. Although its exact functional role remains undetermined, electrical coupling was shown to be necessary for the transient formation of functional compartments of IO neurons and to underlie the precise timing of climbing fibers required for cerebellar learning. So far, most functional considerations assume the existence of a network of permanently and homogeneously coupled IO neurons. Contrasting this notion, our results indicate that coupling within the IO is highly variable. By combining tracer-coupling analysis and paired electrophysiological recordings, we found that individual IO neurons could be coupled to a highly variable number of neighboring neurons. Furthermore, a given neuron could be coupled at remarkably different strengths with each of its partners. Freeze-fracture analysis of IO glomeruli revealed the close proximity of glutamatergic postsynaptic densities to connexin 36-containing gap junctions, at distances comparable to separations between chemical transmitting domains and gap junctions in goldfish mixed contacts, where electrical coupling was shown to be modulated by the activity of glutamatergic synapses. On the basis of structural and molecular similarities with goldfish mixed synapses, we speculate that, rather than being hardwired, variations in coupling could result from glomerulus-specific long-term modulation of gap junctions. This striking heterogeneity of coupling might act to finely influence the synchronization of IO neurons, adding an unexpected degree of complexity to olivary networks.
“…Note: PC, pyramidal cell; FS, fast-spiking interneuron; LTS, low-threshold spiking interneuron; TRN, thalamic reticular nucleus; VBN, ventrobasal nucleus; n.d., not determined.As determined electrical connectivity rates depend on the distance between the 2 tested cells, we have also specified, where known, the range used by the authors for testing connectivity. a Yu et al 2012 (10s of μm). b Wang et al 2010 (0–20 μm). c Pangratz-Fuehrer and Hestrin 2011 d Gibson et al 1999 (<50 μm). e Meyer et al 2002 (<100 μm). f Parker et al 2009 (≤2 μm). g Long et al 2004 (<5 μm). h Blethyn et al 2008. i Lee et al 2010 (<5 μm).…”
Section: Principles Of Gap Junction Signalingmentioning
confidence: 99%
“…Figure 2.Plasticity of coupling strength as a consequence of development and electrical activity. ( A ) From the first postnatal week ( Aa ) to the second ( Ab ), there is an 8-fold increase in g j (junctional conductance), possibly as a consequence of a decrease in the R i (input resistance) of a similar magnitude (Parker et al 2009). ( B ) After 2 TRN neurons are simultaneously active for a number of times ( Ba , upper cell pair), the electrical connection between them decreases in strength, symmetrically ( Bb , upper cell pair); when only one cell in the pair is active ( Ba , lower cell pair), the electrical connection also decreases in strength, but in an asymmetric way, the formerly active cell being able to receive less input than it can send to the other cell ( Bb , lower cell pair; Haas et al 2011).…”
Section: Principles Of Gap Junction Signalingmentioning
The presence of direct, cytoplasmatic, communication between neurons in the brain of vertebrates has been demonstrated a long time ago. These gap junctions have been characterized in many brain areas in terms of subunit composition, biophysical properties, neuronal connectivity patterns, and developmental regulation. Although interesting findings emerged, showing that different subunits are specifically regulated during development, or that excitatory and inhibitory neuronal networks exhibit various electrical connectivity patterns, gap junctions did not receive much further interest. Originally, it was believed that gap junctions represent simple passageways for electrical and biochemical coordination early in development. Today, we know that gap junction connectivity is tightly regulated, following independent developmental patterns for excitatory and inhibitory networks. Electrical connections are important for many specific functions of neurons, and are, for example, required for the development of neuronal stimulus tuning in the visual system. Here, we integrate the available data on neuronal connectivity and gap junction properties, as well as the most recent findings concerning the functional implications of electrical connections in the developing thalamus and neocortex.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
