JoVE Visualize What is visualize?
Stop Reading. Start Watching.
Advanced Search
Stop Reading. Start Watching.
Regular Search
Find video protocols related to scientific articles indexed in Pubmed.
The recurrent case for the Renshaw cell.
J. Neurosci.
PUBLISHED: 09-19-2014
Show Abstract
Hide Abstract
Although Renshaw cells (RCs) were discovered over half a century ago, their precise role in recurrent inhibition and ability to modulate motoneuron excitability have yet to be established. Indirect measurements of recurrent inhibition have suggested only a weak modulatory effect but are limited by the lack of observed motoneuron responses to inputs from single RCs. Here we present dual recordings between connected RC-motoneuron pairs, performed on mouse spinal cord. Motoneuron responses demonstrated that Renshaw synapses elicit large inhibitory conductances and show short-term potentiation. Anatomical reconstruction, combined with a novel method of quantal analysis, showed that the strong inhibitory input from RCs results from the large number of synaptic contacts that they make onto individual motoneurons. We used the NEURON simulation environment to construct realistic electrotonic models, which showed that inhibitory conductances from Renshaw inputs exert considerable shunting effects in motoneurons and reduce the frequency of spikes generated by excitatory inputs. This was confirmed experimentally by showing that excitation of a single RC or selective activation of the recurrent inhibitory pathway to generate equivalent inhibitory conductances both suppress motoneuron firing. We conclude that recurrent inhibition is remarkably effective, in that a single action potential from one RC is sufficient to silence a motoneuron. Although our results may differ from previous indirect observations, they underline a need for a reevaluation of the role that RCs perform in one of the first neuronal circuits to be discovered.
Related JoVE Video
Energetics of shuttle runs: the effects of distance and change of direction.
Int J Sports Physiol Perform
PUBLISHED: 04-03-2014
Show Abstract
Hide Abstract
Shuttle runs can be used to study the physiological responses in sports (such as basketball) characterized by sprints (accelerations/ decelerations) and changes of direction.
Related JoVE Video
Chloride ions in the pore of glycine and GABA channels shape the time course and voltage dependence of agonist currents.
J. Neurosci.
PUBLISHED: 10-07-2011
Show Abstract
Hide Abstract
In the vertebrate CNS, fast synaptic inhibition is mediated by GABA and glycine receptors. We recently reported that the time course of these synaptic currents is slower when intracellular chloride is high. Here we extend these findings to measure the effects of both extracellular and intracellular chloride on the deactivation of glycine and GABA currents at both negative and positive holding potentials. Currents were elicited by fast agonist application to outside-out patches from HEK-293 cells expressing rat glycine or GABA receptors. The slowing effect of high extracellular chloride on current decay was detectable only in low intracellular chloride (4 mm). Our main finding is that glycine and GABA receptors "sense" chloride concentrations because of interactions between the M2 pore-lining domain and the permeating ions. This hypothesis is supported by the observation that the sensitivity of channel gating to intracellular chloride is abolished if the channel is engineered to become cation selective or if positive charges in the external pore vestibule are eliminated by mutagenesis. The appropriate interaction between permeating ions and channel pore is also necessary to maintain the channel voltage sensitivity of gating, which prolongs current decay at depolarized potentials. Voltage dependence is abolished by the same mutations that suppress the effect of intracellular chloride and also by replacing chloride with another permeant ion, thiocyanate. These observations suggest that permeant chloride affects gating by a foot-in-the-door effect, binding to a channel site with asymmetrical access from the intracellular and extracellular sides of the membrane.
Related JoVE Video
Human ?3?4 neuronal nicotinic receptors show different stoichiometry if they are expressed in Xenopus oocytes or mammalian HEK293 cells.
PLoS ONE
PUBLISHED: 04-13-2010
Show Abstract
Hide Abstract
The neuronal nicotinic receptors that mediate excitatory transmission in autonomic ganglia are thought to be formed mainly by the ?3 and ?4 subunits. Expressing this composition in oocytes fails to reproduce the properties of ganglionic receptors, which may also incorporate the ?5 and/or ?2 subunits. We compared the properties of human ?3?4 neuronal nicotinic receptors expressed in Human embryonic kidney cells (HEK293) and in Xenopus oocytes, to examine the effect of the expression system and ?:? subunit ratio.
Related JoVE Video
Intracellular chloride ions regulate the time course of GABA-mediated inhibitory synaptic transmission.
J. Neurosci.
PUBLISHED: 08-21-2009
Show Abstract
Hide Abstract
The time-dependent integration of excitatory and inhibitory synaptic currents is an important process for shaping the input-output profiles of individual excitable cells, and therefore the activity of neuronal networks. Here, we show that the decay time course of GABAergic inhibitory synaptic currents is considerably faster when recorded with physiological internal Cl(-) concentrations than with symmetrical Cl(-) solutions. This effect of intracellular Cl(-) is due to a direct modulation of the GABA(A) receptor that is independent of the net direction of current flow through the ion channel. As a consequence, the time window during which GABAergic inhibition can counteract coincident excitatory inputs is much shorter, under physiological conditions, than that previously measured using high internal Cl(-). This is expected to have implications for neuronal network excitability and neurodevelopment, and for our understanding of pathological conditions, such as epilepsy and chronic pain, where intracellular Cl(-) concentrations can be altered.
Related JoVE Video
Determining the neurotransmitter concentration profile at active synapses.
Mol. Neurobiol.
PUBLISHED: 07-06-2009
Show Abstract
Hide Abstract
Establishing the temporal and concentration profiles of neurotransmitters during synaptic release is an essential step towards understanding the basic properties of inter-neuronal communication in the central nervous system. A variety of ingenious attempts has been made to gain insights into this process, but the general inaccessibility of central synapses, intrinsic limitations of the techniques used, and natural variety of different synaptic environments have hindered a comprehensive description of this fundamental phenomenon. Here, we describe a number of experimental and theoretical findings that has been instrumental for advancing our knowledge of various features of neurotransmitter release, as well as newly developed tools that could overcome some limits of traditional pharmacological approaches and bring new impetus to the description of the complex mechanisms of synaptic transmission.
Related JoVE Video
Optical measurement of mGluR1 conformational changes reveals fast activation, slow deactivation, and sensitization.
Proc. Natl. Acad. Sci. U.S.A.
PUBLISHED: 06-22-2009
Show Abstract
Hide Abstract
Metabotropic glutamate receptor (mGluR) activation has been extensively studied under steady-state conditions. However, at central synapses, mGluRs are exposed to brief submillisecond glutamate transients and may not reach steady-state. The lack of information on the kinetics of mGluR activation impairs accurate predictions of their operation during synaptic transmission. Here, we report experiments designed to investigate mGluR kinetics in real-time. We inserted either CFP or YFP into the second intracellular loop of mGluR1beta. When these constructs were coexpressed in PC12 cells, glutamate application induced a conformational change that could be monitored, using fluorescence resonance energy transfer (FRET), with an EC(50) of 7.5 microM. The FRET response was mimicked by the agonist DHPG, abolished by the competitive antagonist MCPG, and partially inhibited by mGluR1-selective allosteric modulators. These results suggest that the FRET response reports active conformations of mGluR1 dimers. The solution exchange at the cell membrane was optimized for voltage-clamped cells by recording the current induced by co-application of 30 mM potassium. When glutamate was applied at increasing concentrations up to 2 mM, the activation time course decreased to a minimum of approximately 10 ms, whereas the deactivation time course remained constant (approximately 50 ms). During long-lasting applications, no desensitization was observed. In contrast, we observed a robust sensitization of the FRET response that developed over approximately 400 ms. Activation, deactivation, and sensitization time courses and amplitudes were used to derive a kinetic scheme and rate constants, from which we inferred the EC(50) and frequency dependence of mGluR1 activation under non-steady-state conditions, as occurs during synaptic transmission.
Related JoVE Video

What is Visualize?

JoVE Visualize is a tool created to match the last 5 years of PubMed publications to methods in JoVE's video library.

How does it work?

We use abstracts found on PubMed and match them to JoVE videos to create a list of 10 to 30 related methods videos.

Video X seems to be unrelated to Abstract Y...

In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.