6.3 Inactivation gates

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En provenance du cours de Peking University

Advanced Neurobiology I

258 notes

Peking University

Advanced Neurobiology I

258 notes

Hello everyone! Welcome to advanced neurobiology! Neuroscience is a wonderful branch of science on how our brain perceives the external world, how our brain thinks, how our brain responds to the outside of the world, and how during disease or aging the neuronal connections deteriorate. We’re trying to understand the molecular, cellular nature and the circuitry arrangement of how nervous system works. Through this course, you'll have a comprehensive understanding of basic neuroanatomy, electral signal transduction, movement and several diseases in the nervous system. This advanced neurobiology course is composed of 2 parts (Advanced neurobiology I and Advanced neurobiology II, and the latter will be online later). They are related to each other on the content but separate on scoring and certification, so you can choose either or both. It’s recommended that you take them sequentially and it’s great if you’ve already acquired a basic understanding of biology. Thank you for joining us!

À partir de la leçon

Ion channels, membrane potential and synaptic transmission

Let's continue with the ion channels, membrane potential and synaptic transmission.

6.1 Voltage sensing15:39

6.2 The Na+ gating current8:04

6.3 Inactivation gates17:37

6.4 Ion channel, membrane potential and synaptic transmission I15:12

6.5 Ion channel, membrane potential and synaptic transmission II7:30

6.6 Ion channel, membrane potential and synaptic transmission III12:53

6.7 Ion channel, membrane potential and synaptic transmission IV7:01

6.8 Ion channel, membrane potential and synaptic transmission V9:44

Rencontrer les enseignants

Yan Zhang
Professor
School of Life Sciences, Peking University
Yulong Li
Research Fellow
School of Life Sciences, Peking University

How do you block calcium influx?

How do you block calcium influx?

I know >> I think we can

>> Calcium channels [INAUDIBLE].

>> Okay, that is one possibility.

That is to block the calcium channel.

How do you block a calcium channel?

>> We will have some

protein or [INAUDIBLE] >> Right.

So you say, well,

it's none of business, some other people will find out this radius.

Help me block this calcium channel.

Well yes, there are certain drugs that can selectively block the specific calcium

channel.

One simple one is Ketamine, okay you could use Ketamine.

There is also tryvaline and

structurally similar to calcium, but the sizes are so different.

So it turns out that once it gets into the calcium channel, it would just block

the pore of calcium channel, no longer allow the calcium to come in.

Okay?

So ketamine can be used.

And then later people actually found more

specific peptide toxins from spider,

from scorpion, from snake,

from snail, from all those.

Since right?

>> [LAUGH] >> That has those toxins,

those peptide toxins that can selectively block one

with the other sub-type.

Of voltage-gated calcium channel.

So ketamine will block all of the voltage-gated calcium channel,

as long as they have a pore.

The pore looks the same.

THey all allow calcium to come in.

So ketamine can block, okay?

And those peptide toxins are more specific.

They can even recognize the subtype.

Okay, has a high affinity.

So that's the reason during evolution some of the smells,

the smell from the sea, they actually eat fish, okay.

How do they eat fish?

It looks they move slow, right?

But it actually has no specific toxin.

Whenever they get closer to the fish, they just immediately bite the fish and

inject the toxin.

And this fish will paralyze, because they are calcium channel.

Of the snails, they will paralyze.

The injected toxin will paralyze the fish.

Once you're getting calcium channel and you know, the also

rely on synapse transmission to move their muscles to run away.

Okay?

So, whenever there's no function of their calcium channels,

there's no transmitter release.

The fissure will get paralyzed, okay, and then the snail,

even though it moves slowly, the fish is a paralyzed fish,

so it can still take its time to enjoy is a good fish, right?

Okay. And so and

it turns out that's just a little bit more.

It turns out toxin for example,

from snail, can inhibit what did you get in calcium channel.

Turns out some of them actually are good drugs for our humans.

So it turns out that some of the calcium channel for

fish is to mediate a transmitter release and the muscle contraction.

But for humans,

humans use another type to control muscle contraction and transmitter release.

The corresponding path the type from fish in human

is present in some neuron in the central nervous system, okay?

And the people find actually If you inhibit those

calcium channel in the central nervous,

it can help you to eliminate or reduce headache or

some this called intractable pain, OK?

Meaning somehow you just feel pain and you don't know where it comes from.

That is why it's called intractable pain OK?

And it turns out some of those blockers are peptide toxins from snails.

And then, when people it eat and then still, nobody know how does it work.

You only know it works somewhere in the central brain.

Okay.

Then you don't have that pain.

Okay.

So this has been FDA approved.

Okay.

So, this is one of the examples that starting some of the fundamentals of

synapse transmission could benefit human health.

Although, probably Those heroes did not think about that they're identification or

they're characterization could lead to such application.

So what will be the other way to block the influx of calcium?

You can block from outside by blocking the calcium channel using

the ketamine or toxin.

But you can also do it from inside.

How do you do it? How do you do it?

Inject some calcium into the cell.

>> Inject some calcium, okay.

This is good.

So if you are injecting calcium, you don't rely on the voltage-gated calcium channel.

Your prediction will be,

if you're purely injecting calcium, that can trigger transmitter release, isn't it?

Right, because if calcium is really essential,

the opening of the voltage-gated calcium channel,

the purpose is just to deliver calcium inside, right?

So we directly inject calcium.

And alternatively, we can also block the influx of calcium from inside.

How do we do it?

Well, it's easy.

We have this that can chelate calcium.

And last time we just applied outside, and this time, we leave the outside intact.

We just inject the which will chelate calcium inside.

So, even though the voltage gated calcium channel might be opening,

unless some calcium comes in But you have this, a lot of keylater,

just inside, near the of the calcium channel.

Once it comes in, grab it.

Comes in, grab it.

So we are essentially buffering and keylating those calcium.

And then doing that experiment can also

demonstrating that you don't alter the external calcium.

You just intracellularly buffer, or chelate, the calcium.

And then in that condition, if the transmitter release is gone,

this will also prove that calcium

influx is of functional importance, rather than it's a epiphenomenon.

Okay?

So we start the experiment, calcium imaging or

calcium current measurements that you demonstrate.

There's indeed influx.

And then you can block it, either through the channel blockers or intercellularly.

Then you eliminate this effect.

And then you can inject calcium.

And it's demonstrating that injecting calcium by your patch

if that is sufficient to trigger a transmitted release,

then this demonstrates sufficiency.

So taking all these parameters together,

you have the necessary and efficiency parameters.

Together, demonstrating the essential roles of calcium influx in transmitted.

Okay?

So, with that, we conclude our section, and then for our next class,

we are still going to discuss a little bit about the voltage gated calcium channel.

And it's regulation.

And then, we are also going to discuss, in more detail,

how do we identify the of calcium, as well as those

important protein machinery that mediate a transmitter release.

Okay, and, again, our scenario will be you guys time travel back.

Maybe 30 years ago or 40 years ago, rather than 50 or 70 years ago.

And how were you using you, using your modern technology,

and tools that you carry to identify the potential or essential machineries?

Molecular mercenaries that mediate the sensing of calcium.

Calcium has to activate something and mediate to the direct fusion of

the synaptic to the plasma membrane.

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