Neuroscience

1. Neurotransmitter
receptors
DOMINA PETRIC, MD

2. Ionotropic receptors
I.

3. Nicotinic acetylcholine receptor
It is occupied and activated by
nicotine in smokers.
Channel opening is gated by the
binding of the neurotransmitter to
its receptor.

4. Glutamate ionotropic receptors
Glutamate
AMPA
NMDA
Kainate

5. NMDA receptors
Both glutamate and glycine have to interact
with the receptor to open the channel.
Magnesium ions can aggregate in the deep
binding site of the NMDA receptor.
When the magnesium is bind there is no
conductance.

6. GABA receptors
There are places on the GABA receptors for:
 picrotoxin
 benzodiazepines
 barbiturates
 steroids
Chloride ions pass through the channel from the
inside to outside typically in mature neurons.

7. http://michaeldmann.net
Ionotropic receptor

8. Calcium is critical for mediating
synaptic plasticity.
http://www.interactive-biology.com

9. Metabotropic receptors
II.

10. G-protein coupled receptor
 Receptor is a monomeric integral membrane protein.
 It is associated with G proteins on its cytoplasmic
surface.
 When the neurotransmitter binds to the receptor, G
proteins become activated.
 G proteins interact with effector proteins.
 Effector proteins produce variety of intercellular
messengers and those messengers can gate some ion
channels.

11. G-protein coupled receptor
Receptor
Neurotransmitter binds
G protein is activated and
interacts with effector protein.
Effector
protein
produces
intercellular
messengers
Intercellular
messengers
gate ion
channel
Amplification of the signal

12. G-protein coupled receptor
 There can be amplification of the signal as these
metabolic steps are occuring.
 G-protein coupled receptors can also interact with
transcription factors that can modify gene expression.
 CREB binding domene in our genes is the regulatory
element which can be activated with G-protein cuopled
receptors.
 Transduction of photons into electrical energy requires
the activation of G-protein coupled receptor system.

13. Synaptic integration
III.

14. Synapse
 Action potential invades the end of an axon (presynaptic
terminal).
 Wave of depolarisation conveys positive charge along the
length of presynaptic terminal.
 When depolarisation reaches voltage gated calcium
channels, channels open and there is influx of calcium.
 Calcium is the key trigger that leads to the fusion of
docked vesicles.
 Neurotransmitter in docked and now fused vesicles
passively diffuse out into the synaptic cleft.

15. Excitatory postsynaptic potential
The reversal potential of
the active conductance is
above the threshold for
firing an action potential.

16. Inhibitory postsynaptic potential
For example if there is
activation of GABA
synapse, there will be
hyperpolarisation due
to chloride ions influx.

17. Excitatory activity of GABA in
developing brain
In the immature neuron there is more chloride ions inside of
the cell than in mature neuron because of:
 Na+/K+/2 Cl- transporter (all ions go inside the cell) that
will be replaced with K+/Cl- transporter (both ions go out
of the cell) in mature neuron.
So in the immature neuron there is high concentration of
chloride ions INSIDE the cell and low concentration of
chloride ions in the extracellular space.
 In immature neuron GABA is excitatory neurotransmitter.
 In mature neuron GABA is inhibitory neurotransmitter.

18. Another book association
(Domina Petric, MD)
Immature neuron Mature neuron
Immature neuron is like closed
book with chloride ions inside
the book (inside the cell).
When the child is born, ˝the book˝
opens and chloride ions escape
from the cell to the exctracellular
space because of the new
transporter that throws out
of the cell chloride ions.
GABA is excitatory neurotransmitter. GABA is inhibitory neurotransmitter.
When the channel opens, chloride ions When the channel opens there will be
go out of the cell and there is influx of chloride ions from extracellular space
depolarisation. into the cell (hyperpolarisation).

19. Synapse integration
No one synapse is strong enough to result in
the generation of an action potential in the
postsynaptic neuron.
There must be many synapses, many
excitatory inputs converging on the same
neuron at the same time in order to depolarize
that membrane sufficiently to reach treshold.

20. Literature
https://www.coursera.org/learn/me
dical-neuroscience/lecture:
Leonard E. White, PhD, Duke
University
http://michaeldmann.net
http://www.interactive-biology.com