Lecture 21: Neurotransmission

Question 1

What are the types of cells in the brain?

Answer 1

Neurons
Astrocytes
Microglia
Glia (General)
Endothelial cells and pericytes

Question 2

What is the function of astrocytes?

Answer 2

• Support; Release and take up neurotransmitter i.e glutamate
• Express receptors i.e NMDA
• Regulate synaptic transmission
• Conduct electrical events via gap junctions
• MEMORY FORMATION?
• Neurotrophin production and release
• May gen new neurons…..

Question 3

Do astrocytes play a role in disease?

Answer 3

• Important role in brain pathology;

- Scars, immune activation etc

Question 4

Is there more than one type of astrocyte? if so what?

Answer 4

Yes, four different types;

• Protoplasmic
• Fibrous

(general knowledge)
- Interlaminar and polarized astrocytes

Question 5

Describe the organisation of protoplasmic astrocytes in the cortex:

Answer 5

• Most common type
• Laters 2-6 of cortex
• Domain organisation, which might cover ten nerve cell bodies, many synapses and five blood vessels.

i.e imp. coordination position.

Question 6

What sort of function would protoplasmic astrocytes have if they are in a coordination position?

Answer 6

• Regulate blood flow in response to increased synaptic transmission.

Question 7

What are fibrous astrocytes?

Answer 7

• Grey and white matter located
• Their processes intermingle i.e no domain structures
• Probably sere a support role for neurons and respond to brain injury.

Question 8

What is gliotransmisison // glioneuronal functional units?

Answer 8

The release of transmitters from astrocytes that act on neurons

Possibly this is how memories are encoded, speculation this is the underpinning of the complexity of the human brain

Question 9

What are microglia?

Answer 9

• Surveyors of the brains microenvironment, very sensitive to brain perturbations.

= Resident macrophages of the brain, thus phagocytose debris etc

• May modulate neurotranmission
• Help sculpt the brain during development

Question 10

What is the role of brain endothelial cells and pericytes?

Answer 10

• Pericytes encase endothelial cells in brain capillaries and maintain the BBB
• In many neurological disorders it is thought the BBB is compromised

Question 11

How is transmitter action terminated?

Answer 11

Termination of transmitter action is achieved by either metabolism and/or re-uptake into neurons and/or glial cells (astrocytes) by specific transporter proteins

Question 12

How do most drugs act on the CNS?

Answer 12

Most drugs that act on the brain and spinal coed do so by interacting in some way with chemical neurotransmission, or with modulators of transmission i.e astrocytes or microglia

Question 13

Given the complexity of the brain, what else does the function of drugs depend on?

Answer 13

• Depends on which neurotransmitter system it modulates or mimics
• Anatomical localisation of the neurotransmitter system

(Chemical neuroanatomy)

Question 14

What are some neurotransmitters?

Answer 14

• Monoamiens; Dopamine, serotonin, norepinephrine
• AA/ AA derivatives; GABA, Glutamate, Glycine
• ACh
• Neuropeptides (neuromodulators and co-transmitters)

Question 15

How do neuromodulators work?

Answer 15

Produce slower pre and post synaptic responses. Released by nerve cells and astrocytes i.e adenosine

Question 16

What are neurotrophic factors?

Answer 16

• Released by glial and neuronal cells
• Act over long time scales
• Act specifically on tyrosine kinase type receptor to mediate growth, morphology, functional properties, survival promoting effects in the nervous system (i.e nerve growth factor, BDNF, IGF-1)

Question 17

What are the fast acting neurotransmitters?

Answer 17

Fast acting; Work via ion channels i.e glycine, GABA, glutamate

Question 18

What are slow acting neurotransmitters?

Answer 18

Slow acting via g protein coupled receptors i.e dopamine, neuropeptides, GABA, ACh