Lecture 30: Neurotransmission

Question 1

Astrocyte role?

Answer 1

Play important role in physiological brain function beyond support

• release and take up neurotranmitters (eg. Glutamate)
• Express receptors (eg. NMDA)
• regulate synaptic transmission
• play important roles in brain pathology - form scars and impede axonal regrowth

Question 2

Types of astrocytes in human cortex?

Answer 2

Protoplasmic

interlaminar astrocytes

Fibrous astrocytes

Polarized astrocytes

Question 3

Protoplasmic astrocytes features, function and location?

Answer 3

• Most common type of astrocyte located in the cortex layers 2-6
• Their GFAP-positive processes do not overlap
• The domain of one astrocyte might cover 10 nerve cell bodies, many synapses (thousands to millions) and 5 blood vessels.
• They are hence important for coordination (eg to regulate blood flow in response to increased synaptic transmission)

Question 4

Fibrous astrocyte features, function and location?

Answer 4

• Found in the white and gray matter
• Their processes intermingle (ie. don’t form a domain structure)
• Probably they serve a support role for neurons (rather than information processing) and also respond to brain injury.

Question 5

Microglia function, features?

Answer 5

• Surveyors of the brains micro-environment-resident macrophages
• Mediate the brain immune response
• Phagocytose debris
• may modulate neurotransmission
• help sculpt the brain during development and may modulate synaptic transmission.

Question 6

Brain endothelial cells and pericytes: function, features, location?

Answer 6

• Pericytes encase endothelial cells in brain capillaries. They induce and maintain the BBB
• Damage to these allows the BBB to be crossed in diseases like alzheimer’s or injury like stroke.

Question 7

Neuromodulators are?

Answer 7

Chemicals that can produce slower and post-synaptic responses. Released by nerve cells and astrocytes (eg adenosine)

Question 8

Neurotrophic factors are?

Answer 8

• Released by non-neuronal cells (astrocytes, microglia) and neurons and work over long time-scales.
• Act on tyrosine-kinase type receptors to mediate growth, morphology, functional properties, survival promoting effects in the nervous system

Question 9

Fast acting vs slow acting neurotransmitter site of action?

Answer 9

Fast acting: work via ion channels (eg. glycine, GABA, glutamate)

Slow acting: work via G-protein coupled receptors (eg. dopmine, neuropeptides, GABA, acetylcholine)

Neurotransmitters can have both FAST and SLOW action depending upon the receptor sub-type they act on.