Discussion Paper 9

Question 1

What are the 6 behaviours that mammals display upon infection?

Answer 1

1. Social withdrawal
2. Increased pain sensitivity
3. Lethargy
4. Warmth-seeking
5. Appetite loss
6. Fever

Question 2

What is the purpose of sick behaviours?

Answer 2

To eliminate pathogens and increase survival rates

Question 3

What is LPS?

Answer 3

Lipopolysaccharide: a component of the membrane of gram-negative bacteria

Question 4

What are the 2 ways that the researchers mimicked sickness in mice? Why did they only use LPS?

Answer 4

LPS and polyinosinic:polycytidylic acid

Use only LPS because there was no difference between the mice infected with either “sick” inducing substance - stuck with LPS for consistency

Question 5

What is cFos and why was it used as a marker of cell activity?

Answer 5

Ubiquitous molecule which indicates activity of the cell: cFos+ indicates the neurons are active

Question 6

Why did the researchers focus in on the VMPO for this study?

Answer 6

It is located near the circumventricular organ (which lines the ventricles of the brain, this area has a leaky BBB and therefore would be exposed to cytokines etc. - also had connections to areas which control sick behaviours)

Question 7

The hypothalamus is known to regulate this parameter affected in sickness

Answer 7

Temperature regulation

Question 8

What is MERFISH and why was it used in this experiment?

Answer 8

Fancy form of in situ hybridization, used to visualize the VMPO neurons

Question 9

Do VMPO neurons express cytokine receptors? What 2 techniques were used to confirm this?

Answer 9

Yes

RNA-sequencing and MERFISH

Question 10

According to the Ephys experiments, are cytokines able to activate VMPO neurons?

Answer 10

Yes

Question 11

What is the significance of the median preoptic region (MnPO) and the arcuate nucleus (ARc)?

Answer 11

These are regions that the VMPO neurons project to

Question 12

In the channelrhodopsin experiments, activation of the neurons projecting from the VMPO to the Arcuate nucleus resulted in…

Answer 12

Decreased food consumption

Question 13

In the channelrhodopsin experiments, activation of the neurons projecting from the VMPO to the median preoptic nucleus resulted in…

Answer 13

Increased body temperature

Question 14

What are some limitations to this study?

Answer 14

There were many other neurons which were activated in response to LPS and other regions of the brain which were not investigated: this is likely not the full picture as to what is going on in sickness