Why do people feel blue during winter?

Long time ago, one of our members wrote a blog about this. It's called seasonal depression and it has to do with sunlight and serotonin levels. Have a read:

https://biology-forums.com/index.php?article=1025

Any follow up questions, let us know!

I would like to know on any new articles about following issues since 2014.

"how (SAD - seasonal affective disorder) can be affected by light levels"

Conclude : More Sunlight product More SAD , which have less access to serotonin, the brain signalling compound associated with feelings of wellbeing and happiness

Do you have any suggestions on how SAD works under light levels?
Thank you very much for any suggestions (^v^)

Found some great articles for you:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4673349/
https://www.europeanreview.org/article/1251

From the first of 2 links above, it states:

Could you please check on whether the highlight area is correct or not?

Do you have any suggestions?
Thank you very much for any suggestions (^v^)

Here's what I think is happening. SERT is a type of transporter protein that transports serotonin from the synaptic cleft back to the presynaptic neuron.

See the illustration I drew.

Therefore, your highlighted suggestion is wrong

SERT is a protein if it assists with serotonin transport, then  higher SERT levels would lead to higher lower serotonin activity, "SERT is assisting role" Would it make more sense? if not, I would like to know why SERT would lower serotonin activity as an assisting role.

Do you have any suggestions?
Thank you very much for any suggestions (^v^)

No, SERT is a serotonin reUPTAKE protein. So:

The less sunlight → the more SERT → the less serotonin reaching the postsynaptic neuron ∴ depression.

Referring to following video, I would like to know on whether following process is correct or not.

1) When a serotonergic neuron is stimulated, serotonin is released into the synaptic cleft, this process does not require protein as mentioned on video
2) if SERT is uptaking protein, then
3) there is less serotonin-transporter generated with less protein
4) it is less likely able to remove of serotonin from the synaptic cleft back to nerve terminal
5) serotonin should remain longer within synaptic cleft, which should be more serotonin with synaptic space.

Do you have any suggestions on which processing stage is wrong?
Thank you very much for any suggestions (^v^)

(2) doesn't make sense to me.

The less SERT, the longer serotonin stays in the cleft and the more likely it is to activate serotonin receptors. Thus, the longer its effects.

SERT is the bad guy

Referring to following image, when SERT increase, I would like to know on which stage is initially affected on serotonin-transporter during serotonin synthesis



Do you have any suggestions?
Thank you very much for any suggestions (^v^)

SERT production and serotonin synthesis are not coupled. None of the steps shown above indicate the formation of SERT, as SERT levels are assumed to be normal in the video. Also, SERT is already found on the presynaptic membrane, regardless if you have SAD symptoms or not

If there is more SERT on uptaking proteins within (presynaptic membrane) nerve terminal on stage 1, then less serotonergic neuron is stimulated and less serotonin is released into the synaptic cleft, would it be correct process by the role of SERT? On the other words, SERT would affect the amount of released serotonin within (presynaptic membrane) nerve terminal on stage 1.  Would it be correct?

Do you have any suggestions?
Thank you very much for any suggestions (^v^)

Serotonin is released via exocytosis (pockets of internal membrane holding serotonin released out into the synaptic cleft); it's not via a specialized "serotonin protein". Like I mentioned, SERT is a completely different protein whose simple job is to vacuum up the serotonin once it's no longer needed.