22.09.2015
Orexin, also called hypocretin, is a neurotransmitter that regulates arousal, wakefulness, and appetite. The brain contains about 10,000 to 20,000 neurons in the hypothalamus,  but axons from these neurons extend throughout the entire brain and spinal cord, where there are also receptors for orexin (R).
As you’ll see there are many hormones and other systems in the body that interact with orexin. Therefore, the orexin system is central to us functioning as productive human beings and being in a good mood.
Orexin also increases hunger, and this works via increased neuropeptide Y expression in the arcuate nucleus of the hypothalamus (R). This orexin system interacts with so many other systems of the body, which makes it so important. Orexin is particularly important in people with narcolepsy, which is an autoimmune condition that destroys orexin neurons.
This is actually the most important factor in orexin being suppressed: chronic inflammation. Elevated inflammation from cytokines like IL-1b (R) and TNF (R) cause fatigue by suppressing of orexin neurons (R, R2). A 2007 study found acidification of our blood increases excitability of orexin, whereas alkalinization depresses it. Interval exercise especially leads to a surge in lactate, which you will read is important for exciting orexin, regardless of acidity. Exercise can increase wakefulness even without the orexin system, so it’s good anyway.
There is no direct research showing ICES increases Orexin, but my personal experience leads to me to think that it does. I believe the main mechanisms by which ICES increases orexin is by decreasing  inflammation and potently increasing ATP production.
ATP is the main energy related molecule that we produce and when they’re deficient, orexin is suppressed. Supplying orexin neurons with lactate and can stop glucose from blocking orexin neurons (R). One study hypothesized that orexin neurons only ‘see’ glucose changes when the levels of other energy molecules are low, whereas high energy levels can stop glucose from regulating orexin cells (R). Nonessential amino acids were more potent in activating orexin cells than essential amino acids (R).


Amino acids blocked the glucose suppression of orexin because it tells the neurons that there’s enough energy around (R). The  hypothesis is that under low-energy conditions such as starvation or anorexia, it could be advantageous for ingested glucose to suppress the orexin-driven net energy expenditure, thereby ensuring that more fundamental processes (such as keeping the brain alive) receive enough glucose. If you eat less or practice some degree of caloric restriction you will increase orexin because our body senses we’re not getting enough calories and activates this system. Sugar (both glucose and fructose) increases GLP-1 as a satiety signal, but glucose also suppresses orexin and excess fructose isn’t a good idea. Hi-maize produces butyrate, which is an energy related molecule and should therefore block glucose-induced suppression of orexin (R).
Also, butyric acid is acidic and increases ATP and therefore may also increase orexin in these ways. As discussed above, it also is a GLP-1 agonist, so it can increase orexin in multiple ways.
A study found having fun or play was able to increase orexin, while the same level of exercise wasn’t able to (R). The study concludes that motor and cardiovascular changes are not sufficient to elevate orexin, so they hypothesize that the emotional aspects of yard play account for the observed increase in orexin (R). I haven’t seen any studies about ketosis and orexin directly, but I have some theories about how it may stimulate orexin. First, if you get into ketosis, glucose levels will likely be low, which is a significant factor in activating orexin. Third, Ketones are  acidic and they increase our blood acidity, which in turn increases orexin.
Forskolin increases cyclic AMP in the whole body, including in the area where orexin neurons are. Ghrelin increases orexin (R) and this is part of the mechanism by which ghrelin increases hunger (R). Specifically, it increases the levels of orexin A in the dorsomedial hypothalamic nucleus (DMH) and orexin B in the DMH and paraventricular nucleus (PVN) among the six hypothalamic regions that were examined.
In addition, long term nicotine usage increases the orexin receptors (R), which will make you more sensitive to a given amount of orexin. In addition, nicotine and orexin excite the same synapses of the arousal pathway within the prefrontal cortex (thalamocortical). Nicotine addiction depends, in part, on leptin and orexin (R) and in particular orexin-1 receptors in the lateral hypothalamus.


As mentioned before, Fructose, Fructans and FOS can also excite orexin neurons by increasing GLP-1, thereby increasing wakefulness (R, R2). Heavy fructose consumption may not be the most healthy way to increase orexin, but based on my experience, it’s effective. A study found that in healthy people, there was a correlation between omega 3’s and orexin A (but not in the narcoleptics). CRH or Corticotrophin Releasing Hormone is released by the hypothalamus and activates orexin. Cannabinoids (R, R2)…Although orexins play a role in the addictive properties of cannabinoids. Orexin plays a role in causing Alzheimer’s disease by increasing amyloid plaques (R). Orexin neurons in the lateral hypothalamic area (LHA) and posterior hypothalamus (PH) are anatomically well placed to provide a link between the limbic system, systems involved in energy homeostasis and monoaminergic and cholinergic neurons in the brain stem. The orexin neurons innervate and excite many brain regions that drive arousal and attention, including the locus coeruleus and the dorsal raphe.
Rewarding stimuli trigger release of dopamine from the mesolimbic projections between the ventral tegmental area and the nucleus accumbens, and orexins enhance signaling in this pathway. Please note that distributions of orexin fibres and receptors (OX1R, OX2R) are predicted from the results of studies on rodent brains, as it is on rodents that most histological studies on the orexin system have been carried out. Orexin neurons also have links with the reward system through the ventral tegmental area (VTA, containing dopamine) and with the hypothalamic nuclei that stimulate feeding behaviour.
Peripheral metabolic signals such as leptin, ghrelin and glucose influence orexin neuronal activity to coordinate arousal and energy homeostasis. The nucleus suprachiasmaticus (SCN), the central body clock, sends signals to orexin neurons via the dorsomedial hypothalamus (DMH).
Input from the limbic system (amygdala and bed nucleus of the stria terminalis (BST)) might regulate the activity of orexin neurons upon emotional stimuli to evoke emotional arousal or fear-related responses61, 62.



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