Where is caffeine found?: in coffee, in many types of tea, energy drinks or medicines intended mainly for migraines:
https://www.adc.sk/databazy/humanne-lieky/ucinna-latka/kofein-4723.html
Caffeine, as I have noticed in practice, has a very strong affinity (acts very strongly) for acetylcholine receptors. In practice, this manifests itself, for example, in increased secretion of saliva and digestive juices (which is positive). Caffeine therefore also helps with weight loss very effectively.
How caffeine affects the brain
Caffeine is an antagonist of the main inhibitory glycine receptors in the brain. In layman’s terms, caffeine makes the entire (literally the entire) brain more active without any risks.
The antidepressant effects of caffeine are very strong. It helps with learning and completing school assignments. It helps with concentration during meditation.
The increased activity of adrenaline receptors also contributes to the strong antidepressant effect of caffeine. Caffeine increases the activity of adrenaline receptors indirectly on the basis of antagonism to adenosine receptors (there is a scientific study that says that adenosine is an antagonist to adrenaline receptors).
Since caffeine is an antagonist of adenosine receptors, it reduces the penetration of any psychoactive substance into the brain (including nicotine, alcohol, psychiatric and neurological drugs), which in practice means that it reduces the effects of any psychoactive substance. (There are scientific studies that say that substances that are adenosine agonists help penetrate any psychoactive substance into the brain).
We could call caffeine a substance that works in exactly the opposite way to alcohol – in a simplified and generalized way, this is literally true. Alcohol is an agonist on adenosine receptors (plus it has other effects), caffeine is an antagonist (this is mainly reflected in blood pressure). Alcohol is an agonist on the most important inhibitory receptors, caffeine is an antagonist on also inhibitory receptors (GABA), which are among the most important and most represented in the brain. Simply put, alcohol reduces the activity of the entire brain and caffeine increases it.
Caffeine should theoretically significantly block the effects of addictive benzodiazepine-sedatives (based on a less direct mechanism). Sedatives are agonists of inhibitory receptors (GABA).
Combining caffeine with cannabis may not be the best solution, because both THC and caffeine are antagonists of very abundantly represented inhibitory receptors, which in practice can cause the entire brain to become overly active. Anyone with a tendency towards epilepsy might not have a good outcome. On the other hand, the combination of both substances can be quite interesting and can significantly and visibly change the overall characteristics of the psychoactive effect of cannabis.
On the one hand, caffeine hinders the penetration of psychiatric drugs into the brain to a certain extent, and on the other hand, it can enhance the effects of drugs that work by increasing the activity of any receptor (with the exception of purely inhibitory receptors such as GABA and glycine receptors).
Caffeine has strong antidepressant effects but causes anxiety. In psychiatry, the word anxiety has a completely different meaning than in lay use. Anxiety is associated with palpitations, high blood pressure and heart rate, sweating, etc., caused by a psychological stimulus or a mental disorder.
Since caffeine increases blood pressure, which is its disadvantage, it is good to combine it with a beta-blocker, dipyridamole, or even drugs for erectile dysfunction in men (including the popular Viagra), which are agonists of adenosine receptors, theophylline, and similar substances.
Of course, the most practical thing to do is to use a beta-blocker.
Caffeine may not have a very positive effect on people with epilepsy.
https://en.wikipedia.org/wiki/Caffeine#Pharmacology
References:
Adenosine receptor signaling: a key to opening the blood–brain door https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4557218/
Blood-brain barrier transport and brain metabolism of adenosine and adenosine analogs. https://www.ncbi.nlm.nih.gov/pubmed/8301550
Brain to blood efflux transport of adenosine: blood-brain barrier studies in the rat. https://www.ncbi.nlm.nih.gov/pubmed/15228584
Adenosine receptor signaling modulates permeability of the blood-brain barrier https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3328085/
https://en.wikipedia.org/wiki/Glycine_receptor
https://en.wikipedia.org/wiki/GABA_receptor
https://en.wikipedia.org/wiki/Caffeine