سَجيل | Sajeel

"I have ADHD. Why does caffeine make me sleepy sometimes? " It's an allosteric interaction inside A₂A–D₂ receptor complexes. Caffeine works primarily as a non-selective antagonist of adenosine receptors. Adenosine is a neuromodulator that accumulates in the brain the longer you stay awake. The two receptors most relevant to caffeine are: -A₁ is widely distributed and its activation generally inhibits neurotransmitter release (including glutamate and dopamine in some areas). A₂A is concentrated especially in the striatum (and other basal ganglia areas). Activation of A₂A has opposing effects on dopamine signaling. Caffeine is a non-selective antagonist, meaning it binds to both A₁ and A₂A receptors without activating them, simply occupying the site so adenosine cannot. In the striatum, A₂A and D₂ receptors physically form heteromeric complexes. This close physical association allows direct allosteric modulation between the two receptors.⁠ When adenosine binds to the A₂A receptor in this complex: -It decreases the affinity of the coupled D₂ receptor for dopamine (and for D₂ agonists). -It reduces the intrinsic efficacy of dopamine signaling through D₂. In practical terms, adenosine makes the D₂ receptor less sensitive and less effective. Stimulating A₂A receptors increases the dissociation constant (Kd) of D₂ agonist binding, meaning dopamine binds less tightly and the receptor responds more weakly. By occupying A₂A receptors, caffeine prevents adenosine from binding and exerting that negative allosteric modulation. The brake is lifted, so existing dopamine can activate D₂ receptors more effectively (higher affinity and better signaling). So it does not cause a large release of new dopamine the way amphetamines or cocaine do. Instead, it improves the efficiency of the dopamine that is already present. So caffeine can increase the apparent availability or function of D₂ receptors without flooding the system with extra dopamine. Now your ADHD brain typically has lower baseline levels of dopamine and/or fewer available receptors. Without enough dopamine, your brain constantly "hunts" for stimulation. So when caffeine bumps your dopamine up into a "normal" range, it satisfies that hunger. Then there are other possibilities, such as vasoconstriction. Caffeine acts as a central nervous system vasoconstrictor, meaning it temporarily narrows the blood vessels in your brain and modifies blood flow. In some individuals with ADHD, this reduction in cerebral blood flow actually decreases overactivity in certain regions of the brain, thus having a minor sedative-like effect. Also, don't feel some bs pressure to overconsume caffeine because it's linked to "longevity". Roughly 95% of the caffeine you drink is broken down by a single liver enzyme made by the CYP1A2 gene. Depending on the specific variant (specifically the single nucleotide polymorphism rs762551) you inherit, you fall into one of two main categories: -Fast metabolizers (AA Genotype) These people process caffeine up to four times faster than slow metabolizers. Because caffeine leaves their system quickly, they avoid its negative cardiovascular side effects while still absorbing coffee’s beneficial antioxidants and polyphenols. For this group, moderate coffee consumption actually lowers the risk of heart attacks and high blood pressure. -Slow metabolizers (C-allele carriers) These people possess a variant that causes caffeine to linger in the bloodstream for hours. For them, heavy coffee consumption strains the heart, significantly increasing the risk of high blood pressure and nonfatal heart attacks. The following study for example discovered that drinking 2 to 3 cups of coffee per day increased the risk of a nonfatal heart attack by 36% in slow metabolizers. For those drinking 4 or more cups daily, the risk skyrocketed by 64%. fitandball.gumroad.com/l/bra…