Nootropic Glossary
Acetylcholine
A neurotransmitter critical for memory formation, learning, and attention. Many nootropics work by increasing acetylcholine levels — either by providing precursors (Alpha-GPC, CDP-Choline), inhibiting breakdown (Huperzine A), or increasing receptor sensitivity (racetams).
Adaptogen
A natural compound that helps the body resist and adapt to physical and mental stress. Adaptogens modulate the HPA axis and cortisol levels. Common examples include Ashwagandha, Rhodiola Rosea, and Panax Ginseng. Effects typically build over weeks of consistent use.
AMPA Receptor
A type of glutamate receptor involved in fast excitatory neurotransmission and synaptic plasticity. Racetams are positive allosteric modulators of AMPA receptors, meaning they enhance receptor function without directly activating it. AMPA receptor activity is essential for learning and memory.
BDNF
Brain-Derived Neurotrophic Factor — a protein that supports neuron survival, growth, and synaptic plasticity. Higher BDNF levels are associated with better memory and mood. Exercise, Lion's Mane, and several nootropics increase BDNF expression.
Bioavailability
The percentage of an administered compound that reaches the bloodstream in active form. Oral bioavailability varies widely among nootropics. Fat-soluble compounds (Aniracetam, Pramiracetam) must be taken with dietary fat. Sublingual administration bypasses first-pass liver metabolism for higher bioavailability.
Blood-Brain Barrier
A selective membrane that separates circulating blood from the brain. Only certain molecules can cross it. Many nootropics are specifically designed or selected for their ability to penetrate this barrier (e.g., Magnesium L-Threonate vs other magnesium forms).
Cholinergic
Relating to the neurotransmitter acetylcholine. Cholinergic nootropics increase acetylcholine availability through precursor supplementation (Alpha-GPC, CDP-Choline), enzyme inhibition (Huperzine A), or enhanced choline uptake (Coluracetam).
Cycling
The practice of alternating periods of use and non-use of a nootropic to prevent tolerance buildup. For example, Phenylpiracetam is typically cycled due to rapid tolerance development. Common protocols include 5 days on/2 days off or 4 weeks on/1 week off.
Dopamine
A neurotransmitter involved in motivation, reward, focus, and motor control. Many stimulant nootropics (caffeine, modafinil, phenylpiracetam) work by increasing dopamine availability. Tyrosine (NALT) provides the raw material for dopamine synthesis.
Eugeroic
A class of wakefulness-promoting agents that differ from traditional stimulants in mechanism and side effect profile. Modafinil and Adrafinil are eugeroics — they promote wakefulness primarily through orexin and histamine pathways rather than catecholamine release.
GABA
Gamma-aminobutyric acid — the brain's primary inhibitory neurotransmitter. GABA reduces neuronal excitability, producing calming effects. Phenibut and Ashwagandha modulate GABA receptors. GABA supplements themselves do not cross the blood-brain barrier effectively.
Glutamate
The brain's primary excitatory neurotransmitter, essential for learning, memory, and synaptic plasticity. Racetams modulate glutamate receptors (AMPA and NMDA). Excessive glutamate causes excitotoxicity — neuronal damage from overactivation.
Half-Life
The time required for the concentration of a substance in the body to decrease by half. Determines dosing frequency and duration of effects. Caffeine's half-life of 5 hours means half the caffeine from morning coffee is still active at mid-afternoon.
Neurogenesis
The process of generating new neurons from neural stem cells. Occurs primarily in the hippocampus (memory center) and olfactory bulb. Lion's Mane, exercise, and BDNF-enhancing compounds support neurogenesis. Previously thought impossible in adults, now confirmed to occur throughout life.
Neuroprotection
The preservation of neuronal structure and function against damage from oxidative stress, inflammation, excitotoxicity, or aging. Neuroprotective nootropics include NAC (antioxidant), Lion's Mane (NGF stimulation), CoQ10 (mitochondrial protection), and Omega-3 DHA (membrane integrity).
NGF
Nerve Growth Factor — a protein that promotes the survival, development, and function of neurons. Lion's Mane mushroom is the only known natural compound that stimulates NGF production. NGF is particularly important for neurons in the hippocampus and peripheral nervous system.
NMDA Receptor
A glutamate receptor critical for synaptic plasticity and memory formation. Requires both glutamate and glycine (co-agonist) to activate. Magnesium naturally blocks NMDA receptors at resting potential — depolarization removes the magnesium block. Several nootropics modulate NMDA function.
Nootropic
A substance that enhances cognitive function without significant side effects. Coined by Corneliu Giurgea in 1972, who defined nootropics as compounds that enhance learning, resist cognitive impairment, protect the brain, increase neural coupling, and lack sedation or toxicity.
Prodrug
An inactive compound that is metabolized in the body to produce the active drug. Adrafinil is a prodrug of modafinil — the liver converts adrafinil into modafinil. Prodrugs often have delayed onset and may place additional load on the liver.
Racetam
A family of synthetic nootropics sharing a pyrrolidone nucleus. Includes Piracetam, Aniracetam, Oxiracetam, Phenylpiracetam, and others. Racetams primarily modulate glutamate (AMPA) receptors and increase acetylcholine demand. The original nootropic class.
Stack
A combination of two or more nootropics taken together for synergistic cognitive effects. The most basic stack is caffeine + L-theanine. Well-designed stacks target complementary neurotransmitter systems (e.g., racetam + choline source).
Sublingual
Administration by placing a substance under the tongue, where it absorbs through the mucous membrane directly into the bloodstream. Bypasses first-pass liver metabolism, providing faster onset and higher bioavailability. Common for Noopept, Coluracetam, and Uridine.
Synaptic Plasticity
The ability of synapses (connections between neurons) to strengthen or weaken over time in response to activity. Long-term potentiation (LTP) — the strengthening of synapses — is the biological basis of learning and memory. Most cognitive nootropics ultimately enhance synaptic plasticity.
Tolerance
The diminishing response to a substance after repeated use, requiring higher doses to achieve the same effect. Tolerance develops at different rates: caffeine (weeks), phenylpiracetam (days), phenibut (days). Cycling protocols help prevent or reset tolerance.