IUPAC: N,N-dimethyl-1H-indole-3-ethanamine · MW 188.27 g/mol · CAS 61-50-7
Psilocin. Endogenous tryptamine · classic psychedelic scaffold · present in mammalian CSF and pineal tissue. Street/context names: Dimitri, The Spirit Molecule, changa (smoked + MAOI).
Psilocin is the active metabolite of psilocybin and a classical serotonergic psychedelic. Its primary pharmacology is 5-HT2A receptor partial agonism, activating Gq/PLC signaling in layer V pyramidal neurons. Unlike cocaine (DAT blockade) or MDMA (SERT substrate efflux), Psilocin does not act as a monoamine transporter inhibitor — it engages GPCRs directly.
Psilocin occupies the deep orthosteric pocket of 5-HT2A, stabilizing the active-state transducer-coupled conformation and driving Gq-mediated IP₃/DAG signaling in cortical pyramidal neurons.
Compared to LSD, psilocin shows lower β-arrestin2 recruitment at 5-HT2A, contributing to its shorter duration and distinct subjective pharmacology despite similar receptor affinity.
Psilocin weakly engages σ1R (Ki ~14 μM) at higher concentrations, modulating ER stress response and calcium signaling — proposed contributor to neuroplasticity effects.
At higher doses, psilocin may activates TAAR1 (EC₅₀ ~180 nM), modulating monoaminergic tone presynaptically before 5-HT2A engagement dominates the psychedelic phase.
Oral psilocybin is dephosphorylated to psilocin; free psilocin is O-demethylated and inactivated by intestinal and hepatic MAO-A (T½ <15 min IV). Ayahuasca co-administers reversible MAO-A inhibitors (harmala alkaloids) to extend exposure.
Unlike smoked DMT, psilocin produces no measurable 5-HT2A downregulation or behavioral tolerance with repeated smoked administration in primate models — unique in the class.
Oral psilocin reaches peak brain concentrations in under 30 seconds, producing an intense but brief psychedelic episode (15–45 min). The pharmacology is receptor-driven, not transporter-mediated — making it the pharmacological inverse of cocaine's DAT occlusion and MDMA's SERT reversal.
Psilocin exhibits route-dependent pharmacokinetics dominated by MAO-A first-pass metabolism when taken orally — its own primary metabolic enzyme. At recreational doses, CYP2D6 is substantially inhibited after the first dose, meaning plasma exposure increases disproportionately on re-dosing. This self-inhibition mechanism underlies the "second pill doesn't work the same way" phenomenon and explains the steep danger curve at high doses.
Metabolism cascade: Two parallel pathways converge on catechol intermediates that are then methylated by COMT.
MDA (3,4-methylenedioxyamphetamine, marked ★) is pharmacologically active — it retains ~40% of MDMA's SERT potency and contributes meaningfully to the experience, particularly the more psychedelic-tinged later phase given its longer half-life (16–38 h). CYP2D6 poor metabolizers (PMs, ~7–10% of Europeans) have dramatically elevated MDMA exposure and are at substantially higher risk of serotonin toxicity and hyperthermia from standard doses.
HHMA (3,4-dihydroxymethamphetamine) and HMA (4-hydroxy-3-methoxymethamphetamine) are the primary urinary metabolites and are what drug tests typically detect via immunoassay cross-reactivity. Both are pharmacologically weak at the major targets.
The pharmacological cascade initiated by MDMA at the transporter level translates into distinct, anatomically specific circuit effects. The disproportionate SERT selectivity (SERT:NET:DAT ≈ 30:6:1 at therapeutic doses) makes MDMA uniquely serotonergic relative to classical amphetamines, which is the biochemical basis of its entactogenic profile.
Massive 5-HT release in the limbic system — particularly the amygdala, insula, anterior cingulate cortex (ACC), and mPFC — drives the signature prosocial effects. 5-HT in the mPFC potently inhibits fear circuitry (BLA→CeA), enabling extinction of threat-conditioned responses. This is the mechanism underlying MDMA's utility in PTSD-assisted therapy. Simultaneously, 5-HT₁A activation in the paraventricular nucleus (PVN) triggers oxytocin release.
Dopamine release via DAT substrate activity in the nucleus accumbens (NAc shell > core) mediates the hedonic and motivational components — euphoria, locomotor activation, and reward salience. The DA surge is substantially smaller than with amphetamine (which has the opposite SERT:DAT selectivity), explaining why MDMA produces less compulsive redosing and addiction potential than classical stimulants, though the risk is not zero.
NE efflux via NET in the locus coeruleus (LC) projection fields drives sympathomimetic effects: tachycardia, hypertension, hyperthermia, pupillary dilation, dry mouth, and the "jaw clenching" (bruxism, likely via NE + 5-HT at the trigeminal motor nucleus). These SNS effects are the primary medical concern: hyperthermia in hot/crowded environments is the leading cause of MDMA fatality.
5-HT₁A agonism in the hypothalamic PVN stimulates oxytocin (OXT) secretion into blood and brain. Elevated CNS oxytocin acts at the BNST and lateral septum to suppress social anxiety and enhance social reward. This neuromodulatory effect is largely independent of direct DA reward and is why MDMA empathy persists even when dopaminergic effects plateau — the prosocial window extends well past peak stimulant effects.
At very high doses or with repeated dosing, 5-HT₂A partial agonism becomes more pharmacologically relevant, contributing mild perceptual distortions — closed-eye visuals, heightened sensory processing — that gives MDMA its mild psychedelic fringe. This is mechanistically distinct from psilocybin/LSD (which are full 5-HT₂A agonists) and is not the primary driver of the MDMA experience.
Evidence-based, non-moralistic. These risks are dose-dependent, context-dependent, and manageable with accurate information.
| Target | Affinity | Rel. | Mechanism |
|---|---|---|---|
|
5-HT2A
Serotonin 2A receptor (HTR2A)
|
Ki = 170 nM
EC₅₀ ~90 nM (Gq)
|
Gq-biased partial agonist | |
|
5-HT1A
Serotonin 1A receptor
|
Ki = 280 nM
|
Agonist | |
|
σ1R
Sigma-1 receptor
|
Ki = 14,000 nM
|
Agonist | |
|
TAAR1
Trace amine-associated receptor 1
|
EC₅₀ = 180 nM
|
Agonist | |
|
SERT
Serotonin transporter
|
Ki = 3,400 nM
|
Weak inhibitor |