The scaffold of all neurotransmitters
Phenylethylamine (PEA, C₈H₁₁N) is perhaps the most structurally important small molecule in neurochemistry — it is the scaffold from which nature built most monoaminergic neurotransmitters: dopamine (+two ring –OH groups), noradrenaline (+chain –OH), adrenaline (+N-methyl), serotonin (indole variant), and many psychoactive drugs (amphetamine = PEA + α-methyl; mescaline = PEA + three ring methoxy groups).
Mechanism: the dopamine amplifier
PEA activates TAAR1 receptors (Trace Amine-Associated Receptor 1) in dopaminergic and serotonergic neurons, increasing the release of existing dopamine and noradrenaline pools. It is essentially a dopamine system amplifier: in its presence, each action potential of a dopaminergic neuron releases more dopamine. Result: greater activity in the reward system, mild euphoria, increased alertness and focus — the neurochemical profile of falling in love.
PEA in cacao: concentration and bioavailability
Cacao contains 0.1–0.7 µg/g of PEA. However, oral PEA is degraded by MAO-B so rapidly (half-life 5–10 minutes) that negligible amounts reach the brain at dietary doses. The "cacao makes you fall in love" claim is poetically true but mechanistically overstated.
The complete picture
Chocolate's genuine mood effects come from a synergy: PEA (small contribution), anandamide (endocannabinoid, CB1 agonist), N-oleoylethanolamide (FAAH inhibitor that prolongs endogenous anandamide), theobromine + caffeine (gentle sustained stimulation), and magnesium (~500 mg/100g in pure cacao, cofactor for serotonin synthesis enzymes).
PEA deficiency and depression
Depressed patients consistently show reduced urinary phenylacetic acid (PEA metabolite) — suggesting lower PEA synthesis or higher MAO-B degradation. MAO-B inhibitors (selegiline, used in Parkinson's) increase brain PEA and have documented antidepressant effects. TAAR1 agonists are currently in Phase II clinical trials for depression and schizophrenia.