Actually,
Lev,
phenylethylamine (PEA) is a neurotransmitter; it is responsible for the condition commonly referred to as falling in love (and
one develops a tolerance to it within 18 to 24 months, which is why
most sexual relationships end after that time, unless other neurotransmitters
kick in). I think you're thinking of phenylalanine, which gradually
causes dementia (an unrelated, though some would argue superficially similar,
condition).