• Nutrients used in the normal synthesis and metabolism of neurotransmitters
• Absorption/Inhalation of other chemicals add to the "mix"
• Not all these chemicals are good -- neurotoxicology (see below).
• Blood-Brain Barrier protects you somewhat from some dangers
• not young children, though.  This puts them at greater risk (e.g. lead poisoning)
• Generally, there's a balance:
• Release
• Reuptake/Deactivation.

• Acetylcholine (attention, arousal, memory)
• Monoamines: Dopamine, norepinephrine, serotonin (movement, arousal, pleasure/mood)
• GABA (inhibition of anxiety, excitability)
• Endorphins ("endogenous morphines," runner's high)

• Reinforcing brain stimulation releases dopamine...
• The Cocaine story.  Prolongs the effect of dopamine in synapses.
• Falling in love?  Solving a hard math problem? Swept away by a symphony?
• Are all of these the same "mechanism?"  The story is not yet clear.

• Psychoactive drugs act as AGONISTS or as ANTAGONISTS for neurotransmitters.
• Stimulants (amphetamine, cocaine, MDMA) alter the monoamines...
• Narcotics (heroin, morphine) alter endorphins
• Sedatives (Seconal, Quaalude, ... alcohol) alter GABA
• Hallucinogens (LSD, Mescaline, Pot, Glue sniffing) alter serotonin

G. Drugs and Toxicology (poisons)

• All things are toxic -- "The dose makes the poison" Paracelsus.
• Use, Maladaptive Use, Dependence (tolerance), Abuse
• Habits can kill you.
• Tobacco, alcohol (the biggest killers. True cost of a pack of cig's: $20.  Alcohol $99 Billion/yr)
• Other drugs (... In total, including legal costs, $67 Billion/yr)
• Environmental poisons too are psychoactive.
• Metals (Lead, Mercury, Manganese).
• Dangers of Lead on brain injury was known in 1840.  But information supressed by the Paint industry and by the Automotive industry until Herb Needleman's 1979 study showed low levels of lead poisoning harmed children in Boston .
• Pesticides (Military Nerve Gas is related to many pesticides commonly used)
• Industrial solvents intoxicate and make alcohol more dangerous.