What gives you high?

Answer 1

It depends on which substance is taken, different drugs have different modes of action and different target areas in the brain. Stimulants for example, work on the neurotransmitter Dopamine, either through releasing more Dopamine into the synapses (the small gaps between the ends of each "string" of nerve fiber) or the re-uptake of Dopamine thus increasing the effects of the Dopamine already present in the synapses.

Most other drugs work in similar ways but by targeting other neurotransmitters. The drugs have a molecular structure that is very similar but slightly different to that of the neurotransmitter it targets, and because of this it fits on for example the Dopamine receptors (receptors are "keyholes" in which only a specific type of "key" fits to activate it, namely the neurotransmitter it is designed for) in the nerves thus mimicking Dopamine in it's effects. The same goes for most other types of drugs, such as Opioids which target the mu and kappa opioid receptors, most Hallucinogens which target the 5HT serotonin receptors, most Dissociatives which target the NMDA receptors and most Depressants such as Alcohol and tranquilizers which target the GABA-A receptors and it's sub-receptors.