Tranquilizers

Tranquilizers act as anti-anxiety agents by depressing the central nervous system without leading to sedation. Barbiturates are seldom used now for managing anxiety or dysphoria because of their addictive potential. The molecules of barbiturate drugs pass through the membranes of the cells in the brain. They are then able to block nerve signals that pass from cell to cell, thus inhibiting the stimulation and conduction of chemical neurotransmitters between the cells. In addition, barbiturates are able to reduce the effect of abnormal electrical activity in the brain which cause seizures, such as in the case of epilepsy. Phenobarbital is a barbiturate that performs this function exceptionally well, therefore it is still useful as an anticonvulsant drug.

Depressant drugs, like alcohol and barbiturates, just as stimulant drugs, like cocaine and amphetamines, all appear to have the ability to stimulate the brain's reward circuit. The behavioral effect of this action is to increase the need for more of the drug, usually to get the same effect (drug tolerance). If it is being taken for its effect as a euphoric, more of the drug is needed each time it is taken to produce a high or for sleep if it is being used as a sedative. Drugs that stimulate the brain reward centers also have the effect of excluding other types of reward sensations like those from food or sex.

Drugs that stimulate the brain reward centers seem to enhance the presence of a chemical found in the brain called gamma aminobutyric acid (GABA). GABA has the effect of quieting the neurons where the GABA receptors are found.

The newer benzodiazepine tranquilizers reduce neuron sensitivity only for cells that do have the GABA receptor sites, but the barbiturates are able to work the sedating effect elsewhere as well, wherever there are chloride channels. That difference in action may account for the higher degree of sedation afforded by the barbiturates over the benzodiazepines. Both types of drugs are able to affect the brain's reward center by increasing the amount of dopamine released into the limbic system, the part of the brain that regulates certain biological functions such as sleep and the emotions.