a type of drug that works by enhancing the action of the neurotransmitter gaba
gamma-Aminobutyric acid In general, GABA does not cross the blood–brain barrier,[50] although certain areas of the brain that have no effective blood–brain barrier, such as the periventricular nucleus, can be reached by drugs such as systemically injected GABA.[57] At least one study suggests that orally administered GABA increases the amount of human growth hormone (HGH).[58] GABA directly injected to the brain has been reported to have both stimulatory and inhibitory effects on the production of growth hormone, depending on the physiology of the individual.[57] Certain pro-drugs of GABA (ex. picamilon) have been developed to permeate the blood–brain barrier, then separate into GABA and the carrier molecule once inside the brain. This allows for a direct increase of GABA levels throughout all areas of the brain, in a manner following the distribution pattern of the pro-drug prior to metabolism.[citation needed]
Selective serotonin reuptake inhibitor The exact mechanism of action of SSRIs is unknown.[2] SSRIs are believed to increase the extracellular level of the neurotransmitter serotonin by limiting its reabsorption (reuptake) into the presynaptic cell, increasing the level of serotonin in the synaptic cleft available to bind to the postsynaptic receptor. They have varying degrees of selectivity for the other monoamine transporters, with pure SSRIs having only weak affinity for the norepinephrine and dopamine transporters.