transporter

n. a protein complex that spans a cell membrane and conveys ions, neurotransmitters, or other substances between the exterior and interior of the cell. For example, at synapses between neurons, transporters in the presynaptic membrane recognize and bind to neurotransmitter molecules and return them to the presynaptic neuron for reuse (see reuptake). Transporters may utilize passive transport, in which a substance is transported into or out of a cell according to its concentration gradient across the cell membrane; or active transport, which is an energy-dependent process often relying on the hydrolysis of ATP to provide energy to facilitate movement of a substance from one side of the cell membrane to the other.

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Psychology term of the day

May 8th 2024

sedative, hypnotic, and anxiolytic drug

any of a group of CNS depressants that have been developed for therapeutic use because of their calming effect (i.e., sedative) and ability to induce sleep (i.e., hypnotic) and reduce anxiety (i.e., anxiolytic). They include the barbiturates, meprobamate, and the benzodiazepines. At low doses, these drugs are prescribed for daytime use to reduce anxiety; at higher doses, many of the same drugs are prescribed as sleeping pills. Although efficacious when used sparingly, over the long term all induce marked tolerance, and cessation of use can precipitate potentially life-threatening withdrawal phenomena. Acute abuse can yield dangerous intoxication effects, and chronic abuse can cause a range of serious, irreversible conditions.