Kelatorphan is a drug

Drug

A drug, broadly speaking, is any substance that, when absorbed into the body of a living organism, alters normal bodily function. There is no single, precise definition, as there are different meanings in drug control law, government regulations, medicine, and colloquial usage.In pharmacology, a...

 which acts as a powerful and complete inhibitor

Enzyme inhibitor

An enzyme inhibitor is a molecule that binds to enzymes and decreases their activity. Since blocking an enzyme's activity can kill a pathogen or correct a metabolic imbalance, many drugs are enzyme inhibitors. They are also used as herbicides and pesticides...

 of nearly all of the enzyme

Enzyme

Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

s responsible for catabolism

Catabolism

Catabolism is the set of metabolic pathways that break down molecules into smaller units and release energy. In catabolism, large molecules such as polysaccharides, lipids, nucleic acids and proteins are broken down into smaller units such as monosaccharides, fatty acids, nucleotides, and amino...

 of the endogenous

Endogenous

Endogenous substances are those that originate from within an organism, tissue, or cell. Endogenous retroviruses are caused by ancient infections of germ cells in humans, mammals and other vertebrates...

 enkephalin

Enkephalin

An enkephalin is a pentapeptide involved in regulating nociception in the body. The enkephalins are termed endogenous ligands, or specifically endorphins, as they are internally derived and bind to the body's opioid receptors. Discovered in 1975, two forms of enkephalin were revealed, one...

s, including neutral endopeptidase (NEP), dipeptidyl peptidase III (DPP3), aminopeptidase N (APN), and angiotensin-converting enzyme

Angiotensin-converting enzyme

Angiotensin I-converting enzyme , an exopeptidase, is a circulating enzyme that participates in the body's renin-angiotensin system , which mediates extracellular volume , and arterial vasoconstriction...

 (ACE). In mice, with the intracerebroventricular co-administration of a 50 µg dose of kelatorphan (this route is necessary because kelatorphan is incapable of crossing the blood-brain-barrier) hence alongside exogenous

Exogenous

Exogenous refers to an action or object coming from outside a system. It is the opposite of endogenous, something generated from within the system....

 [Met]enkephalin

Met-enkephalin

[Met]enkephalin, sometimes referred to as opioid growth factor , is a naturally-occurring, endogenous opioid peptide that has opioid effects of a relatively short duration. It is one of the two forms of enkephalin, the other being [leu]enkephalin...

 (ED₅₀

ED50

ED 50 is a geodetic datum which was defined after World War II for the international connection of geodetic networks....

 approximately 10 ng), it potentiated the analgesic

Analgesic

An analgesic is any member of the group of drugs used to relieve pain . The word analgesic derives from Greek an- and algos ....

 effects of the latter by 50,000 times. Kelatorphan also displays potent

Potency (pharmacology)

In the field of pharmacology, potency is a measure of drug activity expressed in terms of the amount required to produce an effect of given intensity. A highly potent drug evokes a larger response at low concentrations, while a drug of lower potency evokes a small response at low concentrations...

 antinociceptive effects alone, and does not depress respiration

Respiration

Respiration may refer to:Biology* Respiratory system, the anatomical system of an organism used for respiration* Cellular respiration, the process in which nutrients are converted into useful energy in a cell...

, although at high doses it actually increases it.