CCK-4
Encyclopedia
Cholecystokinin tetrapeptide (CCK-4, Trp
-Met
-Asp-Phe
-NH2; also PTK7) is a peptide
fragment derived from the larger peptide hormone cholecystokinin
. Unlike cholecystokin which has a variety of roles in the gastrointenstinal system as well as central nervous system
effects, CCK-4 acts primarily in the brain as an anxiogenic
, although it does retain some GI effects, but not as much as CCK-8 or the full length polypeptide CCK-58.
CCK-4 reliably causes severe anxiety
symptoms when administered to humans in a dose of as little as 50μg,
and is commonly used in scientific research to induce panic attack
s for the purpose of testing new anxiolytic
drugs.
Since it is a peptide, CCK-4 must be administered by injection, and is rapidly broken down once inside the body so has only a short duration of action, although numerous synthetic analogues with modified properties are known.
Tryptophan
Tryptophan is one of the 20 standard amino acids, as well as an essential amino acid in the human diet. It is encoded in the standard genetic code as the codon UGG...
-Met
Methionine
Methionine is an α-amino acid with the chemical formula HO2CCHCH2CH2SCH3. This essential amino acid is classified as nonpolar. This amino-acid is coded by the codon AUG, also known as the initiation codon, since it indicates mRNA's coding region where translation into protein...
-Asp-Phe
Phenylalanine
Phenylalanine is an α-amino acid with the formula C6H5CH2CHCOOH. This essential amino acid is classified as nonpolar because of the hydrophobic nature of the benzyl side chain. L-Phenylalanine is an electrically neutral amino acid, one of the twenty common amino acids used to biochemically form...
-NH2; also PTK7) is a peptide
Peptide
Peptides are short polymers of amino acid monomers linked by peptide bonds. They are distinguished from proteins on the basis of size, typically containing less than 50 monomer units. The shortest peptides are dipeptides, consisting of two amino acids joined by a single peptide bond...
fragment derived from the larger peptide hormone cholecystokinin
Cholecystokinin
Cholecystokinin is a peptide hormone of the gastrointestinal system responsible for stimulating the digestion of fat and protein...
. Unlike cholecystokin which has a variety of roles in the gastrointenstinal system as well as central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
effects, CCK-4 acts primarily in the brain as an anxiogenic
Anxiogenic
An anxiogenic substance is one that causes anxiety. Anxiogenic effects can be measured by, for example, the hole-board test in rats and mice. A number of agents are used to provoke anxiety or panic in experimental models...
, although it does retain some GI effects, but not as much as CCK-8 or the full length polypeptide CCK-58.
CCK-4 reliably causes severe anxiety
Anxiety
Anxiety is a psychological and physiological state characterized by somatic, emotional, cognitive, and behavioral components. The root meaning of the word anxiety is 'to vex or trouble'; in either presence or absence of psychological stress, anxiety can create feelings of fear, worry, uneasiness,...
symptoms when administered to humans in a dose of as little as 50μg,
and is commonly used in scientific research to induce panic attack
Panic attack
Panic attacks are periods of intense fear or apprehension that are of sudden onset and of relatively brief duration. Panic attacks usually begin abruptly, reach a peak within 10 minutes, and subside over the next several hours...
s for the purpose of testing new anxiolytic
Anxiolytic
An anxiolytic is a drug used for the treatment of anxiety, and its related psychological and physical symptoms...
drugs.
Since it is a peptide, CCK-4 must be administered by injection, and is rapidly broken down once inside the body so has only a short duration of action, although numerous synthetic analogues with modified properties are known.