22) ENKEPHALIN

[Editor]

a) is a pentapeptide
b) is the same as endorphin?
c) has a long half life in the brain
d) is found mainly in the pituitary
e) is an agonist at opiate receptors but is not antagonized by naloxone

[Editor]

TFFFF

Methionine and leucine enkephalin both have 5 amino acids
Enkephalins are endogenous delta opiod receptor agonists involved in the regulation of pain (the gate control theory)
Endorphins are also found in the CNS and are formed from lipotrophin. They have 31 amino acids and are opiod receptor agonists ( mu and delta).Both have a half life of a few seconds.
Enkephalins are mainly found where there is a high concentration of opiate receptors ( PAG, PVG, raphe nucleus, and substantia gelatinosa of the spinal cord) Endorphins are mainly located in the anterior hypothalamus.
The definition of an opiate agonist is “a drug whose Intrinsic activity can be reversed by the action of naloxone”.