Cocaine lowers the levels of a chemical messenger in the brain called enkephalin.Researchers have found the number of enkephalin receptors to be higher in cocaine addicts than nonaddicted people.This is an example of

Question

Quizplus · Accepted Answer

Up regulation refers to an increase in the number of receptors for a particular chemical messenger in response to chronic exposure to its ligand. In this case, the chronic exposure to cocaine leads to an up regulation of enkephalin receptors in the brain of addicts. This is a compensatory mechanism that occurs in an attempt to maintain normal brain function despite the inhibitory effect of cocaine on enkephalin release.

Cocaine Lowers the Levels of a Chemical Messenger in the Brain