Content area
Full text
Opioid peptides produced in the body act as neuromodulators that modify the actions of other neurotransmitters in the central nervous system. By altering the electrical properties of their target neurons, thereby making these neurons more difficult to excite, opioid peptides can influence the release of various neurotransmitters. As a result of this modulation, opioid peptides can-among other functions-induce pain relief and euphoria as well as affect certain behaviors, including alcohol consumption. Alcohol can activate the opioid peptide system. This mechanism may contribute to alcohol reinforcement and excessive alcohol consumption, because agents that inhibit the opioid peptide system decrease alcohol selfadministration in animals and reduce craving and alcohol consumption in human alcoholics. Moreover, a genetically determined, increased responsiveness of the opioid system to alcohol may contribute to a predisposition for alcoholism in some people. KEY WORDS: endogenous opioids; peptides; drug interaction; neurotransmitters; opioid receptors; central nervous system; brain; neuron; biological activation; reinforcement; AOD use behavior; self administration of drugs; AOD craving; AOD sensitivity; AOD use susceptibility; euphoria; sense of pain; literature review
Endogenous opioid peptides' are small molecules that are naturally produced in the central nervous system (CNS) and in various glands throughout the body, such as the pituitary and adrenal glands. These peptides produce the same effects as the chemicals known as classic alkaloid opiates, which include morphine and heroin. Endogenous opioid peptides function both as hormones and as neuromodulators. Endogenous opioid peptides that serve as hormones are secreted into the circulation by the producing glands and are delivered to a variety of distant target tissues where they induce a response. Endogenous opioid peptides that serve as neuromodulators are produced and secreted by nerve cells (i.e., neurons) and act in the brain and spinal cord to modulate the actions of other neurotransmitters. (For more information on these neurotransmitters, see the related articles in this section.) Through these two mechanisms, endogenous opioid peptides produce many effects, ranging from preventing diarrhea to inducing euphoria and pain relief (i.e., analgesia).
This article reviews the physiology of endogenous opioid peptides and their interactions with other neurotransmitters. In addition, the article summarizes the interactions between alcohol and the endogenous opioid system and presents evidence that opioid peptides play a role in alcohol reinforcement. (For further information on alcohol and...