The endogenous opioid system: a common substrate in drug addiction.
Drug addiction is a chronic brain disorder leading to complex adaptive changes within the brain reward circuits that involve several neurotransmitters. One of the neurochemical systems that plays a pivotal role in different aspects of addiction is the endogenous opioid system (EOS). Opioid receptors and endogenous opioid peptides are largely distributed in the mesolimbic system and modulate dopaminergic activity within these reward circuits. Chronic exposure to the different prototypical drugs of abuse, including opioids, alcohol, nicotine, psychostimulants and cannabinoids has been reported to produce significant alterations within the EOS, which seem to play an important role in the development of the addictive process. In this review, we will describe the adaptive changes produced by different drugs of abuse on the EOS, and the current knowledge about the contribution of each component of this neurobiological system to their addictive properties.
Trigo
José Manuel
JM
Laboratori de Neurofarmacologia, Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, PRBB, Barcelona, Spain.
Martin-García
Elena
E
Berrendero
Fernando
F
Robledo
Patricia
P
Maldonado
Rafael
R
D000818:Animals; D006801:Humans; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology; D018847:Opioid Peptides / Q000502:physiology*; D009293:Opioid-Related Disorders / Q000209:etiology / Q000378:metabolism; D011957:Receptors, Opioid / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D019966:Substance-Related Disorders / Q000209:etiology / Q000378:metabolism
D018847:Opioid Peptides; D011957:Receptors, Opioid