Bidirectional effects of opioids in motivational processes and the involvement of D1 dopamine receptors.
Exogenous and endogenous opioids significantly affect motivational processes; depending on the particular opioid receptor type with which they interact opposite effects are induced: activation of mu and delta opioid receptors is rewarding whereas activation of kappa opioid receptors induces aversive effects. Antagonism of mu-opioid receptors also induces aversion, suggesting the existence of a tonically active opioidergic reward pathway. There is evidence that beta-endorphin pathways arising from the hypothalamus play an important role in this respect. Opioid-induced reward as well as aversion seem to be mediated by the mesolimbic dopamine system, reward by increased, aversion by decreased transmission at D1 dopamine receptors.
Herz
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Department of Neuropharmacology, Max-Planck-Institut für Psychiatrie, Planegg-Martinsried, Federal Republic of Germany.
D000818:Animals; D001921:Brain / Q000378:metabolism*; D004723:Endorphins / Q000502:physiology; D006801:Humans; D009042:Motivation; D009294:Narcotics / Q000494:pharmacology*; D011954:Receptors, Dopamine; D017447:Receptors, Dopamine D1; D011957:Receptors, Opioid / Q000187:drug effects*
D004723:Endorphins; D009294:Narcotics; D011954:Receptors, Dopamine; D017447:Receptors, Dopamine D1; D011957:Receptors, Opioid