A shared neuroimmunological mechanism for drugs of addiction?

Abstract

The article by Saurer et al., 2004 Saurer T.B. Carrigan K.A. Ijames S.G. Lysle D.T. Morphine-induced alterations of immune status are blocked by the dopamine D2-like receptor agonist 7-OH-DPAT. J. Neuroimmunol. 2004; 148: 54-62 Abstract Full Text Full Text PDF PubMed Scopus (26) Google Scholar in this issue provides compelling evidence that site-specific microinjection of morphine activates dopamine-receptive neurons in the shell of the nucleus accumbens that in turn induces suppression of splenic NK cell activity. It has been appreciated in the addiction research literature for some time that the reinforcing or rewarding effects of various addictive drugs share a common mechanism of action via activation of the limbic projection of dopaminergic neurons from ventral tegmental area (VTA) to the nucleus accumbens ( Nestler, 2005 Nestler E.J. Is there a common molecular pathway for addiction?. Nat. Neurosci. 2005; 8: 1445-1449 Crossref PubMed Scopus (1007) Google Scholar ). Though it had been reported that administration of cocaine and amphetamine—drugs with well established addictive effects attributable to their pharmacological actions on dopamine release in the nucleus accumbens—can suppress splenic NK activity in animals ( Nunez-Iglesias et al., 1996 Nunez-Iglesias M.J. Castro-Bolano C. Losada C. Pereiro-Raposo M.D. Riveiro P. Sanchez-Sebio P. Mayan-Santos J.M. Rey-Mendez M. Freire-Garabal M. Effects of amphetamine on cell mediated immune response in mice. Life Sci. 1996; 58: 29-33 PubMed Google Scholar , Pacifici et al., 2003 Pacifici R. Fiaschi A.I. Micheli L. Centini F. Giorgi G. Zuccaro P. Pichini S. Di Carlo S. Bacosi A. Cerretani D. Immunosuppression and oxidative stress induced by acute and chronic exposure to cocaine in rat. Int. Immunopharmacol. 2003; 3: 581-592 Crossref PubMed Scopus (49) Google Scholar ), the best available evidence indicated that the immunosuppressive actions of morphine and related opioids were mediated by other brain mechanisms. The study by Sauer and colleagues in Dr. Lysle's laboratory provides intriguing and important new data that suggests that different classes of addictive drugs induce suppression of NK cell activity by modulating nucleus accumbens dopamine. As the authors propose, this work is important as it suggests that activation of D1-like dopamine receptors in the shell of the nucleus accumbens may activate a common central circuitry that induces NK cell suppression in the spleen. Suppression of natural killer cell activity by morphine is mediated by the nucleus accumbens shellJournal of NeuroimmunologyVol. 173Issues 1-2PreviewDespite a wealth of data indicating that morphine modulates immune status by acting at μ-opioid receptors in the brain, there is little known about how the opioid system interacts with other neurotransmitter systems to modulate specific immune parameters. The aim of the present study was to investigate whether dopaminergic projections to the nucleus accumbens are involved in morphine-induced suppression of splenic natural killer (NK) cell activity. The results indicate that administration of the dopamine D1 antagonist SCH-23390 into the nucleus accumbens shell, but not core, blocked morphine's suppressive effect on NK activity in male Lewis rats. Full-Text PDF