Activation of MORs in the VTA induces changes on cFos expression in different projecting regions: Effect of inflammatory pain

Publication date: Available online 13 August 2019Source: Neurochemistry InternationalAuthor(s): Yolanda Campos-Jurado, Marta Igual-López, Félix Padilla, Teodoro Zornoza, Luis Granero, Ana Polache, Carmen Agustín-Pavón, Lucía HipólitoAbstractChronic pain is a worldwide major health problem and many pain-suffering patients are under opioid based therapy. Epidemiological data show that pain intensity correlates with the risk of misuse of prescription opioids, and other drugs of abuse including alcohol. This increased vulnerability to suffer Substance Use Disorders could be, in part, caused by functional changes that occur over the mesocorticolimbic system, a brain pathway involved in reward processing and addiction. Previous data in rats revealed that inflammatory pain desensitizes mu opioid receptors (MORs) in the ventral tegmental area (VTA). As a consequence, pain alters dopamine release in the nucleus accumbens (NAc) derived from MOR activation in the VTA and also increases intake of high doses of heroine. Given that the VTA neurons target different brain regions, in the present study we first analyzed changes induced by inflammatory pain in the MOR dependent activation pattern of the main VTA projecting areas. To do that, we administered two doses (7 or 14 ng) of DAMGO (MORs agonist) or artificial cerebrospinal fluid (aCSF) focally into the VTA of rats and measured the activation in projection areas by cFos immunohistochemistry. Our results show that focal injection...
Source: Neurochemistry International - Category: Neuroscience Source Type: research