ORIGINAL ARTICLE Regulation of opioid gene expression in the rat brainstem by 3,4-methylenedioxymethamphetamine (MDMA): role of serotonin and involvement of CREB and ERK cascade Manuela Di Benedetto & Sussy del Carmen Bastías Candia & Claudio D’Addario & Elena Elettra Porticella & Chiara Cavina & Sanzio Candeletti & Patrizia Romualdi Received: 8 June 2010 / Accepted: 1 December 2010 / Published online: 23 December 2010 # Springer-Verlag 2010 Abstract The amphetamine analogue 3,4-methylendioxy- metamphetamine (MDMA, Ecstasy) causes complex adap- tations at the molecular and cellular levels altering the activity of different brain neurotransmitters. The present study aims to verify the effects of single and repeated injections of MDMA on dynorphin and nociceptin systems gene regulation in the brainstem, an area rich in neurons containing serotonin. Both acute and chronic (twice a day for 7 days) MDMA (8 mg/kg) induced a marked increase in prodynorphin mRNA levels as well as in cAMP response element-binding protein (CREB) and extracellular signal- regulated kinase-1/2 (ERK1/2) phosphorylation, without causing any effect on kappa opioid receptor or nociceptin system (both pronociceptin and its receptor) genes expres- sion, in this brain region. The blockade of 5HT1/5HT2 receptors by methysergide abolished the acute MDMA- induced increase in prodynorphin. Moreover, the concom- itant chronic administration of both methysergide and MDMA (7 days) induced a significant increase in all the dynorphin or nociceptin system genes expression and in CREB and ERK phosphorylation. Our data suggest the involvement of dynorphin in the effects evoked by MDMA in the brainstem, possibly via CREB and ERK1/2 cascade activation, since the ERK inhibitor PD98059 prevented the MDMA-induced prodynorphin gene expression, and, acute- ly, also through the involvement of serotoninergic mecha- nisms. Chronically, it is also possible to hypothesize a general inhibitor role of serotonin in the effects evoked by MDMA. Moreover, these findings strengthen the hypothe- sis, already proposed, of a neuroprotective role for both CREB and dynorphin. Keywords Brainstem . CREB . MAP/ERK kinases . MDMA . Opioid system Introduction 3,4-Methylendioxymetamphetamine (MDMA, Ecstasy) is an amphetamine derivative with increasing popularity as a recreational drug. Several studies have shown that MDMA stimulates the release and exchange of serotonin (5-HT) from neurons, inhibits its reuptake and binds to 5-HT transporter (SERT; Rudnick and Wall 1992; Gudelsky and Nash 1996), but the molecular effects occurring after these events have not been elucidated yet. Many studies demonstrated the involvement of the endogenous opioid system in some of the behavioural effects induced by MDMA. In fact, among the non-selective opioid antago- nists, naloxone blocks the hyperlocomotion produced by MDMA in mice (Compan et al. 2003), and naltrexone attenuates MDMA ’ s ability to produce conditioned place preference in rats (Bilsky et al. 1991). In addition, naltrindole, the selective delta-opioid antagonist, blocks the enhancement induced by MDMA on reinforcing brain stimulation (Reid et al. 1996). Exposure to various drugs of abuse, including MDMA, and acting through different neuronal mechanisms, evokes long-term changes in the gene expression of the opioid peptides (Adams et al. 2005; Daunais et al. 1993; Hurd et al. 1992; Mathieu-Kia and Besson 1998; Romualdi et al. Manuela Di Benedetto and Sussy del Carmen Bastías Candia equally contributed to this paper. M. Di Benedetto (*) : S. Bastías Candia : C. D’Addario : E. E. Porticella : C. Cavina : S. Candeletti : P. Romualdi Department of Pharmacology, Alma Mater Studiorum-University of Bologna, via Irnerio 48, 40126 Bologna, Italy e-mail: manuela.dibenedetto@unibo.it Naunyn-Schmied Arch Pharmacol (2011) 383:169–178 DOI 10.1007/s00210-010-0587-5