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Genetic and environmental factors interact to determine the individual vulnerability to develop ethanol dependence. The neurobiological mechanisms underlying these processes are not fully understood. Endogenous opioid peptides have been suggested to contribute. Brain opioids mediate ethanol reward and reinforcement via actions on the mesocorticolimbic dopamine system. This thesis focuses on environmental factors and investigates the impact of the early-life environment on adult voluntary ethanol consumption. The possible involvement of opioid peptides in environmental influences on adult ethanol consumption was examined using an experimental animal model. Maternal separation with short 15 min separations (MS15) was used to simulate a safe environment whereas prolonged 360 min separations (MS360) simulated an unsafe environment. Control rats were subjected to normal animal facility rearing (AFR). The separations were performed daily from postnatal day 1 to 21. Long-term ethanol consumption was registered using a two-bottle or a four-bottle free-choice paradigm in adult male and female ethanol-preferring AA (Alko, Alcohol), ethanol-avoiding ANA (Alko, Non-Alcohol) and non-preferring Wistar rats. In addition, analyses of immunoreactive Met-enkephalin-Arg6Phe7 (MEAP), dynorphin B (DYNB) and nociceptin/orphanin FQ (N/OFQ) peptide levels were performed after maternal separation as well as after voluntary ethanol drinking. In male rats, MS15 was related to lower ethanol consumption and these rats preferred lower concentrations, whereas MS360 was associated with an increased risk for higher consumption and/or preference for higher ethanol concentrations. Differences in basal opioid levels were observed in MS15 and MS360 rats. Furthermore, the ethanol-induced effects on opioid peptides in adults were dependent on the early environment. Female rats, on the other hand, were less affected or unaffected by maternal separation both in terms of ethanol consumption and neurobiological effects. Taken together, voluntary ethanol drinking, preference for low or high ethanol concentrations and opioid peptides in brain areas related to reward and reinforcement, motivation and stress were influenced by postnatal maternal separation in a sex dependent manner. The early environment thus had profound impact on the adult brain and the individual propensity for high ethanol drinking. A deranged endogenous opioid system contributed to these effects and may act as a mediator for long-term environmental influence on voluntary ethanol consumption.

Interactions between peptides and biological lipid membranes play a crucial role in many cellular processes such as in the mechanism behind Alzheimer’s disease where amyloid-beta peptide (Abeta)is thought to be a key component. The initial step of binding between a surface active peptide and its target membrane or membrane receptor can involve a non specific electrostatic association where positively charged amino acid residues and a negatively charged membrane surface interact. Here, the use of high resolution MAS NMR provides a highly sensitive and non perturbing way of studying the electrostatic potential present at lipid membrane surfaces and the changes resulting from the association of peptides. The interaction between pharmacologically relevant peptides and lipid membranes can also involve incorporation of the peptide into the membrane core and by complementing the NMR approach with differential scanning calorimetry (DSC) the hydrophobic incorporation can be studied in a non invasive way. By using 14N MAS NMR on biological lipid systems for the first time, in addition to 31P, 2H NMR and differential scanning calorimetry (DSC), gives a full picture of the changes all along the phospholipid following interactions at the membrane interface region. Being able to monitor the full length of the phospholipid enables us to differentiate between interactions related to either membrane surface association or hydrophobic core incorporation. This approach was used to establish that the interaction between nociceptin and negatively charged lipid membranes is electrostatic and hence that nociceptin can initially associate with a membrane surface before binding to its receptor. Also, it was found that Abeta can interact with phospholipid membranes via two types of interactions with fundamentally adverse effects. The results reveal that Abeta can associate with the surface of a neuronal membrane promoting accelerated aggregation of the peptide leading to neuronal apoptotic cell death. Furthermore it is also shown that Abeta can anchor itself into the membrane and suppress the neurotoxic aggregation of Abeta.