Diss. (sammanfattning) Stockholm : Karolinska institutet, 2006. / Härtill 4 uppsatser.

The interaction of a diverse set of opioid alkaloids and peptides with various opioid receptors has been examined using biochemical and pharmacological techniques. Structural information on the compounds was obtained from single crystal X-ray diffraction and nuclear magnetic resonance studies, and modelled by computational methods. The introduction of a dithiocarbazate moiety into the 7a-position of a bridged thebaine was shown to afford a degree of μ selectivity in this class of nonselective compounds. X-ray diffraction analysis of this compound and comparison with the structure of [Met5]enkephalin showed the importance of the sulphydryl moiety. The conformation of [Leu5]enkephalin, in which the amino acid methionine is replaced by leucine, at the same receptor is unlikely to be similar. A series of morphinan derivatives which had been developed as μ-antagonists were evaluated. Substitution patterns of the morphinan ring nucleus and their effect upon activity were examined. X-ray analysis of several key compounds was performed. Unexpectedly a 3-hydroxymorphinan-6-one analogue showed an ability to differentiate apparently similar opioid Kreceptors. The implications in terms of K-receptor subtypes are discussed. The opioid receptor binding characteristics of structurally diverse K-receptor ligands were examined in two different buffer systems. Electrostatic modelling of the K-ligands, based upon crystal structure coordinates, was performed. From electrostatic potential maps a requirement for ligands acting at Kreceptors is postulated. Solution conformations of the endogenous K-ligand, dynorphin A(1-8), were determined by nuclear magnetic resonance studies and compared with the wo preferring [Leu5]enkephalin. Models were proposed based upon dihedral angles determined from HCtl-NH coupling constants, amide proton-deuteron exchange and amide proton temperature coefficient data. Candidate conformations were shown to be stable under dynamic simulation conditions. Electrostatic modelling of a chosen dynorphin An-8) conformation gave results comparable with the observed electrostatic model of the K-ligands. The proposed model is discussed in terms of its suitability as a retro-model for the active site ofthe K-opioid receptor.

It has recently been discovered that the effect of morphine can significantly reduce the tissue damage that occurs during myocardial ischemia. The molecular mechanisms by which morphine acts on the heart are still little understood. The aim of this thesis was to monitor the effect of chronic 27-day and 10-day administration of low (1 mg/kg/day) and high (10 mg/kg/ day) doses of morphine on the expression of selected G-protein-coupled receptors (GPCR) and on the expression and activity of adenylyl cyclase (AC). Chronic (27 days) morphine treatment reduced the expression of к-opioids receptors, but 10-day morphine exposure did not influence the expression of these receptors. Assessment of β1- and β2-AR by immunoblot technique did not show any significant change in the expression, but the more accurate determination of β-AR expression using the saturation binding studies revealed that 27-day treatment with high doses of morphine appreciable increased the total number of these receptors. Administration of high doses of morphine led to marked up-regulation of adenylyl cyclase (AC) isoforms V/VI, and the amount of AC decreased proportionally with the time of discontinuation of morphine administration. Low doses of morphine up- regulated AC only during 27-day administration. Chronic morphine exposure did...