1.Evidence for different pharmacological targets for imidazoline compounds inhibiting settlement of the barnacle Balanus improvisus.
Dahlström M1, Lindgren F, Berntsson K, Sjögren M, Mårtensson LG, Jonsson PR, Elwing H. J Exp Zool A Comp Exp Biol. 2005 Jul 1;303(7):551-62.
We describe the effect of eight different imidazoline/guanidinium compounds on the settlement and metamorphosis of larvae of the barnacle Balanus improvisus. These agents were chosen on the basis of their similar pharmacological classification in vertebrates and their chemical similarity to medetomidine and clonidine, previously described as highly potent settlement inhibitors (nanomolar range). Seven of the tested compounds were found to inhibit settlement in a dose-dependent manner in concentrations ranging from 100 nM to 10 microM without any significant lethal effects. In vertebrate systems these substances have overlapping functions and interact with both alpha-adrenoceptors as well as imidazoline binding sites. Antagonizing experiments using the highly specific alpha(2)-antagonist methoxy-idazoxan or agmatine (the putative endogenous ligand at imidazoline receptors) were performed to discriminate between putative pharmacological mechanisms involved in the inhibition of cyprid settlement.
2.Synthesis and evaluation of PET probes for the imaging of I2 imidazoline receptors in peripheral tissues.
Kawamura K1, Yui J, Konno F, Yamasaki T, Hatori A, Wakizaka H, Fujinaga M, Kumata K, Yoshida Y, Ogawa M, Nengaki N, Yanamoto K, Fukumura T, Zhang MR. Nucl Med Biol. 2012 Jan;39(1):89-99. doi: 10.1016/j.nucmedbio.2011.06.001. Epub 2011 Aug 9.
INTRODUCTION: To explore the possible use of positron emission tomography (PET) probes for imaging of I(2)-imidazoline receptors (I(2)Rs) in peripheral tissues, we labeled two new I(2)R ligands, 2-[2-(o-tolyl)vinyl]-4,5-dihydro-1H-imidazole (K(i) for I(2)Rs, 3.7 nM) and 2-[2-(o-tolyl)ethyl]-4,5-dihydro-1H-imidazole (K(i) for I(2)Rs, 1.7 nM) with (11)C ([(11)C]metrazoline and [(11)C]TEIMD), respectively, and evaluated these ligands and the recently developed I(2)R ligand 2-[3-fluoro-[4-(11)C]tolyl]-4,5-dihydro-1H-imidazole ([(11)C]FTIMD) by in vivo studies.
3.Hyperphagic effect of novel compounds with high affinity for imidazoline I(2) binding sites.
Polidori C1, Gentili F, Pigini M, Quaglia W, Panocka I, Massi M. Eur J Pharmacol. 2000 Mar 24;392(1-2):41-9.
Previous studies have suggested that imidazoline I(2) receptors play a role in feeding control in rats. The effect of subcutaneous (s.c.) injections of four novel imidazoline I(2) ligands, 2-naphthalen-2yl-4,5-dihydro-1H-imidazole hydrochloride (benazoline), 2-styryl-4,5-dihydro-1H-imidazole oxalate (tracizoline), o-nitro-tracizoline and o-methyl-tracizoline (metrazoline) on food intake during the light phase was now evaluated in freely feeding male Wistar rats. Their effect was compared to that of idazoxan, a high-affinity ligand at imidazoline I(2) binding sites, but also a potent alpha(2)-adrenoceptor antagonist. Compared to idazoxan, metrazoline exhibits a higher pK(i) for imidazoline I(2) binding sites in rat liver, while the other compounds have a slightly lower pK(i); on the other hand, the novel compounds have much lower affinity than idazoxan at alpha(2)-adrenoceptors. Idazoxan stimulated drinking at a dose as low as 1 mg/kg, and evoked feeding at a higher dose (30 mg/kg).