176
|
Stark H, Orlova EV, Rinke-Appel J, Jünke N, Mueller F, Rodnina M, Wintermeyer W, Brimacombe R, van Heel M. Arrangement of tRNAs in pre- and posttranslocational ribosomes revealed by electron cryomicroscopy. Cell 1997; 88:19-28. [PMID: 9019401 DOI: 10.1016/s0092-8674(00)81854-1] [Citation(s) in RCA: 215] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The three-dimensional structure of the translating 70S E. coli ribosome is presented in its two main conformations: the pretranslocational and the posttranslocational states. Using electron cryomicroscopy and angular reconstitution, structures at 20 A resolution were obtained, which, when compared with our earlier reconstruction of "empty" ribosomes, showed densities corresponding to tRNA molecules--at the P and E sites for posttranslocational ribosomes and at the A and P sites for pretranslocational ribosomes. The P-site tRNA lies directly above the bridge connecting the two ribosomal subunits, with the A-site tRNA fitted snugly against it at an angle of approximately 50 degrees, toward the L7/L12 side of the ribosome. The E-site tRNA appears to lie between the side lobe of the 30S subunit and the L1 protuberance.
Collapse
|
177
|
Krause M, Rouleau A, Stark H, Garbarg M, Schwartz JC, Schunack W. Structure-activity relationships of novel azomethine prodrugs of the histamine H3-receptor agonist (R)-alpha-methylhistamine: from alkylaryl to substituted diaryl derivatives. DIE PHARMAZIE 1996; 51:720-6. [PMID: 8941938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
This study was performed on the basis of recently developed prodrugs of the histamine H3-receptor agonist (R)-alpha-methylhistamine (1) to determine structure-activity relationships of azomethine prodrugs of 1, in which the primary amine functionality is bioreversibly linked to aromatic ketones. Therefore, the pro-moiety was systematically altered from alkylaryl over benzylaryl to diaryl substitution. Those compounds that emerged to be stable enough during preparation were tested for their in vitro hydrolysis rates. Apparently, bulky alkyl residues were capable of preventing previously observed intramolecular cyclization, but the obtained azomethines 12a-c were far too unstable to serve as prodrugs. However, the benzylaryl imines 12d, e were stable compounds, but 12d decomposed too rapidly under in vitro conditions. Distinctly greater stability was provided by diaryl pro-moieties, even if strongly electron-withdrawing functionalities were introduced. Selected compounds were also tested in vivo following p.o. application to mice. Particularly the trifluoromethyl substituted imine 12i proved to be highly effective as stability and rate of conversion were well-balanced, so that brain penetration of 1 was strikingly facilitated. Thus 12i, a highly potent azomethine prodrug, may serve as an important pharmacological tool and, possibly, a therapeutic agent.
Collapse
|
178
|
Stark H, Lubensky TC. Multiple Light Scattering in Nematic Liquid Crystals. PHYSICAL REVIEW LETTERS 1996; 77:2229-2232. [PMID: 10061891 DOI: 10.1103/physrevlett.77.2229] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
|
179
|
Shucnack W, Hüls A, Purand K, Ligneau X, Garbarg M, Arrang JM, Schwartz JC, Stark H. Benzhydryl ethers prossessing combined histamine H3/H1-receptor antagonist activity. Eur J Pharm Sci 1996. [DOI: 10.1016/s0928-0987(97)86347-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
|
180
|
Stark H, Krause M, Rouleau A, Garbagh M, Ligneau X, Mantion C, Lavie P, Lecomte JM, Schwartz JC, Schunack W. Prodrug developments on histamine H3-receptors agonists. Eur J Pharm Sci 1996. [DOI: 10.1016/s0928-0987(97)86344-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
181
|
Stark H. [Especially elderly patients should have adequate chewing capacity. Interview by Dr. troph. Claudia Küpper]. FORTSCHRITTE DER MEDIZIN 1996; 114:16-7. [PMID: 8974958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
|
182
|
Hüls A, Purand K, Stark H, Reidemeister S, Ligneau X, Arrang JM, Schwartz JC, Schunack W. Novel histamine H3-receptor antagonists with benzyl ether structure or related moieties: synthesis and structure-activity relationships. Arch Pharm (Weinheim) 1996; 329:379-85. [PMID: 8915097 DOI: 10.1002/ardp.19963290802] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
In search of new histamine H3-receptor ligands sixteen ether derivatives of 3-(1H-imidazol-4-yl)propanol with benzylic partial structure or related moieties were prepared and investigated as H3-receptor antagonists. The new compounds belong to a general construction pattern developed by other histamine H3-receptor antagonists. Structural modifications were introduced in an attempt to optimize in vitro as well as in vivo activity. Structure-activity relationships of the new histamine H3-receptor antagonists are discussed. All ether derivatives showed in vitro activities in the nanomolar concentration range, but only compounds with bulky lipophilic residues were also active under in vivo conditions. The most active compound within this series was 3-(1H-imidazol-4-yl)propyl 1-naphthylmethyl ether (4n) presenting an ED50 of 3.2 +/- 1.9 mg/kg regarding enhancement of endogenous histamine in brain after p.o. administration to mice. Furthermore, comparison of the H3-receptor activities measured on synaptosomes of rat cerebral cortex and on guinea pig ileum gave a good correlation indicating homogeneity of central and peripheral H3-receptor test models. The most interesting compounds were also evaluated in functional in vitro assays with regard to their activities at histamine H1-, H2-, and muscarinic M3-receptors. The tested compounds showed very weak activities at these receptor subtypes demonstrating their H3-receptor selectivity.
Collapse
|
183
|
Hüls A, Purand K, Stark H, Ligneau X, Arrang JM, Schwartz JC, Schunack W. Diphenylmethyl ethers: synthesis and histamine H3-receptor antagonist in vitro and in vivo activity. Bioorg Med Chem Lett 1996. [DOI: 10.1016/0960-894x(96)00361-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
184
|
Krause M, Rouleau A, Stark H, Luger P, Garbarg M, Schwartz JC, Schunack W. New potent azomethine prodrugs of the histamine H3-receptor agonist (R)-alpha-methylhistamine containing a heteroarylphenyl partial structure. Arch Pharm (Weinheim) 1996; 329:209-15. [PMID: 8669985 DOI: 10.1002/ardp.19963290407] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The therapeutic value of histamine H3-receptor ligands is under current investigation. On the basis of recently described diary limine prodrugs of the histamine H3-receptor agonist (R)-alpha-methylhistamine (1) as a series of new azomethine prodrugs containing five- and six-membered heterocycles were synthesized and tested for their in vitro hydrolysis rates and in vivo activity after oral application. It was found that electron-deficient six-membered heterocycles drastically destabilized the imine double bond so that these prodrugs decomposed unsuitably fast. On the contrary, prodrugs containing five-membered heterocycles appeared to be highly effective for the CNS delivery of 1, and a remarkable correlation between chemical structure and pharmacokinetic profile was observed. Particularly (R)-4-fluoro-2-[[N-[1-(1H-imidazol-4-yl)-2-propyl]imino] (1H-pyrrol-2-yl)methyl]phenol (8c), the 2-furanyl analogue 8d, and its 3-furanyl isomer 8e proved to be equipotent to the most potent of recently described halogenated diaryl imine prodrugs of 1. However, in contrast to any other azomethine prodrug, 8c exhibited an incomparably long lasting delivery of 1 in the CNS and can thus be regarded as a 'retard' prodrug. Assuming that a therapeutic indication of histamine H3-receptor agonists will soon be established, these highly potent heteroarylphenyl azomethine prodrugs, which already serve as valuable pharmacological tools, may also become potential drugs in clinical use.
Collapse
|
185
|
Schlicker E, Kathmann M, Bitschnau H, Marr I, Reidemeister S, Stark H, Schunack W. Potencies of antagonists chemically related to iodoproxyfan at histamine H3 receptors in mouse brain cortex and guinea-pig ileum: evidence for H3 receptor heterogeneity? NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1996; 353:482-8. [PMID: 8740140 DOI: 10.1007/bf00169166] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
We determined the affinities of 16 newly synthesized H3 receptor antagonists in an H3 receptor binding assay and the potencies of 12 of these compounds at functional H3 receptors in the mouse brain cortex and guinea-pig ileum. The compounds differ from histamine in that the C-C-N side chain is replaced by a chain of the structure C-C-C-O. The two major aims of the study were (1) to investigate whether the two functional H3 receptors are pharmacologically different and (2) to derive structure-activity relationships. The specific binding of 3H-Na-methylhistamine to rat brain cortex membranes was monophasically displaced by each of the 16 compounds at pKi values ranging from 7.30 to 9.48. In superfused mouse brain cortex slices preincubated with 3H-noradrenaline, the electrically evoked tritium overflow was slightly decreased by iodoproxyfan and its deiodo analogue; this effect was counteracted by the H3 receptor antagonist clobenpropit. The other compounds did not affect the evoked tritium overflow by themselves. The concentration-response curve of histamine for its inhibitory effect on the electrically evoked tritium overflow was shifted to the right by the 12 compounds with apparent pA2 values ranging from 7.02 to 9.00. The 12 compounds also shifted to the right the concentration-response curve of R-a-methylhistamine for its inhibitory effect on the electrically induced contraction in guinea-pig ileum strips; the apparent pA2 values ranged from 5.97 to 9.00. Iodoproxyfan decreased the electrically induced contraction by itself and this effect was counteracted by the H3 receptor antagonist thioperamide. The apparent pA2 values in the two functional H3 receptor models showed a highly significant correlation (r = 0.882; P < 0.001). Highly significant correlations were also obtained when the pKi values of the compounds in the binding assay were compared to their apparent pA2 values in the mouse brain (r = 0.799; P < 0.004) and in the guinea-pig ileum (r = 0.851; P < 0.001). In each of the three experimental models, iodoproxyfan was the most potent compound; its deiodo analogue was less potent by more than 1.1 log units. The present results show that the compounds under study possess moderate to high affinity and/or (partial) H3 receptor antagonist potency. The two functional H3 receptors in the mouse brain cortex and the guinea-pig ileum may be slightly different; further studies are necessary to clarify whether this difference is due to H3 receptor heterogeneity, species variants or differences in the efficiency of receptor coupling. The marked difference in the affinity/potency between iodoproxyfan and its deiodo analogue may suggest that a highly lipophilic residue in that part of the molecule favours a high affinity/antagonistic potency at H3 receptors.
Collapse
|
186
|
Stark H, Purand K, Hüls A, Ligneau X, Garbarg M, Schwartz JC, Schunack W. [125I]iodoproxyfan and related compounds: a reversible radioligand and novel classes of antagonists with high affinity and selectivity for the histamine H3 receptor. J Med Chem 1996; 39:1220-6. [PMID: 8632428 DOI: 10.1021/jm9504767] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The synthesis and biological evaluation of new histamine H3 receptor antagonists with an iodinated aryl partial structure are described as part of an extensive research program to find model compounds for the development of a new radioligand with high H3 receptor affinity and specific activity. All compounds were tested for their H3 receptor antagonist activity in a [3H]-histamine-release assay with synaptosomes from rat cerebral cortex. The new leads with potent H3 receptor antagonist activity belong to a series of derivatives of 3-(1H-imidazol-4-yl)propanol with carbamate (4-7), ester (8-16), and ether (17-22) as functional groups. Structure-activity relationships are discussed. The most active compound in the functional test (-log Ki = 8.3) and in binding studies with [3H]-(R)-alpha-methylhistamine on rat cerebral cortex (-log Ki = 9.0) in vitro was 3-(1H-imidazol-4-yl)propyl (4-iodophenyl)methyl ether (iodoproxyfan, 19) exhibiting no central H3 receptor antagonist activity in vivo. The potency of iodoproxyfan is more than 300 times lower at H1, H2, alpha1, alpha2, beta1, 5-HT2A, 5-HT3, and M3 receptors than at histamine H3 receptors. Because of the high potency and selectivity of 19, this compound has also been prepared in the [125I]-iodinated form by a nucleophilic halogen exchange reaction using the corresponding bromo derivative 22 as a precursor. The newly prepared [125I]iodoproxyfan (23) possesses advantageous pharmacological properties and fulfills all criteria of a useful radioligand.
Collapse
|
187
|
Stark H, Purand K, Ligneau X, Rouleau A, Arrang JM, Garbarg M, Schwartz JC, Schunack W. Novel carbamates as potent histamine H3 receptor antagonists with high in vitro and oral in vivo activity. J Med Chem 1996; 39:1157-63. [PMID: 8676353 DOI: 10.1021/jm9507688] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The known histamine H3 receptor antagonists burimamide, thioperamide, clobenpropit, and a related homohistamine thioamide derivative were taken as templates in search for new leads. Novel histamine H3 receptor antagonists structurally described as carbamate derivatives of 3-(1H-imidazol-4-yl)propanol were prepared in high yields by treatment of the alcohol with corresponding isocyanates or carbamoyl chlorides and investigated for their H3 receptor antagonist activity. Different chain lengths and various substituents possessing different electronic and steric parameters were introduced and structure-activity relationships established. In different functional tests, the new antagonists showed high H3 receptor antagonist potencies in vitro (-log Ki values of 6.4-8.4) at synaptosomes of rat cerebral cortex and low activities at histamine H1 and H2 receptor subtypes. They were also screened for their central in vivo activity in mice after peroral administration. The most promising compounds (2, 16, 19) showed ED(50) values of about 1-2 mg/kg and thus are potential drugs for the therapy of H3 receptor dependent diseases. Some of the novel carbamate derivatives are H3 receptor selective compounds with high in vitro and in vivo activity.
Collapse
|
188
|
Lubensky TC, Stark H. Theory of a critical point in the blue-phase-III-isotropic phase diagram. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 1996; 53:714-720. [PMID: 9964304 DOI: 10.1103/physreve.53.714] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/01/2023]
|
189
|
Krause M, Rouleau A, Stark H, Luger P, Lipp R, Garbarg M, Schwart JC, Schunack W. Synthesis, X-ray crystallography, and pharmacokinetics of novel azomethine prodrugs of (R)-alpha-methylhistamine: highly potent and selective histamine H3 receptor agonists. J Med Chem 1995; 38:4070-9. [PMID: 7562942 DOI: 10.1021/jm00020a022] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Since various neuroregulatory functions of the histamine H3 receptor have been proved during the last few years, the H3 receptor is of current interest. Azomethine derivatives of the highly potent histamine H3 receptor agonist (R)-alpha-methylhistamine (1) were prepared as lipophilic prodrugs to improve the bioavailability of the hydrophilic drug, particularly its entry into the brain. Additionally, azomethine derivatization provides protection against histamine methyltransferase, the major metabolizing enzyme in man, and thus efficiently enhances the bioavailability of 1. The molecular conformations of (R)-2(-)[[N(-)[1-(1H-imidazol-4-yl)-2-propyl]- imino]phenylmethyl]phenol (9a) and (R)-4-fluoro-2(-)[[N(-)[1-(1H-imidazol-4-yl)-2-propyl[imino]- (4-chlorophenyl)methyl]phenol (9p) were determined by X-ray structure analysis. An intramolecular hydrogen bond which is essential for the stability of these azomethines was thereby confirmed. Moreover, the pharmacokinetic parameters of the prodrugs were investigated in vitro as well as in vivo. The halogenated azomethines have an effect following peroral administration in mice, and some of them seem to be highly potent for the central nervous system (CNS) delivery of 1. At present the most potent prodrug of 1 is (R)-4-chloro-2(-)[[N(-)[1-(1H-imidazol-4-yl)-2-propyl]imino](4- chlorophenyl)methyl]phenol (9q), reaching by far the highest CNS level of 1 (Cmax = 71 ng/g). Prodrugs of this type are not only valuable pharmacological tools but may also become H3 histaminergic drugs for therapeutic use.
Collapse
|
190
|
Stark H, Mueller F, Orlova EV, Schatz M, Dube P, Erdemir T, Zemlin F, Brimacombe R, van Heel M. The 70S Escherichia coli ribosome at 23 A resolution: fitting the ribosomal RNA. Structure 1995; 3:815-21. [PMID: 7582898 DOI: 10.1016/s0969-2126(01)00216-7] [Citation(s) in RCA: 197] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
BACKGROUND The ribosome--essential for protein synthesis in all organisms--has been an evasive target for structural studies. The best available structures for the 70S Escherichia coli ribosome or its 30S and 50S subunits are based on electron microscopical tilt experiments and are limited in resolution to 28-55 A. The angular reconstitution approach, which exploits the random orientations of particles within a vitreous ice matrix, can be used in conjunction with cryo-electron microscopy to yield a higher-resolution structure. RESULTS Our 23 A resolution map of the 70S ribosome elucidates many structural details, such as an extensive system of channels within the 50S subunit and an intersubunit gap ideally shaped to accommodate two transfer RNA molecules. The resolution achieved is sufficient to allow the preliminary fitting of double-helical regions of an earlier three-dimensional ribosomal RNA model. CONCLUSIONS Although we are still a long way from attaining an atomic-resolution structure of the ribosome, cryo-electron microscopy, in combination with angular reconstitution, is likely to yield three-dimensional maps with gradually increasing resolution. As exemplified by our current 23 A reconstruction, these maps will lead to progressive refinement of models of the ribosomal RNA.
Collapse
|
191
|
Lewit N, Batino S, Groisman GM, Stark H, Bronshtein M. Early prenatal diagnosis of Larsen's syndrome by transvaginal sonography. JOURNAL OF ULTRASOUND IN MEDICINE : OFFICIAL JOURNAL OF THE AMERICAN INSTITUTE OF ULTRASOUND IN MEDICINE 1995; 14:627-629. [PMID: 7474064 DOI: 10.7863/jum.1995.14.8.627] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
|
192
|
Kieć-Kononowicz K, Ligneau X, Stark H, Schwartz JC, Schunack W. Azines and diazines as potential histamine H3-receptor antagonists. Arch Pharm (Weinheim) 1995; 328:445-50. [PMID: 7611840 DOI: 10.1002/ardp.19953280509] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
In search of structure-activity relationships among histamine H3-receptor antagonists the imidazole ring of known H3-receptor antagonists was replaced by different heteroaromatic ring systems. Thus, azines and diazines with ether (6-13) and carbamate (15-24) moieties as functional groups were synthesized. The obtained compounds did not show significant H3-receptor antagonist activity in vitro (rat brain cortex) or in vivo (mice brain). The new compounds were also screened for H1-receptor antagonist activity on the isolated guinea-pig ileum and for H2-receptor antagonist activity on the isolated spontaneously beating guinea-pig right atrium. The substances showed only weak antagonistic activity at both histamine receptors, H1 and H2.
Collapse
|
193
|
Stark H, Trebin HR. Hydrodynamical modes and light scattering in the liquid-crystalline cubic blue phases. I. Elastic theory. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 1995; 51:2316-2325. [PMID: 9962893 DOI: 10.1103/physreve.51.2316] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
194
|
Stark H, Trebin HR. Hydrodynamical modes and light scattering in the liquid-crystalline cubic blue phases. II. Dynamic theory. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 1995; 51:2326-2340. [PMID: 9962894 DOI: 10.1103/physreve.51.2326] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
|
195
|
Lipp R, Stark H, Arrang JM, Garbarg M, Schwartz JC, Schunack W. Synthesis and histamine H3-receptor agonist activity of mono- and dialkyl-substituted histamine derivatives. Eur J Med Chem 1995. [DOI: 10.1016/0223-5234(96)88228-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
196
|
Stark H, Krause M, Arrang JM, Ligneau X, Schwartz JC, Schunack W. Unsymmetrically substituted guanidines as potent histamine H3-receptor antagonists. Bioorg Med Chem Lett 1994. [DOI: 10.1016/s0960-894x(01)80838-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
197
|
Ligneau X, Garbarg M, Vizuete ML, Diaz J, Purand K, Stark H, Schunack W, Schwartz JC. [125I]iodoproxyfan, a new antagonist to label and visualize cerebral histamine H3 receptors. J Pharmacol Exp Ther 1994; 271:452-9. [PMID: 7965746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Iodoproxyfan, i.e., 3-(1H-imidazol-4-yl)propyl-(4-iodophenyl)-methyl ether, is a novel potent and selective histamine H3 receptor antagonist. [125I]Iodoproxyfan binding to membranes of the rat striatum was reversible and saturable. Specific binding defined with 1 microM (R)-alpha-methylhistamine corresponded to 65% of the total at 30 pM. Scatchard analysis indicated a Kd of 65 pM and maximal binding capacity of 78 fmol/mg of protein. The specificity of [125I]Iodoproxyfan binding to H3 receptors was demonstrated by its pharmacological profile. A series of H3 receptor agonists inhibited [125I]iodoproxyfan binding with a similar maximal effect and with the expected order of potency and stereoselectivity ratio. H3 receptor antagonists inhibited the specific binding with the expected Ki values. In the presence of guanylnucleotides, 40% of sites exhibited a approximately 40-fold lower affinity for histamine, indicating that the H3 receptor belongs to the superfamily of G protein-coupled receptors and revealing the existence of two populations of sites. Well contrasted autoradiographic pictures of total [125I]iodoproxyfan binding to sections of the rat brain were obtained in a short time and over a low nonspecific binding. The heterogenous distribution of H3 receptors with high labeling of anterior cerebral cortex, ventral striatum and other limbic areas was confirmed. In addition, a clearly distinguishable laminated pattern of labeling was evidenced in the cerebral cortex and hippocampal formation. Hence, this new probe should be useful for sensitive assay and localization of the H3 receptor.
Collapse
|
198
|
Hüls A, Purand K, Stark H, Ligneau X, Garbarg M, Schwartz JC, Schunack W. P84 novel potent histamine H3-receptor antagonists. Eur J Pharm Sci 1994. [DOI: 10.1016/0928-0987(94)90257-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
199
|
Kathmann M, Schlicker E, Reidemeister S, Stark H, Schunack W. P86 novel histamine H3-receptor antagonists: Affinities in an H3-receptor binding assay and potencies in two functional H3-receptor models. Eur J Pharm Sci 1994. [DOI: 10.1016/0928-0987(94)90259-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
200
|
Schlicker E, Kathmann M, Reidemeister S, Stark H, Schunack W. Novel histamine H3 receptor antagonists: affinities in an H3 receptor binding assay and potencies in two functional H3 receptor models. Br J Pharmacol 1994; 112:1043-8. [PMID: 7952862 PMCID: PMC1910257 DOI: 10.1111/j.1476-5381.1994.tb13188.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
1. We determined the affinities of ten novel H3 receptor antagonists in an H3 receptor binding assay and their potencies in two functional H3 receptor models. The novel compounds differ from histamine in that the aminoethyl side chain is replaced by a propyl or butyl chain linked to a polar group (amide, thioamide, ester, guanidine, guanidine ester or urea) which, in turn, is connected to a hexocyclic ring or to an alicyclic ring-containing alkyl residue [corrected]. 2. The specific binding of [3H]-N alpha-methylhistamine to rat brain cortex membranes was monophasically displaced by each of the ten compounds at pKi values ranging from 7.56 to 8.68. 3. Inhibition by histamine of the electrically evoked tritium overflow from mouse brain cortex slices preincubated with [3H]-noradrenaline was antagonized by the ten compounds and the concentration-response curve was shifted to the right with apparent pA2 values ranging from 7.07 to 9.20. 4. The electrically induced contraction in guinea-pig ileum strips (which was abolished by atropine) was inhibited by the H3 receptor agonists R-(-)-alpha-methylhistamine (pEC50 7.76), N alpha-methylhistamine (7.90) and imetit (8.18). The concentration-response curve of R-(-)-alpha-methylhistamine was shifted to the right by thioperamide (apparent pA2 8.79) and by the ten novel compounds (range of pA2 values 6.64-8.81). 5. The affinities and potencies were compared by linear regression analysis. This analysis was extended to thioperamide, the standard H3 receptor antagonist, which is also capable of differentiating between H3A and H3B sites. Comparison of the apparent pA2 values in the two functional H3 receptor models yielded a regression coefficient of 0.77 (P<0.02). When the pA2 of the drugs in the mouse brain cortex were compared to the pXj for H3 sites (ten novel compounds) and for H3A sites (thioperamide), a significant correlation (r = 0.87; P<0.001) was obtained. There was, however, no significant correlation when the pKi of thioperamide for H3B sites was used instead (r = 0.52). In a similar manner, comparison of the pA2 in the guinea-pig ileum with the pKi in the binding assay yielded a significant correlation(r = 0.70, P <0.05) only when the pKi of thioperamide for H3A sites was used but not when its pKi forH3B sites was considered (r = 0.17, NS).6 On the basis of these results, structure-activity relationships for the novel H3 receptor antagonists,and the nature of the H3 receptors in the guinea-pig ileum and mouse brain, are considered.
Collapse
|