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Biomedical subjects

A Lucacchini

Publications and source records attributed to A Lucacchini.

At least 109 records · Page 6Linked to original sources
PubMed1994

2-Aryl-8-azaadenosines: structure-activity relationships in the binding with A1 and A2 receptors. A comparison with the corresponding 9-benzyl-8-azaadenines. III.

Several title compounds were assayed to determine their relative affinity towards the adenosine receptors. Selectivity ratios (SR) showed a prevalent A1 affinity. The comparison with the selectivity ratios of the corresponding 9-benzyl-8-azaadenines and the comparison between the affinity constant values (K1) for each receptor of the two series, were performed. The results led us to conclude that A1 receptors are characterized by more different arrangements which regard especially to 9-benzyl-8-azaadenines.

Adenine↗
PubMed1994

N(6)-substituted 2-phenyl-9-benzyl-8-azaadenines. Affinity for adenosine A1 and A2 receptors. A comparison with 2-N-butyl analogous derivatives. V.

The title compounds were prepared to evaluate their affinity towards adenosine A1 and A2 receptors. Some 2-phenyl-N(6)-substituted-8-azadenines showed good binding properties and good A1 selectivity. The biological results allow us to confirm the presence in A1 receptors of a third lipophilic pocket, able to receive the substituent on N(9), and to evince increased affinity when a phenyl group on C(2) substitutes an n-butyl group. These affinity differences between analogous 2-n-butyl and 2-phenyl derivatives indicate that they arrange themselves within A1 receptors in a similar manner and suggest that this receptor is able to arrange 8-azaadenines, bearing three lipophilic substituents, in two different ways.

Adenine↗
PubMed1994

Studies on annelated 1,4-benzothiazines and 1,5-benzothiazepines. VIII-Synthesis and inhibition of benzodiazepine receptor binding of some derivatives of triazino[3,4-c]-1,4-benzothiazine and triazino[3,4-d]-1,5-benzothiazepine, two new heterocyclic ring systems.

Several series of triazino[3,4-c]-1,4-benzothiazines and triazino[3,4-d]-1,5-benzothiazepines were synthesized. Tentative syntheses performed to obtain 5H-as-triazino[3,4-c]-1,4-benzothiazin-1,2-diones and 5,6-dihydro-as-triazino[3,4-d]-1,5-benzothiazepin-1,2-diones gave rise to s-triazolo derivatives. Only in one case was the reaction successful, affording the 3,5-dihydro-as-triazino[3,4-c]-1,4-benzothiazin-1,2-dione 9a. All the final compounds were tested for their ability to displace [3H]flunitrazepam from bovine brain membranes.

Animals↗
PubMed1994

1,2,3-triazole[4,5-d]pyridazines. III--Synthesis of new 4-amino derivatives and their affinity toward adenosine receptors.

This paper describes the preparation and adenosine receptor binding of new 1-benzyl-4-aminosubstituted-1,2,3-triazole[4,5-d]pyridazines and of other 4-aminoderivatives bearing in the 1 position other neutral substituents. The synthetic procedures consist of nucleophilic displacement reactions from the 4-chloro derivative (procedure 1), of displacement of O-sililated intermediates (procedure 2) and of the use of phosphorus pentoxide-triethylamine hydrochloride reagent (procedure 3). The A1 adenosine receptor affinity is confirmed for the 1-benzyl substituted compounds bearing in the 4 position an arylamino or cycloalkylamino group. In addition, the compound obtained by reaction with racemic alpha-methylbenzylamine shows an interesting A1 activity, unlike the 4-benzylamino derivative.

Amines↗
PubMed1994

Age-related changes in peripheral benzodiazepine receptors of human platelets.

Using 3H-PK 11195 as radioligand, the number and affinity of peripheral benzodiazepine receptors in platelets of 15 elderly healthy subjects were compared to those of 15 young subjects. The results showed that the dissociation constant (Kd) was significantly higher in the elderly than in the young subjects, while the density of binding sites did not differ. These findings suggest that the age-related changes in peripheral benzodiazepine receptors may be coupled with secondary changes in their hypothesized functions.

Adult↗
PubMed1993

Regulation of agonist binding to A2A adenosine receptors: effects of guanine nucleotides (GDP[S] and GTP[S]) and Mg2+ ion.

Adenosine acts as a neuromodulator through at least two receptor subtypes, A1 and A2. A2 receptors have been further divided into A2A (high agonist affinity) and A2B (low agonist affinity) receptors. Both A1 and A2 receptors belong to the superfamily of guanine nucleotide-binding regulatory protein (G protein)-coupled receptors. A Gs protein couples the A2A receptor to the activation of adenylyl cyclase. In order to elucidate the mechanism of coupling between the A2A receptor and Gs, we studied the modulation by guanine nucleotides and divalent cations of agonist binding to the A2A receptor in rat striatal membranes, using [3H]CGS 21680 as a selective high-affinity agonist. We demonstrated that in rat striatal membranes agonist binding to A2A receptors was modulated by guanine nucleotides. Both GDP and GTP inhibited [3H]CGS 21680 binding to rat striatal membranes with about equal potency. The nonhydrolyzable analogs, GDP[S] and GTP[S], were equipotent inhibitors and approx. 100-times more potent than GDP and GTP. Data from competition studies with labeled and unlabeled CGS 21680 when analyzed by nonlinear regression demonstrated the presence of two binding sites in rat striatal membranes with mean values for KD of 5.6 and 343 nM and Bmax of 200 and 942 fmol/mg protein. The high-affinity binding site has the characteristics of the A2A receptor. In the presence both of (0.1 mM) GDP[S] and GTP[S], the KD values for the high-affinity site were increased severalfold, whereas the low-affinity site was no longer detected in filtration assays. Dissociation studies revealed monophasic dissociation curves both in the absence and presence of 0.1 mM GDP[S]. However the K-1 value increased in the presence of guanine nucleotide. We also showed that in bovine striatal membranes agonist binding to A2A receptors was modestly modulated by guanine nucleotides, suggesting differences of receptor Gs-protein-coupling a mechanism in different species. Divalent cations often increase agonist binding to different receptors, whereas Mg2+ ions play a role in regulating the initial steps of G-protein activation. We investigated the effects of divalent cations on [3H]CGS 21680 binding to the A2A receptor and determined the requirement of these cations to obtain the modulation of binding by guanine nucleotides. We found that millimolar concentrations of divalent cations were required to obtain an effective interaction between the A2A receptor and Gs. The high-affinity binding of [3H]CGS 21680 to the A2A receptor in rat striatal membranes was dependent on the presence of Mg2+ ions.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Studies on specific inhibition of benzodiazepine receptor binding by some C-benzoyl-1,2,3-triazole derivatives.

Certain new (1-15) or previously described (16-25) 1,2,3-triazole derivatives, characterized by a C-benzoyl substituent, were synthesized and tested for their ability to displace [3H]flunitrazepam from bovine brain membrane. Compounds 11a and 9a, bearing neutral and lipophilic substituents (phenethyl and cyclohexyl, respectively) showed the higher activity. The 5-benzoyl isomer 11b presented a lower activity, equivalent to that of the triazole acetic derivative 23, which is 4-benzyl substituted. Generally, the carboxymethyl radical in the 1-position of the triazole ring decreased the activity, probably because of intramolecular hydrogen bonding with the carbonyl function of the benzoyl substituent. The N-1 unsubstituted triazole derivatives 24 and 25 were ineffective; this result is in disagreement with our previous observations. Probably these molecules interact with the receptor site by a hydrogen bonding acceptor group and by a bulky and lipophilic portion or a hydrogen bonding donor function that is appropriately arranged.

Animals↗
PubMed1993

3 alpha-hydroxy-5 alpha-pregnan-20-one modulation of solubilized GABA/benzodiazepine receptor complex.

The allosteric modulation of the progesterone metabolite 3 alpha- hydroxy-5 alpha-pregnan-20-one (DHP) on [3H]Flunitrazepam and [35S]t-butylbicyclophosphorothionate (TBPS) binding was investigated on a soluble receptor preparation. Better results in the solubilization occurred by the use of the zwitterionic detergent CHAPS with the inclusion of the phospholipid asolectin: this treatment was found suitable to study the steroidal modulation on [3H]Flunitrazepam and [35S]TBPS binding. We found that DHP was able to enhance [3H]Flunitrazepam binding in the presence of Cl- ions, while [35S]TBPS binding was inhibited by DHP. Scatchard analysis of specific [35S]TBPS and [3H]Flunitrazepam binding yielded in a single straight line both in the controls and in the presence of the hormone; DHP increased the apparent affinity of [3H]Flunitrazepam binding without altering the apparent Bmax value. In the case of [35S]TBPS, DHP decreased the apparent Bmax value whereas the Kd value remained nearly the same.

Animals↗
PubMed1993

The peripheral-type benzodiazepine receptor ligands [3H]Ro 5-4864 and [3H]PK 11195 bind to the retina of rabbit, but not of turtle.

The binding of [3H]flunitrazepam, [3H]Ro 5-4864, and [3H]PK 11195 to membrane preparations of the retina was studied in the turtle and rabbit. Only a single population of [3H]flunitrazepam binding sites was detected in the turtle, whereas two populations appeared to be present in the rabbit. No specific binding for [3H]Ro 5-4864 and [3H]PK 11195 could be detected in the turtle. In rabbit, both ligands bound with high affinity, revealing a significant population of binding sites (KD values of 24 +/- 2.3 and 2.2 +/- 0.8 nM, and Bmax values of 440 +/- 35 and 1,482 +/- 110 fmol/mg of protein, respectively). The binding was temperature- and protein-dependent. Displacement studies showed a similar rank order of potency of various unlabeled ligands against both [3H]Ro 5-4864 and [3H]PK 11195 (PK 11195 > Ro 5-4864 > flunitrazepam > flumazenil). These results suggest that peripheral-type benzodiazepine receptors are present in the retina of the rabbit, but not of the turtle.

Animals↗
PubMed1993

Novel adenosine receptor ligands: 1,3-disubstituted[1]benzopyrano[2,3-c]pyrazol-4-ones. Synthesis and structure-activity relationships.

A series of 1,3-disubstituted[1]benzopyrano[2,3-c]pyrazol-4-ones were synthesized and tested in vitro as A1 and A2 adenosine receptor ligands. The binding results and a molecular modelling study indicated that the presence of a proton donor group in the N6-H region of adenosine and the 7-NH region of xanthine, respectively and occupancy of the A2 lipophilic area by a moiety endowed with an electrostatic effect are essential for receptor affinity and A2-selectivity.

Animals↗
PubMed1993

Tricyclic heteroaromatic systems 1,2,4-triazolo[1,5-a]quinoxalines: synthesis and benzodiazepine receptor activity.

The synthesis, the benzodiazepine binding activity and the "in vitro" biological effect of some 1,2,4-triazolo[1,5-a]quinoxalines, 3-aza-analogues of some previously reported pyrazolo[1,5-a]quinoxalines, are described. Molecular modelling is used to define the structural requirements of the benzodiazepine recognition site which influence the affinity and different efficacy of these rigid ligands.

Animals↗
PubMed1993

1,2,3-Triazole[4,5-d]pyridazines--I. Analogues of prostaglandin synthesis inhibitors.

This paper reports the preparation of new triazolepyridazine derivatives bearing in the 1 position an acidic substituent, on the basis of a working hypothesis relating these compounds to 1,2,3-triazole derivatives, effective in vitro inhibitors of the prostaglandin synthesis. The tested compounds were lacking of biological activity.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1993

Synthesis and benzodiazepine receptor affinity of N-(indol-3-ylglyoxylyl)-dipeptide derivatives. Structural requirements for inverse agonist/antagonist receptor interactions.

Several N-(indol-3-ylglyoxylyl)dipeptide derivatives 1-12 were synthesized and tested for their affinity at the benzodiazepine receptor in bovine cortical membranes. They proved to bind with low or no affinity at the receptor site. It was hypothesized that this result was not due to the steric hindrance of the dipeptide side chain, but to the establishment of intramolecular hydrogen bonds involving the indole N-H and/or the glyoxylyl C = O(2). Conformational analysis indicated that coiled conformations, with intramolecular hydrogen bonds, were energetically more favoured than the staggered, completely unfolded ones. Therefore, the low or no affinity of these compounds should be attributed to the unavailability of the N-H and/or C = O(2) groups for the binding, again confirming that both these groups are necessary for interaction with the receptor.

Animals↗
PubMed1993

Xanthine oxidase (XO): relative configuration of complexes formed by the enzyme, 2- or 8-n-alkyl-hypoxanthines and 2-n-alkyl-8-azahypoxanthines. XII.

Several 2- or 8-n-alkyl-hypoxanthines and a 2,8-di-n-pentyl-hypoxanthine were synthesized and tested as substrates or inhibitors of Xanthine Oxidase (XO). 8-Alkyl derivatives showed a substrate behaviour, whereas 2-alkyl substituted compounds were non-substrates and inhibitors. 2,8-di-n-pentyl-hypoxanthine was ineffective as inhibitor. The comparison between their activity allowed us to conclude that the complexes formed by the enzyme and the cited n-alkylhypoxanthines or 2-n-alkyl-8-azahypoxanthines involve their N(3) and N(9) positions in all the cases. The position of the n-alkyl chain determines the disposition of the molecule inside the complex: 2-n-alkyl-hypoxanthines and 2-n-alkyl-8-azahypoxanthines gave complexes with the same orientation of heterocyclic moieties, opposite that given by 8-n-alkyl-hypoxanthines.

Animals↗
PubMed1993

Benzodiazepine receptor affinity and interaction of new indole derivatives.

Recently, several derivatives, in which tryptamine, tyramine, and dopamine moieties are linked to the indole nucleus by an oxalyl bridge, were tested for their affinity and efficacy at the benzodiazepine receptor (BzR). To better define the structure-activity relationships (SAR) several phenylethylamine derivatives were also synthesized and tested for their affinity at the BzR. Compounds bearing a protic group on the aromatic system of the side chain show a pharmacological profile of inverse agonist, while the products lacking this group behave as partial agonist. We now report the affinity data at the BzR of new compounds in which the distance between the phenyl ring and the amide group of the side chain has been changed. The benzylamine derivatives showed a good affinity at the BzR, generally higher than that of the phenylethylamine derivatives. In this series the pharmacological profile showed to be opposite to that of the corresponding phenylethylamine derivatives, since the compounds substituted with protic groups on the phenyl ring behaved as partial agonists. Moreover, a probable interaction with the receptor site is hypothesized.

Animals↗