Biomedical subjects

G Giannaccini

Publications and source records attributed to G Giannaccini.

At least 37 records · Page 2Linked to original sources

PubMed2000

Increased density of the platelet serotonin transporter in autism.

BACKGROUND: Various data have shown the involvement of serotonin (5-HT) in autism. The presence of the 5-HT transporter in platelets, similar to the same structure located in presynaptic serotonergic neurons, has produced a series of studies aimed at assessing its functionality in this disorder, but the ensuing findings are quite controversial. For this reason, we investigated the 5-HT transporter by means of the specific binding of [3H]-Paroxetine ([3H]-Par), which is currently considered the first-choice ligand for labeling it, in platelets of 20 autistic children and adolescents, as compared with healthy control subjects. METHODS: Twenty children and adolescents of both sexes suffering from autism according to DSM IV criteria were included in the study and compared with a similar group of healthy control subjects. Platelet membranes and the binding of [3H]-Par were carried out according to standardized protocols. RESULTS: The results showed a significantly higher density of [3H]-Par binding sites in autistic children than in healthy control subjects. CONCLUSIONS: These findings support the presence of a serotonergic dysfunction in autism and would suggest that the 5-HT transporter may have a specific role in this disorder, also in the light of its recently proposed role in brain development.

Adolescent↗

PubMed2000

Simultaneous plasma level analysis of clomipramine, N-desmethylclomipramine, and fluvoxamine by reversed-phase liquid chromatography.

A simple reversed-phase liquid chromatographic method enabling the simultaneous analysis in plasma of the tricyclic antidepressant clomipramine, its demethylated metabolite, and the selective serotonin reuptake inhibitor fluvoxamine, was developed. The drugs and dibenzepine, the internal standard, were extracted from 1 mL plasma through an automated solid-phase procedure, eluted in a total chromatographic time of approximately 14 min and detected by means of an ultraviolet spectrophotometer preset at 254 nm. An assay sensitivity of 10 microg/L was observed for all analytes. Recoveries for these drugs and their metabolites ranged between 65% and 98% and their coefficient of variation (within-day and day-to-day) between 1.9% and 2.9%. In spiked plasma, within-day and day-to-day imprecision data were less than 5%. The simultaneous determination of clomipramine, N-desmethylclomipramine, and fluvoxamine with adequate sensitivity and accuracy may be useful for the monitoring of drug treatment in depression and obsessive-compulsive disorder, where combinations of such drugs are employed.

Adult↗

PubMed2000

Increased inhibitory activity of protein kinase C on the serotonin transporter in OCD.

Different observations show a reduced functionality of the serotonin (5-HT) transporter in obsessive-compulsive disorder (OCD) that might be due to a disturbance of its regulation at intracellular level. Protein kinase C (PKC) has been reported to provoke a decrease in the number of the 5-HT transporter proteins. Therefore, we investigated whether OCD patients differed from control subjects in the effect of PKC upon the 5-HT transporter, after stimulation of this enzyme with 4beta-12-tetradecanoylphorbol 13-acetate (beta-TPA). Fifteen patients affected by OCD, according to DSM-IV criteria, were compared with a similar group of healthy subjects. The determination of 5-HT uptake was carried out according to the method of Arora and Meltzer with slight modifications. At baseline, OCD patients showed a significant decrease in the maximal velocity (V(max)) of 5-HT uptake, as compared with control subjects, with no change in the Michaelis-Menten constant (K(m)). The activation of PKC with beta-TPA provoked a significant decrease in V(max) values in both groups, but the effect was significantly more robust in OCD patients who, in turn, also showed also an increase in K(m) values. These findings could indicate the presence of hyperactivity of PKC in OCD that could be the result of increased activity of the phosphatidylinositol pathway. In addition, this suggests new potential therapeutic targets in OCD.

Adolescent↗

PubMed1999

Platelet [3H]paroxetine binding in patients with OCD-related disorders.

The recently introduced notion of clinical conditions being related one to another, the spectrum concept, permits the testing of the involvement of serotonergic systems in a broad range of disorders tentatively linked to obsessive-compulsive disorder (OCD) for which no pathophysiological hypotheses yet exist. We therefore compared the binding of [3H]paroxetine ([3H]Par), a ligand that specifically labels the serotonin (5-HT) transporter, in platelets of drug-free outpatients suffering from various OCD-related disorders with binding in platelets of OCD patients and healthy subjects. Diagnoses were made according to DSM-IV criteria. The most frequent diagnosis was that of body dysmorphic disorder, followed by impulse control disorder, kleptomania, Tourette's syndrome and trichotillomania. Platelet membranes and [3H]Par binding were studied according to standardized protocols. The results, showing a similarly decreased density of [3H]Par binding sites in both patient groups as compared with healthy subjects, suggest the presence of a shared abnormality at the level of the presynaptic 5-HT transporter, probably linked to a common dimension yet to be identified.

Adolescent↗

PubMed1999

Regulation of the platelet serotonin transporter by protein kinase C in the young and elderly.

BACKGROUND: Some data show that different factors may influence the serotonin (5-HT) uptake rate. Our study aimed at evaluating the possible role of a protein kinase C (PKC) activator, i.e., 4-beta-12-tetradecanoylphorbol-13-acetate (beta-TPA) on the platelet 5-HT uptake of young and elderly subjects, through the measurement of the 5-HT uptake itself and 3H-paroxetine ([3H]PAR) binding sites, which correspond to the transporter protein. METHODS: Human platelets and 5-HT uptake were evaluated according to the method of Arora and Meltzer, while [3H]PAR binding was performed following the Marazziti et al method. RESULTS: The results showed that beta-TPA reduced significantly the maximal velocity (Vmax) of 5-HT uptake, with no change in the Michaelis constant or in [3H]PAR binding parameters, in platelets of both young and elderly subjects. Although this last group of subjects had a significantly lower Vmax than the other, the degree of inhibition was almost the same (75%) in both. CONCLUSIONS: These findings indicate that PKC decreases the 5-HT uptake rate by modifying the phosphorylation state of the transporter and with no change in the number of [3H]PAR binding sites. The responsiveness of this pathway is identical in both young and elderly subjects.

Adult↗

PubMed1999

Effects of postmortem delay on serotonin and (+)8-OH-DPAT-mediated inhibition of adenylyl cyclase activity in rat and human brain tissues.

The reproducibility of serotonin (5-HT) and (+)8-OH-DPAT-mediated inhibition of adenylyl cyclase activity was assessed in membranes, stimulated by forskolin, of rat frontal cortex postmortem as well as of human fronto-cortical, hippocampal and dorsal raphe tissues obtained from autopsy brains. The results revealed that differences between basal and forskolin-stimulated enzyme activities were still significant after 48 h postmortem in rat cortex and in all human brain regions up to 46 h after death. However, a decrease of about 17 and 26% in forskolin-stimulated adenylyl cyclase activity was observed at 24 and 48 h, respectively, in rat cortex. 5-HT and the 5-HT1A receptor agonist, (+)8-hydroxy-2(di-N-propylamino)tetraline (8-OH-DPAT), were able to inhibit forskolin-stimulated adenylyl cyclase activity in a dose-dependent manner for 48 h after death in rat and human brain. In rat cortex, both 5-HT and (+)8-OH-DPAT potencies (EC50, nM) and efficacies (percent of maximum inhibition capacity, %) varied significantly with postmortem delay. Conversely, in human tissues, postmortem delay and subject age did not modify agonist potencies and efficacies. Furthermore, a regionality of 5-HT potency and efficacy was revealed in the human brain. 5-HT was equally potent in cortex and raphe nuclei, while being more potent but less effective in hippocampus. (+)8-OH-DPAT was more active in hippocampus and raphe nuclei than in cortex. (+)8-OH-DPAT behaved as an agonist in all areas, as its efficacy was similar or greater than those obtained with 5-HT. The (+)8-OH-DPAT dose-response curve was completely reversed by 5-HT1A receptor antagonists in rat cortex and all human brain areas. In conclusion, we suggest here that differences between rat and human brain might exist at the level of postmortem degradation of 5-HT-sensitive adenylyl cyclase activity. In human brain, 5-HT1A receptor-mediated inhibition of adenylyl cyclase seems to be reproducible, suggesting that reliable experiments can be carried out on postmortem specimens from patients with neuropsychiatric disorders.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed1999

Decreased platelet 3H-paroxetine binding in untreated panic disorder patients.

Different findings support the involvement of the serotonin (5-HT) system in panic disorder. The presence of the 5-HT transporter in blood platelets similar to that in presynaptic serotonergic neurons, permits the investigation of this structure in periphery. We therefore evaluated the binding of 3H-paroxetine, a selective 5-HT reuptake inhibitor which is considered the ligand of choice for labelling the 5-HT transporter, in platelets of 20 drug-free patients with panic disorder. The same measurement was repeated after one year's treatment with different drugs. The results showed patients to have a lower number of 3H-paroxetine sites than a group of age- and sex-matched controls, thus suggesting the involvement of the 5-HT transporter in panic disorder. This abnormality reverted after one year of treatment with specific drugs that provoked the symptom remission in all cases, which would suggest a link with the clinical improvement.

Adolescent↗

PubMed1999

Distribution and characterization of [3H]mesulergine binding in human brain postmortem.

Much interest is currently being directed towards serotonin (5-HT) receptors of type 2C (5-HT2C) because of their possible involvement in the control of different activities, such as the composition of the cerebrospinal fluid, locomotion, feeding, neuronal excitability and anxiety. The limited information regarding their distribution in the human brain prompted us to investigate, and to characterize the binding of [3H]mesulergine, a HT2C antagonist, in autopsy samples from 24 subjects. The results showed that the [3H]mesulergine binding represented 95% of the total binding and equilibrium saturation binding experiments resulted in a single straight line, consistent with the presence of one site only. The area with the highest density of [3H]mesulergine binding was the choroid plexus, followed at a significantly lower level by the hippocampus, substantia nigra, basal ganglia, amygdala, hypothalamus and prefrontal cortex. The pharmacological profile of the [3H]mesulergine binding was consistent with that of 5-HT2C receptors, since the most effective displacers were ritanserin, mesulergine and mianserine, followed by clozapine, ketanserine and m-CPP, while other compounds had a negligible or no effect. These findings, showing a wide distribution of [3H]mesulergine binding sites in the human brain, could provide anatomical bases for the different functions attributable to 5-HT2C receptors in humans.

Adult↗

PubMed1999

Synthesis of new pyridazinone derivatives and their affinity towards alpha1-alpha2-adrenoceptors.

A series of 3(2H)-pyridazinone derivatives was evaluated for their affinity in vitro towards alpha1-alpha2-adrenoceptors by radioligand receptor binding assays. All target compounds showed good affinities for the alpha1-adrenoceptor (with Ki values in the subnanomolar range), and a gradual increase in affinity was observed by increasing the polymethylene chain length of this series up to a maximum of six and seven carbon atoms, when the fragment 4-[2-(2-methoxyphenoxy)-ethyl]-1-piperazinyl is linked in 5 position of the 3(2H)-pyridazinone ring, while a slight decrease was found for the higher homologues. Increasing the chain length when the 4-[2-(2-methoxyphenoxy)-ethyl]-1-piperazinyl group is linked in 6 position of the 3(2H)-pyridazinone ring, had a different effect: there is the highest affinity when the polymethylene chain is of four carbon atoms. The alkylic chain, a spacer between the two major constituents of the molecule, can influence the affinity and the selectivity.

Animals↗

PubMed1998

N-n-Propyl-substituted 3-(dimethylphenyl)piperidines display novel discriminative properties between dopamine receptor subtypes: synthesis and receptor binding studies.

3-Phenylpiperidines (PPEs) have been thoroughly investigated in view of their interesting dopaminergic activity, and the N-n-propyl substitution has been suggested as the most effective among several PPEs differently substituted on the phenyl ring. In previous studies, we found that the dimethyl substitution on the phenyl ring of N-unsubstituted PPEs provided compounds active toward alpha2-adrenergic receptors (alpha2-ARs), which proved to possess interesting selectivity properties. The high degree of homology between the binding domains of alpha2-ARs and D4-dopaminergic receptors (D4-DARs) prompted us to verify whether this kind of substitution on the aromatic ring might prove to be active against retinal DARs of the D4 subtype. On the basis of these premises, we synthesized the dimethylphenyl-substituted PPEs 4a-f, in which an n-propyl chain is present on the aminic nitrogen. Radioligand binding assays on bovine retina and striatum membranes for D1-like and D2-like DARs indicated that PPEs 4a, 4b, and 4f possess a high affinity and selectivity for the D4-DAR subtype of bovine retina.

Animals↗

PubMed1998

Characterization of sulfonylurea receptors in isolated human pancreatic islets.

Current information on pancreatic islet sulfonylurea receptors has been obtained with laboratory animal pancreatic beta cells or stable beta-cell lines. In the present study, we evaluated the properties of sulfonylurea receptors of human islets of Langherans, prepared by collagenase digestion and density-gradient purification. The binding characteristics of labeled glibenclamide to pancreatic islet membrane preparations were analyzed, displacement studies with several oral hypoglycemic agents were performed, and these latter compounds were tested as for their insulinotropic action on intact human islets. [3H]glibenclamide saturable binding was shown to be linear at < or =0.25 mg/ml protein; it was both temperature and time dependent. Scatchard analysis of the equilibrium binding data at 25 degrees C indicated the presence of a single class of saturable, high-affinity binding sites with a Kd value of 1.0+/-0.07 nM and a Bmax value of 657+/-48 fmol/mg of proteins. The displacement experiments showed the following rank order of potency of the oral hypoglycemic agents we tested: glibenclamide = glimepiride > tolbutamide > chlorpropamide >> metformin. This binding potency order was parallel with the insulinotropic potency of the evaluated compounds.

ATP-Binding Cassette Transporters↗

PubMed1998

N'-Phenylindol-3-ylglyoxylohydrazide derivatives: synthesis, structure-activity relationships, molecular modeling studies, and pharmacological action on brain benzodiazepine receptors.

A series of N'-phenylindol-3-ylglyoxylohydrazides, isosters of the N-benzylindol-3-ylglyoxylamide derivatives previously described by us, were synthesized and tested for their ability to displace [3H]Ro 15-1788 from bovine brain membranes. These compounds were designed with the aim of obtaining products which could exert an in vivo activity, thanks to a higher hydrosolubility and consequently a better bioavailability. Affinity was restricted to the derivatives unsubstituted in the 5 position of the indole nucleus (1, 6, 9, 12, 15, 18, 23, and 26), with Ki values ranging from 510 to 11 nM. The most active compounds (6, 9, 23, and 29) proved to be effective in antagonizing pentylenetetrazole-induced seizures. Molecular modeling studies were performed to rationalize the lack of affinity of hydrazides with a chloro or a nitro group in the 5 position of the indole nucleus. It was hypothesized that the conformational preference of the hydrazide side chain, characterized by a gauche disposition of lone pairs and substituents about the N-N bond, prevents all hydrazides from binding to the receptor similarly to other classes of indole analogues previously investigated. The potency of 5-H hydrazides was attributed to a binding mode which is not feasible for 5-Cl and 5-NO2 counterparts. This theoretical model of ligand-receptor interaction permitted a more stringent interpretation of structure-affinity relationships of hydrazides and of recently described benzylamide derivatives (Da Settimo et al. J. Med. Chem. 1996, 39, 5083-5091).

Animals↗

PubMed1998

Novel 3-aralkyl-7-(amino-substituted)-1,2,3-triazolo[4,5-d]pyrimidines with high affinity toward A1 adenosine receptors.

Three series of several 1,2,3-triazolo[4,5-d]pyrimidine derivatives bearing various amino substituents at the 7 position and one of three lipophilic substituents at the 3 position (benzyl, phenethyl, or 2-chlorobenzyl) were prepared starting from the corresponding 7-chloro compounds, by nucleophilic substitution by the appropriate amine. Radioligand binding assays at bovine brain adenosine A1 and A2A receptors showed that some compounds possessed a high affinity and selectivity for the A1 receptor subtype. In particular the biological results suggested the compounds bearing cycloalkylamino (cyclopentyl- and cyclohexylamino) or aralkylamino (alpha-methylbenzyl- and 1-methyl-2-phenylethylamino or amphetamino) substituents at the 7 position were the most active derivatives. The best lipophilic substituent at the 3 position was the 2-chlorobenzyl (A1 affinity Ki < 50 nM) followed by the benzyl and then the phenethyl groups. This pattern of structure-activity relationship (SAR) was similar to that previously reported for analogous 1,2,3-triazolopyridazino derivatives (Biagi et al., 1994, 1995, 1996) except for the compounds bearing substituted aromatic amines which presented a generalized and strong decrease of the A1 receptor affinity. These facts allowed us to attribute to these molecules a binding mode within the A1 adenosine receptor analogous to that of the corresponding triazolopyridazines.

Adenosine↗

PubMed1998

1,2,3-Triazolo[1,5-a][1,4]- and 1,2,3-triazolo[1,5-a]-[1,5]benzodiazepine derivatives: synthesis and benzodiazepine receptor binding.

This paper reports the synthesis of new 1,2,3-triazolo[1,4]benzodiazepine and 1,2,3-triazolo[1,5]benzodiazepine derivatives and their evaluation toward benzodiazepine receptors. Receptor affinity gradually and remarkably increases by moving the nitrogen atom of the central ring from position 3 through 4 to position 5, to give the most effective compound 6a (Ki = 150 nM). N-methylation of the diazepine ring (7a) lowers receptorial binding. Introduction of a chlorine atom on the benzene ring doubles the Ki value (6b) which remains unaltered by the N-methylation (7b).

Animals↗

PubMed1998

Effect of aging and sex on the [3H]-paroxetine binding to human platelets.

Since there exist conflicting results with regard to the possible effect of aging on platelet [3H]-imipramine binding, taken as a peripheral marker of the serotonin (5-HT) transporter, we reinvestigated this matter by comparing the binding of the more selective ligand [3H]-paroxetine in 20 aged and 23 young subjects. The results showed that neither the maximum binding capacity nor the dissociation constant (Kd) were significantly different in the two groups. When the subjects were compared according to sex, the young females revealed a statistically significant lower Kd than the males, while the contrary was true for the aged females. The Kd was significantly and negatively correlated to age in males. In addition, a significant age x gender interaction was also observed. Therefore, the sex of a subject would seem to provoke significant age-related changes in the Kd of [3H]-paroxetine binding to platelet membranes. This might indicate modifications in the 5-HT transporter that could form the basis of a sex-related difference in vulnerability to disorders, such as depression, where a dysfunction at this level is hypothesized.

Adult↗

PubMed1998

Presence and characterization of the serotonin transporter in human resting lymphocytes.

Although evidence exists of the presence of a serotonin (5-HT) reuptake system in lymphocytes, no information is available on the pharmacological characterization of this structure. Our study aimed to investigate this matter, therefore, by means of the binding of [3H]-paroxetine ([3H]PAR), a selective 5-HT reuptake inhibitor (SSRI), which is considered the ligand of choice for binding studies. Lymphocytes were obtained from a pool of 20 healthy subjects who volunteered for the study. The results showed the presence of a specific and saturable [3H]PAR binding to lymphocyte membranes, with a Hill number close to unity indicative of the presence of one site only. The most potent drugs inhibiting [3H]PAR binding were SSRIs (paroxetine, fluoxetine, citalopram) followed by clomipramine, imipramine, and 5-HT, whereas haloperidol, mazindol, and nomifensine had a negligible effect. These findings suggest that [3H]-PAR in human resting lymphocytes specifically labels the 5-HT transporter.

Adolescent↗

PubMed1997

Apparent absence of aging and gender effects on serotonin 1A receptors in human neocortex and hippocampus.

The effects of gender, aging and gender x age on the binding of the 5-HT1A receptor high-affinity agonist [3H]8-hydroxy-2(di-N-propylamino)tetralin ([3H]8-OH-DPAT), were evaluated and compared in tissues of human prefrontal, temporal, parietal, occipital cortex and hippocampus obtained from 21 autopsy subjects. The results revealed no variation with age or gender in either the [3H]8-OH-DPAT maximum binding capacity (Bmax) or dissociation constant (Kd) values. On the other hand, when separate correlations to subject ages were performed for men and women, aging effects on [3H]8-OH-DPAT Bmax and Kd were detected: in men, a significant age-dependent decrease in Kd values was observed in the occipital cortex; in women, the Bmax significantly decreased with aging in the parietal cortex and hippocampus, while increasing in occipito-cortical membranes. Overall, the present study reveals that, although neither gender nor aging 'per se' seem to modify the 5-HT1A receptor binding, gender may reveal region-specific aging effects, i.e. on receptor affinity in men and receptor density in women. Such findings should stimulate further investigation on the hypothesized existence of gender x age-related cross-connections between serotonergic system and hypothalamus-pituitary-gonadal circuits.

Adult↗

PubMed1997

Binding of the benzodiazepine ligand [3H]-Ro 15-1788 to brain membrane of the saltwater fish Mullus surmuletus.

The distribution and the pharmacological properties of the binding of the benzodiazepine receptor antagonist [3H]-Ro 15-1788 (8-fluoro-3-carboethoxy-5,6-dihydro-5-methyl-6-oxo-4H imidazol [1,5-a] 1,4 benzodiazepine) were compared in some brain membranes of the saltwater teleost fish, Mullus surmuletus: only a single population of [3H]-Ro 15-1788 binding sites was detected. The binding was saturable and reversible with a high affinity, revealing a significant population of binding sites (Kd value of 2.1 +/- 0.2 nM and Bmax value of 1400-900 fmol mg-1 of protein, depending on fish length). The highest concentration of benzodiazepine recognition sites labelled with [3H]-Ro 15-1788 was present in the optic lobe and the olfactory bulb and the lowest concentration was found in the medulla oblongata, cerebellum and spinal cord. In order to explore behavioural selectivity as a consequence of multiple receptor subtypes, six benzodiazepine receptor ligands, flunitrazepam (5-(2-fluoro-phenyl)-1,3-dihydro-1-methyl-7-nitro-2H-1, 4-benzodiazepin-2-one), alpidem, (N,N-dipropyl-6-chloro-2-(4-chlorophenyl)imidazo [1,2-a] pyridine-3- acetamide) zolpidem {N,N,6, trimethyl-2-(4-methyl-phenyl) imidazo [1,2-a] pyridine-3-acetamide hemitartrate}, methyl beta carboline-3-carboxylate (beta CCM), Ro 15-1788 and Ro 5-4864 (4'-chlorodiazepam), were tested in vitro by binding of [3H]-Ro 15-1788 to membrane preparations from various brain areas of Mullus surmuletus, Displacement studies showed a similar rank order of efficacy of various unlabelled ligands. In all regions of the brain and in the spinal cord. GABA potentiate [3H]-flunitrazepam binding in a similar order, suggesting that the BDZ recognition sites are part of the GABAA receptor structure. These results suggest that central-type benzodiazepine receptors are present in one class of benzodiazepine binding sites in the saltwater teleost fish brain of Mullus surmuletus (type I-like). Here we report initial evidence of homogeneity of subtypes of central benzodiazepine receptors in the spinal cord of the saltwater teleost fish. Mullus surmuletus.

Animals↗