Biomedical subjects

M Raiteri

Publications and source records attributed to M Raiteri.

At least 91 records · Page 5Linked to original sources

PubMed1996

Human brain N-methyl-D-aspartate receptors regulating noradrenaline release are positively modulated by HIV-1 coat protein gp120.

OBJECTIVE: To investigate the effect of HIV-1 gp120 on the function of glutamate receptors of the N-methyl-D-aspartate (NMDA) type in the human brain. DESIGN: The monitoring of neurotransmitter release from superfused isolated nerve endings is widely recognized as a technique appropriate for the study of neurotransmitter release and to attribute a precise localization to the site(s) of action of drugs able to modulate release. METHODS: Synaptosomes (pinched-off nerve endings) were prepared from fresh human brain tissue samples removed during neurosurgery, labelled with [3H]-noradrenaline and superfused at a rate of 0.5 ml/min with NMDA in the presence of gp41, gp160, gp120 or the V3 loop, with or without NMDA receptor antagonists. Fractions of superfusate were collected and measured for radioactivity. RESULTS: NMDA elicited a glycine-sensitive release of [3H]-noradrenaline from human brain synaptosomes. HIV-1 gp120 potentiated the NMDA (1 mM)-evoked [3H]-noradrenaline release (maximal effect approximately 110% at 1 nM). The release elicited by NMDA plus gp120 was prevented by the classical NMDA receptor antagonists dizocilpine or 7-chlorokynurenic acid, as well as by memantine. The potentiation by gp120 of the NMDA-evoked [3H]-noradrenaline release was mimicked by gp160 but not by gp41. The effect of gp120 was retained by the V3 loop. Finally, gp120 reversed (1 nM) and surmounted (10nM) the antagonism by 10 microM 7-chlorokynurenate of the NMDA-evoked [3H]-noradrenaline release. CONCLUSION: gp 120 binds directly through the V3 loop at noradrenergic axon terminals in human brain neocortex and may alter the function of presynaptic NMDA receptors mediating regulation of noradrenaline release.

Adult↗

PubMed1996

Effect of the new calcium antagonist lercanidipine and its enantiomers on the migration and proliferation of arterial myocytes.

The in vitro effects were investigated of the new dihydropyridine calcium antagonist (CA) lercanidipine and its enantiomers on arterial myocyte (smooth muscle cell; SMC) migration and proliferation as related to L-type calcium channel inhibition. Lercanidipine and its enantiomers inhibited the replication and migration of arterial myocytes in concentration ranging from 10 to 50 microM. The antiproliferative effect of lercanidipine, evaluated as cell number, was dose dependent, with a potency similar to that of lacidipine and nifedipine, and was unrelated to the stereoselectivity of enantiomers to bind L-type calcium channels. The cell doubling time increased with drug concentration < or = 122 versus 38 h for controls. The cell growth inhibition induced by lercanidipine and its enantiomers was reversible. Lercanidipine dose dependently decreased [3H]thymidine incorporation into DNA; the (R)-enantiomer, displaying the lowest CA activity, was the most potent in this respect. The tested compounds were able to inhibit fibrinogen-induced myocyte migration in a dose-dependent manner, with the (R)-enantiomer showing the more pronounced effect. To directly rule out the role of calcium channels in the antiatherosclerotic properties of lercanidipine, we examined the effect of the compounds on serum-stimulated calcium influx in SMC. Fluorimetry of Fluo 3 was used to measure changes in free cytosolic Ca2+ concentration ([Ca2+]i) in SMC after long-term preincubation (24 h) with the tested CA. Lercanidipine and its enantiomers (25 microM) decreased the serum-induced elevation of [Ca2+]i in SMC with the (S)-enantiomer (69% inhibition) 2.4-fold more active than the counterpart and the racemate (29% inhibition). In conclusion, our in vitro results suggest that lercanidipine may directly interfere with events involved in atherogenesis. The studies performed with enantiomers of lercanidipine suggest that the observed effects are not related to the blockade of voltage-dependent Ca2+ channels and confirm at least in vitro a pharmacologic potential of the compound to negatively influence the process of atherogenesis.

Animals↗

PubMed1996

Human brain somatostatin release from isolated cortical nerve endings and its modulation through GABAB receptors.

UNLABELLED: 1. The release of somatostatin-like immunoreactivity (SRIF-LI) in the human brain was studied in synaptosomal preparations from fresh neocortical specimens obtained from patients undergoing neurosurgery to remove deeply sited tumours. 2. The basal outflow of SRIF-LI from superfused synaptosomes was increased about 3 fold during exposure to a depolarizing medium containing 15 mM KCl. The K(+)-evoked overflow of SRIF-LI was almost totally dependent on the presence of Ca2+ in the superfusion medium. 3. The GABAB receptor agonist, (-)-baclofen (0.3 - 100 microM), inhibited the overflow of SRIF-LI in a concentration-dependent manner (EC50 = 1.84 +/- 0.20 microM; maximal effect: about 50%). The novel GABAB receptor ligand, 3-aminopropyl(difluoromethyl)phosphinic acid (CGP 47656) mimicked (-)-baclofen in inhibiting the SRIF-LI overflow (EC50 = 3.06 +/- 0.52 microM; maximal effect: about 50%), whereas the GABAA receptor agonist, muscimol, was ineffective up to 100 microM. 4. The inhibition by 10 microM (-)-baclofen of the K(+)-evoked SRIF-LI overflow was concentration-dependently prevented by two selective GABAB receptor antagonists, 3-amino-propyl (diethoxymethyl)-phosphinic acid (CGP 35348) (IC50 = 24.40 +/- 2.52 microM) and [3-[[(3,4-dichlorophenyl) methyl]amino]propyl] (diethoxymethyl) phosphinic acid (CGP 52432) (IC50 = 0.06 +/- 0.005 microM). 5. The inhibition of SRIF-LI overflow caused by 10 microM CGP 47656 was abolished by 1 microM CGP 52432. 6. When human synaptosomes were labelled with [3H]-GABA and depolarized in superfusion with 15 mM KCl, the inhibition by 10 microM (-)-baclofen of the depolarization-evoked [3H]-GABA overflow was largely prevented by 10 microM CGP 47656 which therefore behaved as an autoreceptor antagonist. 7. IN CONCLUSION: (a) the characteristics of SRIF-LI release from synaptosomal preparations of human neocortex are compatible with a neuronal origin; (b) the nerve terminals releasing the neuropeptide possess inhibitory receptors of the GABAB type; (c) these receptors differ pharmacologically from the GABAB autoreceptors present on human neocortex nerve terminals since the latter have been shown to be CGP 35348-insensitive but can be blocked by CGP 47656.

Adult↗

PubMed1996

In vivo microdialysis study of a specific inhibitor of soluble guanylyl cyclase on the glutamate receptor/nitric oxide/cyclic GMP pathway.

1. Nitric oxide (NO) is known to stimulate soluble guanylyl cyclase, thereby eliciting an elevation of guanosine 3':5'-cyclic monophosphate (cyclic GMP) in target cells. Recently, a selective inhibitor of soluble guanylyl cyclase, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), has been identified and characterized in vitro. We have investigated the in vivo effects of ODQ on the glutamate receptor/NO/ cyclic GMP pathway by monitoring extracellular cyclic GMP during microdialysis of the cerebellum or the hippocampus of freely-moving adult rats. 2. Intracerebellar administration of ODQ (1-100 microM) via the microdialysis probe inhibited, in a concentration-dependent manner, the basal extracellular level of cyclic GMP. The maximal inhibition, measured after a 20 min perfusion with 100 microM ODQ, amounted to 80% and persisted unchanged as long as ODQ was perfused. When ODQ was removed from the perfusion stream after 20 min, the levels of cyclic GMP started to recover, suggesting reversibility of guanylyl cyclase inhibition by ODQ. 3. The cyclic GMP response evoked in the cerebellum by NMDA (200 microM) or by alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA; 100 microM) was largely attenuated by 100 microM ODQ. The pattern of the inhibition curves suggests competition for guanylyl cyclase between ODQ and the NO generated by NMDA or AMPA receptor activation. 4. ODQ (100 microM) prevented the elevation of extracellular cyclic GMP levels provoked by intracerebellar infusion of the NO generator S-nitroso-N-acetylpenicillamine (SNAP; 1 mM). The inhibition of the SNAP effect was rapidly relieved when ODQ was removed from the perfusion fluid. However, ODQ (100 microM) was unable to affect the cyclic GMP response elicited by 5 mM SNAP, in keeping with the proposed idea that ODQ binds to the "NO receptor' in a reversible and competitive manner. 5. Infusion of ODQ (10, 100 or 300 microM) into the hippocampus of freely-moving rats diminished the basal extracellular level of cyclic GMP. The maximal inhibition amounted to 50% and was produced by 100 microM ODQ. 6. The cyclic GMP response observed when 1 mM SNAP was perfused in the hippocampus, similar in percentage terms to that seen in cerebellum, was dramatically reduced during co-infusion of 100 microM ODQ. 7. ODQ appears to act in vivo as a selective, reversible and possibly competitive inhibitor of the soluble guanylyl cyclase targeted by NO. This enzyme may generate most (about 80%) of the cyclic GMP found under basal conditions in the extracellular space of the cerebellum. In the hippocampus, about 50% of the basal cyclic GMP does not seem to originate from the ODQ-sensitive soluble guanylyl cyclase.

Animals↗

PubMed1996

Desensitization of AMPA receptors and AMPA-NMDA receptor interaction: an in vivo cyclic GMP microdialysis study in rat cerebellum.

1. Desensitization is an important characteristic of glutamate receptors of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) type. 2. Stimulation of N-methyl-D-aspartate (NMDA) or AMPA receptors in cerebellum results in increased production of cyclic GMP. We have investigated AMPA receptor desensitization in vivo by monitoring extracellular cyclic GMP during intracerebellar microdialysis in conscious unrestrained adult rats. 3. Local infusion of AMPA (10 to 100 microM) caused dose-related elevations of cyclic GMP levels. The effect of AMPA was prevented by the non-NMDA receptor antagonist, 6,7-dinitroquinoxaline-2,3-dione (DNQX) and by the nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine (L-NOARG). 4. In the absence of AMPA, DNQX lowered the basal levels of cyclic GMP whereas the NMDA receptor channel antagonist dizocilpine (MK-801) was ineffective. 5. Cyclothiazide, a blocker of AMPA receptor desensitization, potentiated the cyclic GMP response to exogenous AMPA. Moreover, cyclothiazide (100-300 microM) produced on its own dose-dependent elevations of extracellular cyclic GMP. The cyclothiazide-induced response was prevented not only by DNQX but also by MK-801. 6. While the cyclic GMP response elicited by AMPA was totally insensitive to MK-801, the response produced by AMPA (10 microM) plus cyclothiazide (30 microM) was strongly attenuated by the NMDA receptor antagonist (30 microM). 7. The results suggest that (a) AMPA receptors linked to the NO-cyclic GMP pathway in the cerebellum can undergo desensitization in vivo during exposure to exogenous AMPA; cyclothiazide inhibits such desensitization; (b) AMPA receptors (but not NMDA receptors) are 'tonically' activated and kept in a partly desensitized state by endogenous glutamate; (c) if cyclothiazide is present, activation of AMPA receptors may permit endogenous activation of NMDA receptors.

Animals↗

PubMed1996

Human brain cholecystokinin: release of cholecystokinin-like immunoreactivity (CCK-LI) from isolated cortical nerve endings and its modulation through GABA(B) receptors.

The release of cholecystokinin-like immunoreactivity (CCK-LI) in human brain was investigated using synaptosomes prepared from neocortical specimens removed during neurosurgery. CCK-LI basal release from superfused synaptosomes was increased 3 to 4-fold during depolarization with 15 mM KCI. The K(+)-evoked overflow of CCK-LI was strictly Ca(++)-dependent. The gamma-aminobutyric acidB (GABA(B)) receptor agonist (-)baclofen (0.3-100 microM) inhibited CCK-LI overflow in a concentration-dependent manner (EC50 = 2.20 microM; maximal effect: 45%). The novel GABA(B) receptor ligand CGP 47656 mimicked (-)baclofen (EC50 = 2.45 microM; maximal effect: 50%), whereas the GABA(A) agonist muscimol was ineffective up to 100 microM. The inhibitory effect of 10 microM (-)baclofen on the CCK-LI overflow was concentration-dependently prevented by two selective GABA(B) receptor antagonists, CGP 35348 (IC50 = 13.91 microM) and CGP 52432 (IC50 = 0.08 microM). The effect of 10 microM CGP 47656 was abolished by 1 microM CGP 52432. In experiments on [3H]GABA release, CGP 47656 behaved as an antagonist at the GABA(B) autoreceptors: added at 10 microM, it prevented the inhibitory effect of 10 microM (-)baclofen on the K+ (15 mM)-evoked release of [3H]GABA from human synaptosomes. We conclude that 1) the release of CCK-LI evoked from human brain tissue appears of neuronal origin; 2) the CCK-releasing terminal possess inhibitory presynaptic GABA(B) receptors; 3) these receptors differ pharmacologically from human neocortex GABA(B) autoreceptors, which are CGP 35348-insensitive (Fassio et al., 1994) but can be blocked by CGP 47656; 4) because cholecystokinin has been implicated in anxiety, the GABA(B) receptors here characterized may represent targets for novel anxiolytic agents.

Benzylamines↗

PubMed1995

Transmitter release associated with long-term synaptic depression in rat corticostriatal slices.

Using a corticostriatal slice preparation, we have recently shown that tetanic stimulation of the corticostriatal pathway produces long-term depression (LTD) of striatal excitatory synaptic transmission. In the present study we have analysed the relationship between LTD and the striatal release of different endogenous transmitters. Samples of perfusate were collected via a small cannula placed just above the surface of the striatal slice close to the recording electrode, and were analysed by HPLC. The high-frequency stimulation (100 Hz, three trains, 3 s duration, 20 s interval) used to induce LTd caused a significant but transient increase in the release of both excitatory (aspartate and glutamate) and inhibitory (glycine and GABA) amino acid transmitters. Tetanic stimulation also produced a significant, but transient increase in the release of endogenous dopamine. We conclude that the tetanic stimulation of the corticostriatal pathway is able to induce a large but transient release of excitatory amino acids and of dopamine, whose participation in the induction of striatal LTD has been demonstrated previously. Moreover, the maintenance of this form of synaptic plasticity does not seem to require a sustained change in transmitter release.

6-Cyano-7-nitroquinoxaline-2,3-dione↗

PubMed1995

Pathogenesis of atherosclerosis and the role of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors.

Atherosclerosis is a complex multifactorial process resulting from an excessive inflammatory/fibroproliferative response to various forms of injurious stimuli to the arterial wall. The potential interactions of cells, cytokines, and growth-regulatory molecules among the different cells in the atherosclerotic lesion present numerous opportunities for modulating lesion formation and progression. Smooth muscle cell (SMC) migration and proliferation, together with lipid deposition, are now recognized as the major phenomena occurring within the arterial wall, and thus these phenomena serve as targets for pharmacologic intervention in the process of atherogenesis. Migration and proliferation of SMC are key events in atherosclerosis--and in restenosis after angioplasty. An understanding of the factors that induce such events is important for the prevention and treatment of these diseases. Mevalonate and other intermediates of cholesterol synthesis (isoprenoids) are essential for cell proliferation; hence drugs affecting this metabolic pathway are potential antiatherosclerotic agents. Recently, this group provided in vitro and in vivo evidence of decreases in SMC proliferation by fluvastatin and simvastatin, but not pravastatin, independent of their cholesterol-lowering properties. The in vitro inhibition of cell migration and proliferation induced by simvastatin and fluvastatin (70-90% decrease) was completely prevented by the addition of mevalonate, and partially prevented (70-80%) by farnesol or geranylgeraniol. This confirms the specific role of isoprenoid metabolites--most probably geranylgerylated protein(s)--in regulating cell migration and proliferation. The inhibitory effect of fluvastatin and simvastatin on cholesterol esterification induced by acetyl low density lipoprotein in macrophages was also prevented by the addition of geranylgeraniol.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Age-related changes in the NMDA receptor/nitric oxide/cGMP pathway in the hippocampus and cerebellum of freely moving rats subjected to transcerebral microdialysis.

The N-methyl-D-aspartate (NMDA) receptor/nitric oxide synthase/guanylate cyclase pathway was studied during aging by monitoring extracellular cGMP in the rat hippocampus and cerebellum during in vivo microdialysis. In the hippocampus the basal cGMP efflux decreased by 50% from 3 to 12 months of age, whereas it remained constant with age in the cerebellum. Locally perfused NMDA (1 mM) evoked remarkable cGMP responses in 3-month-old rats; in the hippocampus the cGMP production was already dramatically reduced at 12 months, whereas in the cerebellum a similar impairment occurred much later (24 months). The nitric oxide donor S-nitroso-N-penicillamine (1 mM) elicited cGMP responses which slightly decreased from 3 to 12-24 months in the hippocampus, while no significant decrement with age could be seen in the cerebellum. Local perfusion of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX, 1 mM) produced large increases in hippocampal cGMP levels. The response decreased at 12 and 24 months, apparently in parallel with the fall in the basal level of cGMP. No significant differences across ages were observed following IBMX infusion in the cerebellum. The decreases in basal outflow and in the NMDA-evoked cGMP response seen in the aged hippocampus were not compensated for by supplying L-arginine. Infusion of D-serine (1 mM) enhanced (150-200%) extracellular cGMP in the cerebellum with no age-related differences. The activity in vitro of hippocampal nitric oxide synthase at 24 months was 33% lower than at 3 months, whereas the cerebellar enzyme did not show any age-related decay.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

PubMed1995

Putative cognition enhancers reverse kynurenic acid antagonism at hippocampal NMDA receptors.

Oxiracetam, aniracetam and D-cycloserine, three putative cognition enhancers, were examined in a functional assay for NMDA receptors. Rat hippocampal slices or synaptosomes were labeled with [3H]noradrenaline and exposed to NMDA or glutamate in superfusion. NMDA (100 microM) elicited a remarkable rise (about 500%) in the release of [3H]noradrenaline from slices. The effect of NMDA was antagonized by the glutamate receptor blocker, kynurenic acid. The antagonism by 100 microM kynurenate was reduced by submicromolar concentrations of oxiracetam and totally reversed by 1 microM of the drug. The concentration-antagonism curve for kynurenic acid was shifted to the right in the presence of 0.2 or 1 microM oxiracetam. Aniracetam and D-cycloserine, as well as glycine and D-serine, behaved similarly to oxiracetam: all compounds, tested at 1 microM, reversed the antagonism by 100 microM kynurenate of the NMDA-evoked [3H]noradrenaline release. In superfused hippocampal synaptosomes, 100 microM NMDA or glutamic acid elicited the release of [3H]noradrenaline; the evoked release was enhanced by glycine, but not by oxiracetam. In this preparation 1 microM glycine or 1 microM oxiracetam prevented the antagonism by kynurenate of the NMDA- or the glutamate-evoked [3H]noradrenaline release. As kynurenic acid is an endogenous glutamate receptor antagonist whose brain levels are known to increase in conditions associated to cognitive deficits, it is proposed that the putative cognition enhancers tested may act in vivo by relieving the antagonism produced by excessive endogenous kynurenate.

Animals↗

PubMed1995

Low nanomolar serotonin inhibits the glutamate receptor/nitric oxide/cyclic GMP pathway in slices from adult rat cerebellum.

The function of serotonin afferents to the cerebellum has been investigated by monitoring the effects of serotoninergic drugs on the production of cyclic GMP elicited in cerebellar slices by activation of ionotropic glutamate receptors. Exposure of adult rat cerebellar slices to N-methyl-D-aspartate (1 nM to 1 microM) or to (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA; 1 nM to 10 microM) elicited concentration-dependent and saturable rises in the levels of cyclic GMP. These responses were blocked by selective antagonists at the N-methyl-D-aspartate or AMPA receptors and by inhibiting nitric oxide synthase, but were insensitive to tetrodotoxin. When tested between 0.1 and 10 nM, serotonin, the serotonin1A receptor agonist (+/-)-8-hydroxy-2-(di-n-propylamino)tetralin and the serotonin2 receptor agonist (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane inhibited, concentration-dependently, the cyclic GMP responses evoked by near-maximal (0.1 microM) concentrations of N-methyl-D-aspartate or AMPA. The EC50 values (concentrations causing half-maximal effect) ranged between 0.7 and 2.1 nM. The actions of serotonin were totally abolished by methiothepin, a mixed-type serotonin receptor antagonist. Thus, the serotonergic cerebellar afferents may exert a potent inhibitory control on the excitatory transmission mediated by N-methyl-D-aspartate and AMPA receptors; the inhibition occurs through both serotonin1A and serotonin2 receptors. As the glutamate receptor-dependent cyclic GMP responses involve production of nitric oxide, a diffusible activator of guanylate cyclase, the above inhibitory serotonin receptors may have multiple localization.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Effects of 26-aminocholesterol, 27-hydroxycholesterol, and 25-hydroxycholesterol on proliferation and cholesterol homeostasis in arterial myocytes.

The major relation existing between cell growth and cholesterol homeostasis prompted us to investigate the effect of 26-aminocholesterol (26-NH2), 27-hydroxycholesterol (27-OH), and 25-hydroxycholesterol (25-OH) on these cellular events. To test this relation, we incubated human and rat arterial myocytes with the sterols for 72 hours. All the tested compounds (0.5 to 7.5 mumol/L) inhibited rat and human myocyte proliferation and cholesterol biosynthesis in a dose-dependent manner. 26-NH2 was more potent than oxysterols in inhibiting human myocyte proliferation but equieffective in rat cells; 27-OH and 25-OH displayed similar activity in both cell lines. Inhibition of nuclear incorporation of thymidine in rat myocytes is consistent with decreased cell count. The antiproliferative effect of the tested sterols was reversible. The high inhibition (80%) of cholesterol biosynthesis necessary to induce a decrease in myocyte proliferation suggests a causal relation between the cholesterol synthetic pathway and these cellular processes. In addition, all the tested sterols were able to inhibit hydroxymethyl glutaryl-coenzyme A reductase activity in intact myocytes but not in cell-free extracts. The finding that 26-NH2 but not 27-OH or 25-OH does not suppress LDL receptor activity in either human or rat myocytes supports the achievement of selectivity over the coordinately regulated LDL receptor gene. The ability of 26-NH2 to interfere with myocyte proliferation and cholesterol synthesis without affecting the LDL receptor pathway confers at least in vitro a pharmacological interest on the compound in the process of atherogenesis.

Animals↗

PubMed1995

In vitro and in vivo effects of d-fenfluramine: no apparent relation between 5-hydroxytryptamine release and hypophagia.

The anorexigenic drug d-fenfluramine (d-F) increased the in vitro release of [3H]5-hydroxytryptamine ([3H]-5-HT) from rat hypothalamic synaptosomes. The release induced by 5 microM d-F was Ca(++)-independent, insensitive to 5-HT autoreceptor activation and prevented by the 5-HT uptake inhibitor fluoxetine (0.1 microM). The release evoked by 0.5 microM d-F also was blocked by fluoxetine, but it was Ca(++)-dependent and sensitive to autoreceptor activation. Thus, relatively high concentrations of d-F release 5-HT through an outward carrier mediated transport; at 0.5 microM the evoked release seems instead exocytotic, although it probably requires previous uptake of d-F by the 5-HT transporter. During in vivo intrahypothalamus microdialysis, in free-moving rats, local infusion (0.5 or 5 microM) or i.p. administration (0.8 or 2.5 mg/kg) of d-F produced increases of extracellular 5-HT. These effects were prevented completely by local (0.1 microM) or i.p. (1 mg/kg) administration of fluoxetine. Although both 0.8 and 2.5 mg/kg of d-F consistently increased hypothalamic extracellular 5-HT, only the higher dose induced hypophagia. This hypophagia was, however, not significantly modified by fluoxetine, although it was blocked by the 5-HT receptor antagonist metergoline (2 mg/kg i.p.). The results show that d-F is a potent 5-HT releaser also in the hypothalamus, one major site of action of the anorexigenic drug. Depending on the concentration, the release elicited by d-F may occur by a dual mechanism requiring integrity of the 5-HT transporter.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Safe utilization and long-term follow-up of 368 marginal kidneys.

Three-hundred sixty-eight grafts of 1701 KTs performed during a 25-year period showed major anatomical anomalies: 358 kidneys presented an abnormal vascular supply, 8 organs had a double ureters, 2 were indivisible horseshoe kidneys. The outcome of these MKs is virtually identical (84%) to those obtained with transplant of normal grafts (85%). The advantages of ex vivo arterioplasty have been advocated.

Anastomosis, Surgical↗

PubMed1995

[The pharmacology of the statins: the evidence of a direct antiatherosclerotic action].

With the increasing knowledge on the pathogenesis of atherosclerosis, it appears that the prevention of cardiovascular disease in the future will involve, besides risk factor correction, direct pharmacological control of processes occurring in the arterial wall. Among them, a pivotal role is played by smooth muscle cell migration and proliferation that, together with lipid deposition, are prominent features of atherogenesis and restenosis after angioplasty. Mevalonate and other intermediates (isoprenoids) of cholesterol synthesis are essential for cell growth, hence drugs affecting this metabolic pathway are potential antiatherosclerotic agents. Recently we provided evidence that fluvastatin, simvastatin, lovastatin, but not pravastatin, dose-dependently decrease smooth muscle cell migration and proliferation, independently of their hypocholesterolemic properties. The in vitro inhibition of cell migration and proliferation induced by simvastatin and fluvastatin (70-90% decrease) was completely prevented by the addition of mevalonate and partially (80%) by farnesol and geranylgeraniol, confirming the specific role of isoprenoid metabolites--probably through prenylated proteins--in regulating these cellular events. The present results provide evidence that HMG-CoA reductase inhibitors interfere directly with processes involved in atherogenesis--beyond their effects on plasma lipids--partially through local inhibition of isoprenoid biosynthesis.

Animals↗

PubMed1994

HIV-1 envelope protein gp120 potentiates NMDA-evoked noradrenaline release by a direct action at rat hippocampal and cortical noradrenergic nerve endings.

Exposure of rat or human neocortical or hippocampal tissue to glutamate receptor agonists elicits as Ca(2+)-dependent, exocytotic-like release of previously accumulated [3H]noradrenaline through activation of both N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors colocalized on the noradrenergic axon terminals. Here we show that the NMDA (100 microM)-evoked release of [3H]noradrenaline from superfused thin layers of isolated rat hippocampal or cortical nerve endings was potentiated when the human immunodeficiency virus type 1 coat protein gp120 was added to the superfusion medium concomitantly with NMDA. The effect of gp120 (10 pM to 3 nM) on the 100 microM NMDA-evoked release of [3H]noradrenaline was concentration-dependent; the maximal effect (approximately 140% potentiation) was reached at 100 pM of gp120. The protein was inactive on its own. The [3H]noradrenaline release evoked by NMDA (100 microM)+gp120 (100 pM) was prevented by classical NMDA receptor antagonists, as well as by 10 microM memantine. Neither the release evoked by NMDA nor that elicited by NMDA+gp120 was sensitive to the nitric oxide synthase inhibitor NG-nitro-L-arginine, suggesting no involvement of nitric oxide. The [3H]noradrenaline release elicited by 100 microM AMPA was unaffected by gp120. The protein potentiated the release evoked by 100 microM glutamate; the effect of 100 pM gp120 was quantitatively identical to that of 1 microM glycine, with no apparent additivity between gp120 and glycine. The antagonism by 1 microM 7-chloro-kynurenic acid of the NMDA-induced [3H]noradrenaline release was reversed by glycine or gp120.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Characterization of the GABA autoreceptor in human neocortex as a pharmacological subtype of the GABAB receptor.

Release-regulating gamma-aminobutyric acidB (GABAB) autoreceptors were studied in synaptosomes from fresh specimens of human cerebral cortex. The K+ (12 mM)-evoked overflow of [3H]GABA was inhibited by the GABAB receptor agonists (-)-baclofen (EC50 = 1.48 microM) and 3-aminopropylphosphinic acid (3-APPA; EC50 = 0.034 microM). The effect of 10 microM (-)-baclofen was differentially reduced by the three GABAB receptor antagonists CGP 52432 ([3-[[(3,4-dichlorophenyl)methyl)amino]propyl]-(diethoxymethyl)- phosphinic acid), phaclofen and CGP 35348 (3-aminopropyl-(diethoxymethyl)- phosphinic acid). CGP 52432 was by far the most potent antagonist (IC50 = 0.09 microM). Phaclofen was about 700-fold less potent than CGP 52432 (IC50 = 70.0 microM) while CGP 35348 was ineffective up to 100 microM. The present results suggest that human and rat GABAB neocortical autoreceptors have similar pharmacological characteristics.

Adolescent↗

PubMed1994

Heterocarrier-mediated reciprocal modulation of glutamate and glycine release in rat cerebral cortex and spinal cord synaptosomes.

The effects of glutamic acid (Glu) and glycine (Gly) on each others release were studied using rat brain cortex and spinal cord synaptosomes. Previously taken up [3H]Gly and [3H]D-aspartic acid ([3H]D-Asp) was employed as markers for Gly and Glu/Asp release, respectively. Glu enhanced the release of [3H]Gly (EC50 = 8.4 microM) from cortical synaptosomes. The effect of Glu was not mimicked by the glutamate receptor agonists N-methyl-D-aspartic acid (NMDA), kainic or quisqualic acid. The Glu effect was abolished by the Glu/Asp uptake inhibitor D-threo-hydroxy-aspartic acid and it was Na+ sensitive. D-Asp also increased [3H]Gly release (EC50 = 9.9 microM) and the effect was blocked by the Glu/Asp uptake inhibitor. In contrast to its effect in the cortex, Glu failed to increase the release of [3H]Gly from spinal cord synaptosomes. Gly enhanced the outflow of [3H]D-Asp from rat cerebral cortex and spinal cord synaptosomes (EC50 = 75.0 and 99.5 microM, respectively). Gly was much more potent a releaser of [3H]D-Asp in the spinal cord than in the cortex. The Gly effects were insensitive to strychnine or to 7-Cl-kynurenic acid, antagonists at the two known Gly receptors, but they were strongly Na+ dependent. Our results are compatible with the idea that high-affinity uptake systems specific for Glu/Asp or Gly are colocalized on the same nerve terminal in rat spinal cord and cerebral cortex.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗