Lorenzo Cima

Effect of acute and chronic tramadol on [3H]-5-HT uptake in rat cortical synaptosomes

1 Tramadol hydrochloride is a centrally acting opioid analgesic, the efficacy and potency of which is only five to ten times lower than that of morphine. Opioid, as well as non‐opioid mechanisms, may participate in the analgesic activity of tramadol. 2 [3H]‐5‐hydroxytryptamine (5‐HT) uptake in rat isolated cortical synaptosomes was studied in the presence of tramadol, desipramine, fluoxetine, methadone and morphine. Methadone and tramadol inhibited synaptosomal [3H]‐5‐HT uptake with apparent Kis of 0.27±0.04 and 0.76±0.04 μM, respectively. Morphine essentially failed to inhibit [3H]‐5‐HT uptake (Ki 0.50±0.30 M). 3 Methadone, morphine and tramadol were active in the hot plate test with ED50s of 3.5, 4.3 and 31 mg kg−1, respectively. At the highest tested dose (80 mg kg−1) tramadol produced only 77±5.3% of the maximal possible effect. 4 When [3H]‐5‐HT uptake was examined in synaptosomes prepared from rats 30 min after a single dose of morphine, methadone or tramadol, only tramadol (31 mg kg−1, s.c., equal to the ED50 in the hot plate test) and methadone (35 mg kg−1, s.c., equal to the ED90 in the hot plate test) decreased uptake. 5 Animals were chronically treated for 15 days with increasing doses of tramadol or methadone (5 to 40 mg kg−1 and 15 to 120 mg kg−1, s.c., respectively). Twenty‐four hours after the last drug injection, a challenge dose of methadone (35 mg kg−1, s.c.) or tramadol (31 mg kg−1, s.c.) was administered. [3H]‐5‐HT uptake was not affected in synaptosomes prepared from rats chronically‐treated with methadone, whereas chronic tramadol was still able to reduce this parameter by 42%. 6 Rats chronically‐treated with methadone showed a significant increase in [3H]‐5‐HT uptake (190%) 72 h after drug withdrawal. In contrast, [3H]‐5‐HT uptake in rats chronically‐treated with tramadol (110%) did not differ significantly from control animals. 7 These results further support the hypothesis that [3H]‐5‐HT uptake inhibition may contribute to the antinociceptive effects of tramadol. The lack of tolerance development of [3H]‐5‐HT uptake, together with the absence of behavioural alterations after chronic tramadol treatment, suggest that tramadol has an advantage over classical opioids in the treatment of pain disorders.

Bioaccumulation of Hg in the mushroom Pleurotus ostreatus

The possibility of utilizing industrial, urban, and other wastes for the growth of a product which is directly edible by humans is fascinating. However, it is possible that many wastes containing toxic substances, for example, heavy metals, could reach the food chain and produce adverse effects on human health. To this end, we studied the possibility of bioaccumulation of Hg by a mushroom, Pleurotus ostreatus, grown on an artificial compost containing this element. Concentrations of 0.05, 0.1, and 0.2 mg/kg of Hg as Hg(NO3)2.H2O were added to three groups of the same compost, successively inoculated with the mycelia of the mushroom. Higher concentrations strongly reduced the growth of the mycelia and therefore were not utilized. The concentrations of Hg in the substrate and in the mushroom were evaluated by AAS. The range of the accumulation factor was found to be 65-140, i.e., very marked. This finding suggests that the cultivation of P. ostreatus on substrates containing Hg from industrial and urban wastes could involve possible risks to human health.

Vasorelaxant properties of norbormide, a selective vasoconstrictor agent for the rat microvasculature.

1 The effects of norbormide on the contractility of endothelium‐deprived rat, guinea‐pig, mouse, and human artery rings, and of freshly isolated smooth muscle cells of rat caudal artery were investigated. In addition, the effect of norbormide on intracellular calcium levels of A7r5 cells was evaluated. 2 In resting rat mesenteric, renal, and caudal arteries, norbormide (0.5–50 μm) induced a concentration‐dependent contractile effect. In rat caudal artery, the contraction was very slowly reversible on washing, completely abolished in the absence of extracellular calcium, and antagonized by high concentrations (10–800 μm) of verapamil. The norbormide effect persisted upon removal of either extracellular Na+ or K+. The contractile effect of norbormide was observed also in single, freshly isolated smooth muscle cells from rat caudal artery. 3 In resting rat and guinea‐pig aortae, guinea‐pig mesenteric artery, mouse caudal artery, and human subcutaneous resistance arteries, norbormide did not induce contraction. When these vessels were contracted by 80 mM KCl, norbormide (10–100 μm) caused relaxation. Norbormide inhibited the response to Ca2+ of rat aorta incubated in 80 mM KCl/Ca2+‐free medium. Norbormide (up to 100 μm) was ineffective in phenylephrine‐contracted guinea‐pig and rat aorta. 4 In A7r5 cells, a cell line from rat aorta, norbormide prevented high K+‐but not 5‐hydro‐xytryptamine‐induced intracellular calcium transients. 5 These findings indicate that in vitro, norbormide induces a myogenic contraction, selective for the rat small vessels, by promoting calcium entry in smooth muscle cells, presumably through calcium channels. In rat aorta and arteries from other mammals, norbormide behaves like a calcium channel entry blocker.

Calcium‐antagonist effects of norbormide on isolated perfused heart and cardiac myocytes of guinea‐pig: a comparison with verapamil

Cardiac effects of norbormide and verapamil were compared in single ventricular myocytes, right atria, and Langendorff perfused hearts isolated from guinea‐pigs. In ventricular myocytes, norbormide 50 μm inhibited the peak calcium current (ICa) by 49.6±3.9% without altering the shape of the current‐voltage relationship; verapamil 1 μm inhibited ICa by 83.2±3.3%. Neither norbormide nor verapamil affected ICa at the first beat after a 3 min quiescence period; during repeated depolarizations, both drugs cumulatively blocked ICa (use‐dependence), with time constants of 23.0±7.0 s for norbormide and 91.3±8.4 s for verapamil. In constant‐flow perfused hearts electrically driven at 2.5 Hz or 3.3 Hz, both norbormide and verapamil concentration‐dependently decreased ventricular contractility (dP/dtmax), atrio‐ventricular (AV) conduction velocity and coronary pressure. Intraventricular conduction velocity was slightly decreased by norbormide but not by verapamil. At an equivalent change in AV conduction, norbormide depressed heart contractility less than verapamil. The effects of norbormide on AV conduction, intraventricular conduction, and contractility were frequency‐dependent. Furthermore, the curves correlating the mechanical and electrical effects of norbormide at the two frequencies used were apparently coincident, while those of verapamil were clearly separated. In spontaneously beating right atria, norbormide and verapamil decreased the frequency of sinus node (SA) in a concentration‐dependent way. At an equivalent effect on the AV conduction, norbormide exerted a greater effect on sinus frequency than verapamil. These results indicate that in guinea‐pig heart norbormide has the pharmacological profile of a Ca‐antagonist with strong electrophysiological properties. In comparison with verapamil, norbormide is more selective on SA and AV node tissues and exerts a weaker negative inotropic effect on ventricles. In principle, this pattern of effects may be an advantage in treating supraventricular tachyarrhythmias in patients with heart failure. The effect of norbormide on intraventricular conduction may represent an additional antiarrhythmic mechanism.

Are calcitonins analgesic and/or hyperalgesic?

The acetylcholine writhing test and the hot plate test were used in mice to evaluate peripheral and central analgesia after porcine, salmon and human calcitonin administrations. ICV and IV injection of calcitonins caused a peripheral analgesia that persisted for at least 2 hr. SC injection of calcitonins did not produce peripheral analgesia. However, when administered by IP route, an increasing peripheral analgesia was observed. Although it had a slow onset, it was as powerful as after ICV or IV administration. Employing the hot plate test to determine the entity of a central analgesic response, the IP administration of calcitonin surprisingly revealed a hyperalgesic effect. It started soon after the injection, reaching its maximum after about 2 hr. At this point the hyperalgesic effects were fully antagonized by EDTA.2 Na ICV, or by Ca++ICV. Moreover only the latter produced a strong and long acting analgesia. Applying a central or peripheral test, calcium seems to play different roles on the algesia variations induced by calcitonins.

Anthracene Based Compounds as New L-type Ca2+ Channel Blockers : Design, Synthesis, and Full Biological Profile

L-Type Ca(2+) channels (LTCCs) play a key role in the regulation of vascular smooth muscle contraction, and substances that interfere with their function (Ca(2+) channel blockers) are widely used in the therapy of hypertension. Here, we report anthracene-maleimide derivatives as new LTCC blockers. Among these, 3, lacking intracellular effects, was investigated in more detail. The results show that 3 binds preferentially to inactivated LTCCs, directly interacting with the pore-forming subunit of the channel.

RELAXANT AND CA2+ CHANNEL BLOCKING PROPERTIES OF NORBORMIDE ON RAT NON-VASCULAR SMOOTH MUSCLES

We have investigated the effects of the rat-specific vasoconstrictor agent norbormide on the mechanical and electrophysiological properties of rat non-vascular smooth muscles. Norbormide (50 microM) did not affect the resting tone of urinary bladder, tracheal, and duodenal rings. In all tissues, KCl-induced concentration-response curves were shifted downward by norbormide (5 and 50 microM). In urinary bladder and tracheal rings, norbormide inhibited contractile responses to carbachol only at the higher concentration (50 microM). In single gastric fundus myocytes, 50 microM norbormide inhibited L-type Ca(2+) current (I(Ca(L))) by about 60%, neither affecting both activation and inactivation rates of the current nor the current-voltage curve along the voltage axis. Our results indicate that rat non-vascular smooth muscles are relaxed by norbormide with a mechanism likely involving a reduction of Ca(2+) entry through L-type Ca(2+) channels.

AN IN VITRO METHOD FOR ASSESSING POTENTIAL TOXICITY OF COSMETIC PRODUCTS

AbstractOne difficulty encountered in testing finished cosmetic products arises from their final physical form. The presence of lipid or solid phases in the products makes them incompatible with the currently used cell culture media. In this study we have used a new method that permits the use of the testing materials directly on the cells monolayer using a cell culture insert (Falcon). This device is characterized by a polycarbonate porous membrane at the bottom of the insert. The insert containing the testing samples is put on top of the well and is then in contact with the medium. In this way we are still able, after the exposure, to evaluate several parameters that are indices of cell injury. We have tested the toxicity induced by four cosmetic emulsion bases using neutral red uptake determination, protein quantification, and lactate dehydrogenase activity on L929 cells. The least toxic emulsion was then used to estimate the toxicity of two commonly used preservatives, methylchloroisothiazolin-1 and ...

Analgesic properties of N-terminal substituted phenylalanyl-alanine

Phenylalanylalanine, an in vitro inhibitor of enkephalinase, and some of its N alpha-derivatives are shown to possess an analgesic action when injected i.p. and i.c.v. into mice in the presence or absence of Leu5-enkephalin. In the second case a synergistic response is observed. The intensity of the analgesic response depends markedly on the nature of the N-terminal substituent which affects the hydrophobic character of the resulting dipeptide, its subsequent transport and probably its rate of biotransformation by cleaving enzymes.

Therapeutic use of levocloperastine as an antitussive agent - An overview of preclinical data and clinical trials in adults and children

Cough associated with acute and chronic respiratory conditions is common in patients of all ages. Levocloperastine is a novel antitussive with a pharmacological profile distinct from that of the racemic DL-cloperastine. Levocloperastine with its dual mechanism of action acts on both the central bulbar cough centre and on peripheral receptors in the tracheobronchial tree. In preclinical studies, levocloperastine demonstrated antitussive effects similar to those observed with codeine. In acute and repeated-dose toxicity studies, levocloperastine was well tolerated in rodents and dogs, with no clinically significant cardiovascular or gastrointestinal adverse events. The pharmacokinetic behaviour of levocloperastine, best described by a two-compartmental model with absorption phase, is similar to that of the racemic compound DL-cloperastine. In clinical trials, levocloperastine had a faster onset of action and produced greater reductions in the intensity and frequency of cough compared with DL-cloperastine, codeine and levodropropizine. The antitussive effects (reduction in intensity and frequency of cough) of levocloperastine were observed after the first day of treatment in patients of all ages. In children, levocloperastine reduced night-time awakenings and irritability; in adults, it was also effective in treating ACE-inhibitor cough. Levocloperastine was generally well tolerated. There was no evidence of clinically significant central adverse events, whereas drowsiness, dry mouth and nausea were reported with comparator agents (levodropropizine, codeine, DL-cloperastine). Levocloperastine represents an effective alternative to currently used antitussive agents with the added advantage of faster onset of action and improved tolerability in all patient groups.