MPP(+)-induced mitochondrial dysfunction is potentiated by dopamine

MPP(+), the major metabolite of the Parkinsonism-inducing compound MPTP, responsible for the destruction of the nigrostriatal pathway in primates and rodents, has been assayed in isolated rat liver mitochondria in the presence of physiological concentrations of dopamine or analogous concentrations of melanin-dopamine. 5 microM MPP(+) in the presence of 70 microM dopamine or melanin-dopamine, but not alone, decreased the heat production and oxygen consumption of a mitochondrial suspension activated with succinate and ADP. Both dopamine and oxidized dopamine plus MPP(+) also decreased the mitochondrial reductive power measured with MTT. Mitochondrial swelling was observed, associated with an increase in membrane mitochondrial potential, as a synergistic effect between low concentrations of MPP(+) and dopamine. It is suggested that cytosolic dopamine, by itself or via its autooxidation products, may play a relevant role in the mitochondrial toxicity of MPP(+). A failure in the regulation of the storage/release of dopamine could aggravate a mitochondrial damage and trigger the neurodegenerative process underlying MPTP toxicity and Parkinson's disease.

Effect of naloxone on behavioral changes induced by subchronic administration of ethanol in rats

Endogenous opioid peptides appear to be involved in acute behavioral effects induced by single doses of ethanol. However, its role in repeated ethanol exposure has not been studied. In the present study ethanol was given to rats at the doses of 2 and 4 g/kg by a stomach gauge for 15 days, and its effects on spontaneous motility, open-field activity, and active avoidance behavior recorded on the 3rd, the 6th and the 15th days. Then the effect of naloxone (0.5 and 2 mg/kg by intraperitoneal route) was tested against a challenge ethanol dose, administrated by oral route, on the 16th day. Control animals received tap water and saline instead of ethanol or naloxone, respectively. Both doses of ethanol induced a decrease in spontaneous motility that was antagonized by naloxone. Open-field ambulations were increased by the high dose of ethanol, low-dose lacking effect; naloxone did not modify these ethanol effects. The low dose of ethanol shortened latency time in shuttlebox, the high dose causing escape and freezing responses; none of these effects were modified by naloxone. Therefore, endogenous opioid peptides appear to play a limited role in the chronic effects of ethanol in rats; particularly its effects in tests inducing an increase in the level of anxiety were resistant to naloxone.

Determination of polyethylene glycol activated with cyanuric chloride in liposomes

A simple method was developed for the determination of polyethylene glycol (PEG) 5000 activated with cyanuric chloride attached or adsorbed to the liposome membrane. The procedure is based in the measurement of the absorbance at 234 nm of the triazine ring of cyanuric chloride after disrupting the liposomal structure with CHCl3/MeOH (1/8, v/v). In this medium, the molar absorptivity of the molecule is the highest, and lipid does not interfere with the measurement. This procedure results in a convenient, sensitive, and rapid method for the determination of this kind of activated polyethylene glycol in liposomes. The minimal concentration of PEG measured is 50 microM, and so the method is sufficiently sensitive to quantify PEG 5000 in the minimal amounts used for protecting the liposomes from the action of serum. Values calculated by this method have been compared with those obtained by 1H NMR, and a good correlation between them has been obtained.

[Continuous epidural perfusion with meperidine on demand for the treatment of postoperative pain]

OBJECTIVE

To determine whether epidural administration of meperidine through a system affording patient-controlled analgesia (PCA) is appropriate for postoperative pain.

PATIENTS AND METHODS

A prospective double-blind study of 30 patients undergoing high abdominal surgery randomly into two groups. After surgery with the same type of general anesthesia for both groups, group A received epidural meperidine through a PCA pump (initial boluses of 50 mg + infusion of 10 mg/h with additional doses of 25 mg upon patient demand and closure time of 90 min). Control group B received 0.9% saline serum through an epidural PCA system with identical perfusion characteristics. All patients had access to additional analgesia with subcutaneous meperidine (1 mg/kg weight).

RESULTS

There was a wide interindividual variation in meperidine consumption in group A, with a mean total dose of 301.4 +/- 73 mg in 24 hours and no patient requiring additional subcutaneous meperidine. Subcutaneous meperidine required in group B reached 273 +/- 65.8 mg in 24 hours, with no significant differences between groups A and B for total dose given. No side effects inherent to the technique were found. Sufficient control of pain was achieved for all patients receiving epidural meperidine.

CONCLUSIONS

Epidurally administered PCA with meperidine affords better pain relief with greater patient satisfaction than the same amount of drug given subcutaneously in successive doses upon patient request.

Diuretic action of an aqueous extract of Lepidium latifolium L

An aqueous extract of Lepidium latifolium L. given orally and intraperitoneally considerably enhanced urinary excretion (UV) in rats with respect to control groups. A slight increase in ion excretion was also observed. Other parameters such as specific gravity, nitrite, pH, glucose, ketone bodies, urobilinogen, and blood were also studied. A good correlation for the dosage rat/man for the aqueous extract was achieved.

Inhibitory and contractile effects of okadaic acid on rat uterine muscle

The effects of okadaic acid and its interactions with various agents known to increase, by different mechanisms, the intracellular levels of cyclic AMP and/or cyclic GMP were investigated in isolated strips of rat myometrium. Okadaic acid showed inhibitory effects at concentrations between 10(-7) M and 3 x 10(-6) M. At higher concentrations, a biphasic, contractile and then relaxant response was observed. The results obtained suggest that, in rat uterine smooth muscle, the inhibitory effects of okadaic acid are not entirely mediated by the activation of cyclic AMP- and/or cyclic GMP-dependent pathways. The data also point to the existence of a clear interaction between okadaic acid and methylxanthines, although further studies are needed to clarify the mechanisms involved in this interaction.

Therapeutic effects of hidrosmin on chronic venous insufficiency of the lower limbs

A double-blind, placebo-controlled trial was carried out to assess the effectiveness of a new synthetic bioflavonoid, hidrosmin, in patients with chronic venous insufficiency of the lower limbs. Fifty-seven patients, showing varicose veins and ankle swelling and suffering from local pain and heaviness of the legs, were allocated at random to receive treatment for 45 days with 1 capsule 3-times daily of either 200 mg hidrosmin (30 patients) or placebo (27 patients). Pain and heavy legs were assessed using rating scales; swelling was assessed by a photographic method. The results showed that hidrosmin produced a significant clinical improvement in all of the parameters evaluated; compared with placebo, there was a marked reduction in the main subjective symptoms accompanied by a 10% reduction in swelling. Apart from 1 patient who complained of epigastric pain, there were no reports of adverse events during the study period.

Effect of ethanol on insulin-stimulated glucose uptake in the isolated rat diaphragm

Insulin-stimulated (0.16 and 2.56 nM) glucose uptake (GU) was studied in isolated rat diaphragms in the presence of ethanol (EtOH) 21, 42 and 84 mM as well as in diaphragms removed from rats orally treated with the drug (1.5 or 4.5 g/kg/day) for 10 or 30 days. In spite of inhibiting the base-line GU, the addition of EtOH to the incubation medium gave rise to a potentiation of the insulin effect. In the orally intoxicated series, the low-dose EtOH increased the response to 0.16 nM insulin after 10 or 30 days, no changes being observed in that induced by 2.56 nM insulin. On the other hand, the high-dose EtOH caused an increase of the base-line GU which remained practically unmodified in the presence of insulin. The precise molecular basis for these phenomena is unknown.

Pharmacological study of the muscle paralyzing activity of the juice of the banana trunk

Extracts of the juice of the banana trunk were assayed in the isolated phrenic nerve-diaphragm muscle preparation of the rat. The chemical composition of those producing muscular paralysis was then studied. As active extracts mainly consisted of monopotassium oxalate, the effect of this compound on the muscle preparation was investigated and compared with that of the active extracts. The pattern of muscular paralysis induced by monopotassium oxalate was the same as that seen with the juice extracts. Likewise inhibition of contractions of the tibialis muscle was observed in vivo after intra-arterial administration of both the crude concentration of the juice and monopotassium oxalate. These findings suggest that monopotassium oxalate could be responsible for the muscular paralysis caused by the juice of banana trunk.

Clindamycin vs penicillin for anaerobic lung infections. High rate of penicillin failures associated with penicillin-resistant Bacteroides melaninogenicus

Thirty-seven adult patients with anaerobic lung infections (27 lung abscesses and 10 necrotizing pneumonias) were submitted to transthoracic needle-aspiration and/or bronchoscopic specimen brush cultures before therapy and thereafter in all cases considered to be failures. Patients were randomly assigned to receive either clindamycin, 600 mg intravenously every 6 hours, or penicillin G, 2 million U every 4 hours for no less than 8 days, until clinical and radiological improvement became apparent. Treatment was continued orally with clindamycin, 300 mg every 6 hours, or penicillin V, 750 mg every 6 hours, until completing a minimum of 4 weeks. Ten of the 47 anaerobes initially isolated from the lung (nine Bacteroides melaninogenicus and one Bacteroides capillosus) were resistant to penicillin, but none were resistant to clindamycin. Five of the nine patients harboring these penicillin-resistant Bacteroides received penicillin, and all failed to respond to therapy. Overall, eight of the 18 patients in the penicillin group and one of 19 in the clindamycin group failed to respond to therapy. These drugs were equally well tolerated in both groups. The presence of penicillin-resistant Bacteroides is a frequent cause of penicillin failure in patients with anaerobic lung infections. In this setting, clindamycin appears to be the current therapy of choice for initial treatment.

Naloxone potentiation of cardiovascular responses to sympathomimetic amines in the rat

The work was aimed at analyzing the ability of naloxone to potentiate 1) the arterial pressure responses to sympathomimetic amines administered i.v. in normotensive anesthetized, pithed, chemically sympathectomized or acutely adrenalectomized rats and 2) the chronotropic responses to norepinephrine in the isolated rat atria. In anesthetized rats, naloxone (2.5-10 mg/kg i.v.) potentiated the pressor responses to epinephrine (2 micrograms/kg). Naloxone (5 mg/kg) significantly potentiated the pressor responses to norepinephrine (1-4 micrograms/kg), phenylephrine (10-50 micrograms/kg) and the reflex pressor responses to a 60-sec carotid occlusion. On the contrary, naloxone did not potentiate the arterial pressure responses to methoxamine (100 micrograms/kg), angiotensin (0.5-2 micrograms/kg) and isoproterenol (1 micrograms/kg). Pithing or acute adrenalectomy did not alter the naloxone-induced potentiation of the pressor responses to norepinephrine (0.125-0.5 micrograms/kg). 6-Hydroxydopamine pretreatment abolished completely the naloxone-induced potentiation of the pressor responses to norepinephrine (0.25-1 micrograms/kg). In isolated rat atria, naloxone (1.4 and 2.8 x 10(-5) M) potentiated the chronotropic responses to norepinephrine (1.5-6 x 10(-8) M). It is suggested that naloxone potentiates cardiovascular responses to sympathomimetic amines by interacting with presynaptic adrenergic mechanisms which could additionally contribute to its pressor effects in acute hypotensive conditions.

Chronic amitriptyline decreases autotomy following dorsal rhizotomy in rats

In the rat, unilateral dorsal cervicothoracic rhizotomy (C5-T1), a proposed model of chronic pain, resulted in autotomy of the ipsilateral limb. The self-mutilation lesions were evaluated daily by means of an autotomy score from the 1st to the 80th postoperatory day. The onset of lesions was variable and attained the maximum degree 8-9 weeks after the dorsal roots section. Chronic administration of amitriptyline (5 and 10 mg/kg/day, i.p., over 30 days), started on the 10th day after rhizotomy, decreased autotomy behavior, an effect which persisted 20 days after treatment withdrawal, and lengthened almost two-fold the lag time between rhizotomy and appearance of lesions. A more pronounced effect was observed with the lowest dose of amitriptyline suggesting the existence of a therapeutic window. Possible mechanisms for the antinociceptive effect of amitriptyline in this model are discussed.

Naloxone-induced increase in blood and brain ethanol concentrations in rats

Although a reduction in blood ethanol concentration has been proposed to mediate the ethanol antagonist activity of naloxone observed in clinical and experimental situations, an increase in this variable as well as in brain ethanol concentration has been found in rats treated with naloxone (0.5 and 2.0 mg/kg, i.p.) ten min after intragastric administration of ethanol (1 and 2 g/kg). This effect disappeared either when naloxone was administered 50 min after ethanol or when ethanol was given intraperitoneally. On the other hand, naloxone induced a slight but significant slowing in intestinal transit rate. These results suggest that naloxone may facilitate gastrointestinal absorption of ethanol when administered soon after an oral load of this drug. Therefore, mechanisms other than a pharmacokinetic interaction appear to be involved in the antagonist action of naloxone.

Antagonism of the stimulant and depressant effects of ethanol in rats by naloxone

The action of naloxone (0.5 and 2 mg/kg IP) on the behavioural effects of a low (2 g/kg PO) and a high dose (4 g/kg PO) of ethanol was studied in rats. Ethanol at the low dose increased spontaneous motility, enhancing open-field external ambulations and reducing shuttle-box latency. All these effects were antagonized by naloxone. Ethanol at the high dose produced by hypomotility, decreasing open-field external ambulations and impairing shuttle-box performance. In this case, naloxone also reduced the ethanol effect, but its action was less consistent. Therefore, although mechanisms other than a specific opioid receptor blockade by naloxone must be considered, an involvement of opioid peptides in the effects of ethanol cannot be discounted.

Effects of dopaminergic agonists and antagonists on the partially contracted, isolated and perfused renal artery of the rat

The effects of two dopamine agonists, dopamine itself and SKF 38393, alone and in the presence of several dopamine antagonists, have been studied in the partially contracted, isolated and perfused renal artery of the rat. In this preparation, earlier used by other authors in vascular pharmacological experiments, the dopaminergic agents produced clear vasodilator effects which were inhibited by all antagonists used. Due to its low cost and simplicity, such a preparation would be of practical value in testing dopaminergic drugs.

Effect of ethanol on neuromuscular function in rats. Its interaction with alcuronium

The effect of chronic ethanol intake on neuromuscular function has been analyzed by using a rat tibial muscle preparation. The time-course of single twitches, trains-of-four, tetanus and post-tetanic facilitation with and without blockade with alcuronium was evaluated. A decrease in these parameters was observed, being more pronounced in ethanol fed rats during 10 than 30 days. The twitch was the most affected parameter. After recovery of alcuronium blockade, the depressant effects of ethanol were completely reversed. These data suggest that low but sustained ethanol blood levels causes evident alterations of neuromuscular function due, probably, to a postjunctional action.

Pharmacological study of uzarigenin-glucoside-canaroside

Uzarigenin-glucoside-canaroside (UGC) is a steroid glycoside isolated from the leaves of ISOPLEXIS CHALCANTHA whose pharmacological properties have not been so far studied. In this paper the effect of UGC on isolated auricle of rabbits, urinary excretion of rats, isolated jejunum of rabbits, (86)Rb (+) uptake by erythrocytes as well as its emetic effect in pigeons are presented, using digoxin as standard. The pharmacological activity of UGC was similar to that of digoxin, UGC possessing, however, a lesser vomiting action.

Phytochemical Study of Isoplexis chalcantha

Three cardioactive glycosides were isolated from ISOPLEXIS CHALCANTHA. Two were identified as uzarigenin-canarobioside and uzarigenin-digilanidobioside, previously found in other Isoplexis. The third glycoside must be uzarigenin-digitoxoside from the same source. The flavones apigenin, luteolin and their 7- Obeta- D-glycosides were also obtained, together with the salidroside [2-(4-hydroxyphenyl)-ethyl-1-beta- D-glucopyranoside].

Postjunctional Origin of the indirect-like sympathomimetic effect of metanephrine and normetanephrine on blood pressure

The effects of metanephrine and normetanephrine have been compared with those from equiactive doses of the origin compounds, adrenaline and noradrenaline, on the pressor responses in rat, in order to determine whether their effects are owed, at least partially, to a releasing presynaptic action of the catecholamines in normal animals as well as those pretreated with reserpine, guanethidine and 6-OH-dopamine. Their effects have likewise been studied in isolated perfused renal arteries both in normal and reserpinized rats. None of the adrenolytic agent used were able either to reduce the duration of the hypertensive response or to accelerate tachyphylaxis. Identical results were obtained in renal artery preparations. It is thus concluded that the catecholamines stored in presynaptic endings are not involved in the observed phenomena and it is suggested that they might depend on the high doses required to produce effects equiactive to those of the origin substances.

Effect of Anesthesia on rat respiration. A study in decerebrated, decerebrated-anesthetized and intact-brain preparations

The time course of respiratory parameters and blood pressure was studied in decerebrated rats (DR), decerebrated rats treated with a combination of thiopental plus urethane (DAR), and intact brain rats anesthetized with the same combination (IBAR). Moreover, the respiratory sensitivity to a stimulating dose of amphetamine was tested in the three preparations. DR exhibited a spontaneous and steady increase of ventilation which was absent in DAR. A steady increase of ventilation was also observed in IBAR, although of a lesser intensity. Amphetamine induced a clear respiratory stimulation which was decreased by the administration of anesthetics. A tendency to hypotension was seen in all animals. Therefore, the respiratory instability and the decreased pharmacological response observed in the presence of anesthetics are important factors to be considered when interpreting results obtained in this kind of preparations.

Ethanol and receptor function

The effects of ethanol in vitro (21 and 42 mM) and in vitro (10 and 30 days of exposure) on the dose:effect curves for noradrenaline and acetylcholine in isolated auricles and uterus of rats, respectively, have been studied. Likewise, the acetylcholine-atropine interaction was studied in rat uterus under the above-mentioned conditions. Analysis of theoretical curves as well as pD2 and pA2 calculations revealed that ethanol causes changes in the tissue responses to the agents assayed which in turn may be an expression of modification in the receptor function.