Piotr Wlaź

The involvement of serotonergic system in the antidepressant effect of zinc in the forced swim test.

Recent preclinical data indicated the antidepressant-like activity of zinc in different tests and models of depression. The present study investigates the involvement of the serotonergic system in zinc activity in the forced swim test (FST) in mice and rats. The combined treatment of sub-effective doses of zinc (hydroaspartate, 2.5 mg Zn/kg) and citalopram (15 mg/kg), fluoxetine (5 mg/kg) but not with reboxetine (2.5 mg/kg) significantly reduces the immobility time in the FST in mice. These treatments had no influence on the spontaneous locomotor activity. Moreover, while the antidepressant-like effect of zinc (5 mg/kg) in the FST was significantly blocked by pretreatment with inhibitor of serotonin synthesis, p-chlorophenylalanine (pCPA, 3x200 mg/kg), 5HT-2(A/C) receptor antagonist, ritanserin (4 mg/kg) or 5HT-1A receptor antagonist, WAY 1006335 (0.1 mg/kg), the zinc-induced reduction in the locomotor activity was not affected by these serotonin modulator agents. These results indicate the specific involvement of the serotonergic system in antidepressant but not the motion behavior of zinc in mice. Also, an increase in the swimming but not climbing parameter of the rat FST observed following zinc administration (2.5 and 5 mg Zn/kg) indicates the serotonin pathway participation. This present data indicates that the antidepressant-like activity of zinc observed in the FST involves interaction with the serotonergic system.

Antidepressant- and anxiolytic-like activity of magnesium in mice

The antidepressant- and anxiolytic-like effects of magnesium, an N-methyl-d-aspartate (NMDA) glutamate receptor inhibitor, were studied in mice using the forced swim test and elevated plus-maze test, respectively. The doses of 20 and 30 mg Mg/kg, reduced immobility time in the forced swim test exerting antidepressant-like activity. In the elevated plus-maze test, magnesium at the same doses produced anxiolytic-like effect. The doses of magnesium active in both tests did not affect locomotor activity. To evaluate the tolerance to these effects, we also performed experiments on the following acute/chronic magnesium treatment schedule: chronic saline and saline challenge at 0.5 h before behavioral experiments or serum magnesium determination (S+S), chronic saline and magnesium challenge (S+Mg), chronic magnesium and saline challenge (Mg+S), chronic magnesium and magnesium challenge (Mg+Mg). The antidepressant- and anxiolytic-like effect of magnesium was demonstrated in groups treated acutely and chronically with magnesium (Mg+Mg), but not in the Mg+S group. Moreover, these effects seem to be connected with at least 58% increase in serum magnesium concentration. The results indicate that magnesium induces the antidepressant- and anxiolytic-like effects without tolerance to these activities, which suggests a potential antidepressant and anxiolytic activity of magnesium in these disorders in humans.

NMDA/glutamate mechanism of antidepressant-like action of magnesium in forced swim test in mice.

Antidepressant-like activity of magnesium in forced swim test (FST) was demonstrated previously. Also, enhancement of such activity by joint administration of magnesium and antidepressants was shown. However, the mechanism(s) involved in such activity remain to be established. In the present study we examined the involvement of NMDA/glutamate pathway in the magnesium activity in FST in mice. In the present study we investigated the effect of NMDA agonists on magnesium-induced activity in FST and the influence of NMDA antagonists with sub-effective doses of magnesium in this test. Magnesium-induced antidepressant-like activity was antagonized by N-methyl-d-aspartic acid (NMDA). Moreover, low, ineffective doses of NMDA antagonists (CGP 37849, L-701,324, d-cycloserine, and MK-801) administered together with low and ineffective doses of magnesium exhibit significant reduction of immobility time in FST. The active in FST doses of examined agents did not alter the locomotor activity (with an exception of increased activity induced by MK-801). The present study indicates the involvement of NMDA/glutamate pathway in the antidepressant-like activity of magnesium in mouse FST and further suggests antidepressant properties of magnesium.

Anticonvulsant effects of the glycine/NMDA receptor ligands D-cycloserine and D-serine but not R-(+)-HA-966 in amygdala-kindled rats

1 The effects of the glycine/NMDA receptor partial agonists, d‐cycloserine and (+)‐HA‐966 and the full agonist, d‐serine, on focal seizure threshold and behaviour have been determined in amygdala‐kindled rats, i.e. a model of focal (partial) epilepsy. The uncompetitive NMDA receptor antagonist, MK‐801, was used for comparison. 2 The high efficacy glycine partial agonist, d‐cycloserine, did not alter the threshold for induction of amygdaloid afterdischarges (ADT) at doses of 20–80 mg kg−1 i.p., but significant ADT increases were determined after application of higher doses (160 and 320 mg kg−1). The ADT increases after these high doses were long‐lasting; significant elevations were still observed 2 days after drug injection. Determination of d‐cycloserine in plasma and brain tissue showed that it was rapidly eliminated from plasma. Compared to peak levels in plasma, only relatively low concentrations of d‐cycloserine were measured in brain tissue. 3 The low efficacy glycine partial agonist, (+)‐HA‐966, 10–40 mg kg−1 i.p., did not alter the ADT or seizure recordings (seizure severity, seizure duration, afterdischarge duration) at ADT currents. However, the drug dose‐dependently increased the duration of postictal behavioural and electroencephalographic depression in kindled rats. At the higher dose tested, postictal immobilization was dramatically increased from 3 min to about 120 min. This might indicate that glutamatergic activity is decreased postictally, which is potentiated or prolonged by (+)‐HA‐966. 4 Like d‐cycloserine, the glycine receptor full agonist, d‐serine, injected bilaterally into the lateral ventricles at a dose of 5 μmol, significantly increased the ADT, while no effect was seen at a lower dose (2.5 μmol). 5 The anticonvulsant effects observed with d‐cycloserine were completely antagonized by combined treatment with (+)‐HA‐966, indicating that the effects of d‐cycloserine were mediated by the glycine/NMDA receptor complex. 6 MK‐801, 0.1 mg kg−1, did not alter the focal seizure threshold or seizure recordings at ADT current, but induced marked phencyclidine(PCP)‐like behavioural alterations, such as hyperlocomotion, stereotypies and motor impairment. No PCP‐like behaviours were observed after d‐cycloserine, d‐serine or (+)‐HA‐966. High doses of (+)‐HA‐966 induced moderate motor impairment in kindled rats. 7 The long lasting increases in seizure threshold observed after the high efficacy glycine partial agonist, d‐cycloserine but not the low efficacy partial agonist, (+)‐HA‐966, may suggest that the effects of d‐cycloserine are mediated by adaptive changes in the NMDA receptor complex in response to glycine receptor stimulation. 8 Pharmacological intervention at the strychnine‐insensitive glycine receptor by high‐efficacy partial agonists with systemic bioavailability may be an effective means of increasing seizure threshold without concomitantly inducing PCP‐like adverse effects.

Effect of the glycine/NMDA receptor partial agonist, D-cycloserine, on seizure threshold and some pharmacodynamic effects of MK-801 in mice

Acute treatment of mice with D-cycloserine (a high efficacy, partial agonist at strychnine-insensitive glycine receptors) resulted in dose- and time-dependent increases in the threshold for electrically induced tonic seizures. This anticonvulsant effect was observed at doses which did not induce motor impairment, as determined by the rotarod test. Despite the relatively high intrinsic efficacy of D-cycloserine at glycine receptors, this drug did not produce proconvulsant effects in mice at any of the doses (5-320 mg/kg) or time points examined. Prolonged treatment with D-cycloserine led to a reduction of its anticonvulsant effect. Similar to D-cycloserine, the uncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist, MK-801 (dizocilpine), dose dependently increased the electroconvulsive threshold. Combined treatment with MK-801 and D-cycloserine led to significant anticonvulsant effects, but these effects were simply additive and not synergistic. In contrast to anticonvulsant activity, the motor impairing effect of MK-801 was markedly potentiated by D-cycloserine. The data substantiate that high efficacy glycine/NMDA receptor partial agonists such as D-cycloserine exert anticonvulsant activity at non-toxic doses. The finding that motor impairing but not anticonvulsant effects of MK-801 were potentiated by D-cycloserine suggests that different pharmacodynamic actions of NMDA receptor antagonists are differentially modulated by the glycine receptor, which could be related to the regional heterogeneity of the NMDA receptor complex in the brain.

Enhancement of antidepressant-like activity by joint administration of imipramine and magnesium in the forced swim test: Behavioral and pharmacokinetic studies in mice.

The effect of joint administration of imipramine (IMI) and magnesium (Mg) on antidepressant-like activity was studied in mice using forced swim test (FST). Mg doses ineffective per se (5 and 10 mg/kg) given jointly with IMI also at ineffective doses (10 and 15 mg/kg) resulted in a potent reduction in the immobility time. Since these combined treatments did not influence locomotor activity, the antidepressant-like activity was not due to non-specific behavioral activation. Moreover, we estimated the effect of joint administration of magnesium and IMI in FST on serum and brain magnesium, IMI and its active metabolite desipramine (DMI) concentrations in mice. Swim stress (mice subjected to FST) increased the magnesium concentration in serum and decreased it in the brain compared to naive animals. Moreover administration of IMI increased (normalized) magnesium brain concentration, without influence on the serum level. Joint administration of IMI and magnesium did not influence magnesium (compared with FST) or IMI and DMI (compared with IMI treatment alone) concentrations in both examined tissues. The present data demonstrated an enhancement of the antidepressant-like effect by joint administration of IMI and magnesium in the FST, and further indicate the particular role of magnesium in the antidepressant action. Since there was no increase in IMI, DMI or magnesium concentration after joint administration of magnesium and IMI, the data suggest that pharmacodynamic rather than pharmacokinetic interaction between magnesium and IMI is accountable for behavioral effect in the FST.

Magnesium in depression

Magnesium is one of the most essential mineral in the human body, connected with brain biochemistry and the fluidity of neuronal membrane. A variety of neuromuscular and psychiatric symptoms, including different types of depression, was observed in magnesium deficiency. Plasma/serum magnesium levels do not seem to be the appropriate indicators of depressive disorders, since ambiguous outcomes, depending on the study, were obtained. The emergence of a new approach to magnesium compounds in medical practice has been seen. Apart from being administered as components of dietary supplements, they are also perceived as the effective agents in treatment of migraine, alcoholism, asthma, heart diseases, arrhythmias, renal calcium stones, premenstrual tension syndrome etc. Magnesium preparations have an essential place in homeopathy as a remedy for a range of mental health problems. Mechanisms of antidepressant action of magnesium are not fully understood yet. Most probably, magnesium influences several systems associated with development of depression. The first information on the beneficial effect of magnesium sulfate given hypodermically to patients with agitated depression was published almost 100 years ago. Numerous pre-clinical and clinical studies confirmed the initial observations as well as demonstrated the beneficial safety profile of magnesium supplementation. Thus, magnesium preparations seem to be a valuable addition to the pharmacological armamentarium for management of depression.

Anticonvulsant effects by combined treatment with a glycineB receptor antagonist and a polyamine site antagonist in amygdala-kindled rats

Antagonists of binding sites within the NMDA receptor complex, i.e., L-701,324 (7-chloro-4-hydroxy-3-(3-phenoxy)phenyl-2(H)quinolone), a brain penetrating glycineB receptor antagonist, and ifenprodil, a polyamine site antagonist, were tested for anticonvulsant properties in fully amygdala-kindled rats, a model of limbic epilepsy. Both drugs were not able to significantly change seizure parameters (focal afterdischarge threshold, seizure severity, and duration of seizure and afterdischarges), when administered intraperitoneally up to doses which produced severe motor impairment. However, the combination of 10 mg/kg ifenprodil and 5 mg/kg L-701,324 had a pronounced anticonvulsant effect on afterdischarge threshold and seizure severity without concomitant increase of adverse effects. These findings support the hypothesis that drugs acting only at one site of the NMDA receptor complex are ineffective, while combinations of such drugs may synergistically act to suppress limbic seizures, thus providing an adequate strategy for the treatment of this type of refractory epilepsy.

Are neuronal nicotinic receptors a target for antiepileptic drug development? Studies in different seizure models in mice and rats

Altered function of neuronal nicotinic acetylcholine receptors in the brain has recently been associated with an idiopathic form of partial epilepsy, suggesting that functional alterations of these receptors can be involved in the processes leading to epileptic seizures. Thus, nicotinic acetylcholine receptors may form a novel target for antiepileptic drug development. In the present study, various nicotinic acetylcholine receptor antagonists, including novel amino-alkyl-cyclohexane derivatives, were evaluated in two animal models, namely the maximal electroshock seizure test in mice and amygdala-kindling in rats. For comparison with these standard models of generalized and partial seizures, the effects against nicotine-induced seizures were examined. Because some of the agents tested showed an overlap between channel blocking at nicotinic acetylcholine receptors and NMDA receptors, the potency at these receptors was assessed by using patch clamp in a hippocampal cell preparation. Preferential nicotinic acetylcholine receptor antagonists were potent anticonvulsants in the maximal electroshock seizure test and against nicotine-induced seizures. The anticonvulsant potency in the maximal electroshock seizure test was decreased by administration of a subconvulsant dose of nicotine. Such a potency shift was also seen with selective NMDA receptor antagonists, which were also efficacious anticonvulsants against both maximal electroshock seizures and nicotine-induced seizures. Experiments with agents combining nicotinic acetylcholine receptor and NMDA receptor antagonistic effects suggested that both mechanisms contributed to the anticonvulsant effect of the respective agents in the maximal electroshock seizure test. This was not found in kindled rats, in which nicotinic acetylcholine receptor antagonists exerted less robust effects. In conclusion, it may be suggested that nicotinic acetylcholine receptor antagonism might be a valuable therapeutic approach to treat generalized epileptic seizures but rather not complex partial seizures.

Inhalable highly concentrated itraconazole nanosuspension for the treatment of bronchopulmonary aspergillosis

Cystic fibrosis (CF) patients are suffering from multiple often chronic endobronchial infection. The stiff mucus in these patients represents a compartment, which cannot easily be reached by systemic treatment. While bacterial infections are now successfully treated with repeated inhalation of antibiotics such as tobramycine, 57% of CF patients are colonized by Aspergillus species. About 10-20% of colonized patients develop symptoms of allergic bronchopulmonary aspergillosis (ABPA). While current standard of treatment of ABPA in CF patients is to suppress the allergy related symptoms by administration of glucocorticoids, itraconazole (ITRA), administered orally at high doses, can alleviate the symptoms of ABPA. However, no inhalable formulation of ITRA is available to enable local treatment of aspergillosis. The aim of this study was to describe an aqueous nanosuspension of ITRA and to characterize the pharmacokinetics after single dose inhalation. Using wet-milling with organic milling beads, a stable nanosuspension with particle size in the range of 200nm and an ITRA concentration of 20% (v/w) could be obtained, using polysorbate 80 at a concentration of 14% relative to ITRA. The suspension was stable if stored at 8°C for 3 months without particle growth and could be nebulized using standard nebulizer technologies including mesh technology and pressured air nebulizers. A 10% suspension was well tolerated upon repeated dose inhalation once daily for 7 days at a predicted dose of 45mg/kg in rats. A single dose inhalation at a predicted dose of 22.5mg/kg resulted in maximum lung tissue concentration of 21.4μg/g tissue with a terminal half-life of 25.4h. Serum concentrations were lower, with a maximum concentration of 104ng/ml at 4h after dosing and a terminal half-life of 10.5h. The data indicate that ITRA nanosuspension represents an interesting formulation for inhaled administration in CF patients suffering from ABPA. High and long lasting lung tissue concentrations well above the minimal inhibitory concentration of Aspergillus species enable once daily administration with minimal systemic exposure.