Protective Effects Of Diazepam Research Articles

Influence of etoricoxib on anticonvulsant activity of phenytoin and diazepam in experimental seizure models in mice

Our aim was to investigate the effect of etoricoxib on the anticonvulsant activity of phenytoin and diazepam against seizure models in mice. In addition the acute adverse effect of etoricoxib was assessed with a chimney test. The maximal seizure pattern was induced in mice by giving an alternating current of 50 mA for 0.2 s, while chemical seizures were induced by intraperitoneal injection of pentylenetetrazole at its CD97 dose (97% convulsive dose for the clonic phase). Test drug was administered 45 min before the electrical or chemical induction of seizures in combination with conventional antiepileptics. The ability of the test drug to reduce or abolish the extensor phase of maximal electroshock and clonic-type seizures in the chemical induction method was selected as anti-seizure criteria. Concurrent treatment with etoricoxib at an oral dose of 10 mg/kg reduced the anticonvulsant potency of phenytoin. The protective effects of diazepam against pentylenetetrazole-induced convulsions was significantly increased and the mortality rate was reduced by concurrent treatment with etoricoxib (10 mg/kg p.o.) when compared with diazepam groups. No neurotoxic effect was observed with etoricoxib (10 mg/kg p.o.) and it had no impact on motor coordination in the chimney test in mice. Etoricoxib applied at its highest dose (10 mg/kg) significantly enhanced the free plasma levels of diazepam whereas the free plasma levels of phenytoin were significantly reduced. The obtained results suggest that the preferential cyclooxygenase-2 inhibitor etoricoxib significantly reduced the anticonvulsant action of phenytoin and significantly increased the beneficial action of diazepam against maximal electroshock and pentylenetetrazole-induced convulsions in a mouse model.

Diazepam neuroprotection in excitotoxic and oxidative stress involves a mitochondrial mechanism additional to the GABA AR and hypothermic effects

The aim of the present investigation was to analyze the molecular mechanism(s) of diazepam neuroprotection in two models of selective neuronal death in CA1 sector of hippocampus: in vivo following transient gerbil brain ischemia and in vitro in rat hippocampal brain slices subjected to glutamatergic (100 μM NMDA) or oxidative (30 μM tertbutyl-hydroksyperoxide (TBH)) stress. In the in vivo model the diazepam treatment (two doses of 10 mg/kg i.p. 30 and 90 min after the insult) resulted in more than 60% of CA1 hippocampal neurons surviving the insult comparing with 15% in untreated animals. To test whether the protective effect of diazepam was due to the postulated drug-induced hypothermia we followed the fluxes of body temperature during postischemic reperfusion: diazepam reduced temperature from 36.6 ± 1 °C to 33.4 ± 2 °C. Equivalent hypothermia induced and maintained in animals after ischemia did not prevent neuronal cell loss to the same extent as diazepam did (42.8 ± 9.2% and 72.4 ± 14.5% of live neurons, respectively). In vitro, under constant temperature conditions, diazepam exerted neuroprotective effects following a “U-shaped” dose–response curve, with concentration efficacy window of 0.5–10 μM. Five micro-molar diazepam showed significant protection by reducing over 50% the number of (dead) propidium iodide labeled cells even in the presence of GABA A receptor antagonist bicuculline. Next, we have shown that diazepam reduced the efflux of cytochrome c out of mitochondria both in compromised CA1 neurons in vitro and in isolated mitochondria treated with 30 μM THB. Our results suggest that the neuroprotective action of diazepam relies on additional mechanism(s) and not solely on its hypothermic effect. We suggest that diazepam evokes neuroprotection through its central receptors located on the GABA A receptor complex and, possibly, through its peripheral receptor, the translocator protein TSPO (previously called the peripheral benzodiazepine receptor) located in the outer mitochondrial membrane.

EFFECT OF ALCOHOL-WITHDRAWAL ON PENTYLENETETRAZOL-INDUCED SEIZURES IN RATS: A PROTECTIVE FUNCTION OF VITAMIN C

Oxidative injury in the brain has been suggested as a common pathway of several neurologic diseases including epilepsy. Pentylenetetrazol (PTZ)-induced seizure is a proposed animal model of epilepsy. Further, animals have been shown to exhibit a PTZ-like stimulus after cessation of chronic alcohol treatment. The purpose of the present study is to further investigate the effect of alcohol withdrawal on acute PTZ-induced seizures, and the possible protective function of vitamin C. Seventy male rats were randomly allocated to control (saline-injected) and alcohol-treated groups. Animals were divided into seven groups, 10 animals each. Group 1, animals were injected with normal saline (0.9%), i.p., daily for two weeks. Other groups (Groups 2-7) were treated with ethyl alcohol (20% w/v) at a dose of 2 gm/kg body weight, i.p., daily for two weeks. Group 3, animals were pretreated with Vitamin C at a dose of 400 mg/kg body weight one hour before each alcohol injection. Group 4, animals were pretreated with Diazepam at a dose of 1 mg/kg body weight one hour before PTZ injection. Group 5, animals were pretreated with Vitamin C at a dose of 400 mg/kg body weight one hour before each alcohol injection; in addition, animals were pretreated once with Diazepam at a dose of 1 mg/kg body weight, i.p., one hour before PTZ injection. Group 6, animals were pretreated with Diazepam at a dose of 0.5 mg/kg body weight one hour before PTZ injection. Group 7, animals were pretreated with Vitamin C at a dose of 400 mg/kg body weight one hour before each alcohol injection; in addition, animals were pretreated once with Diazepam at a dose of 0.5 mg/kg body weight, 1.p., one hour before PTZ injection. All groups were treated acutely with PTZ at a dose of 30 mg/kg body weight, i.P., One day after the last injection of saline or alcohol. Seizures were evaluated using the modified Racine's scale. The undetected effects of the subconvulsive dose of PIZ (30 mg/kg) was clearly observed in alcohol-withdrawing animals Pretreatment with Vitamin C alone could not prevent PIZ-induced seizures. In contrast, Diazepam (1 mg/kg) could decrease seizures score. This protective effect of diazepam has dissipated upon dose reduction (DZP, 0.5 mg/kg). However, the combined effects of Diazepam (0.5 mg/kg) and Vitamin C (400 mg/kg) proved to be effective in suppressing the convulsant effect of PTZ in alcohol-withdrawing animals. It is concluded that alcohol withdrawal enhanced the sensitivity of animals to the acute convulsant effects of PTZ. Vitamin C could not block seizure activity, however, it enhanced the anticonvulsant effects of diazepam.

NG-Nitro- l-arginine impairs the anticonvulsive action of ethosuximide against pentylenetetrazol

N G-nitro- l-arginine (NNA; an inhibitor of nitric oxide synthase) in a dose of 40 mg/kg impaired the protective activity of ethosuximide against the clonic phase of pentylenetetrazol-induced seizures in mice. The ED 50 value of ethosuximide was significantly increased from 108 to 158 mg/kg. NNA (40 mg/kg) was ineffective against the protective effects of diazepam, phenobarbital and valproate against pentylenetetrazol-induced seizures. NNA (40 mg/kg) did not influence the plasma levels of the antiepileptic drugs studied, so a pharmacokinetic interaction is not probable. l-Arginine (500 mg/kg) prevented the NNA-induced reduction of the anticonvulsive activity of ethosuximide. It can be concluded that nitric oxide participates in the expression of the anticonvulsive action of ethosuximide, but not that of diazepam, phenobarbital and valproate, against pentylenetetrazol-induced seizures.

The effect of chronic cyclodiene insecticide treatment on some pharmacological actions of diazepam in rats

The sedative and hypnotic effects of diazepam were tested in rats following chronic treatment with subconvulsive doses of the cyclodiene insecticides, endosulfan and aldrin. The anticonvulsant effect of diazepam was determined on picrotoxin-induced convulsions in insecticide-treated and control animals. Both endosulfan and aldrin promoted the convulsant action of picrotoxin indicating that the insecticides were able to show proconvulsant action following chronic administration. Interestingly, the protective effect of diazepam against picrotoxin-induced convulsions was greater in endosulfan- and aldrin-treated animals than in control animals. The sedative and hypnotic effects of diazepam were also increased in insecticide-treated animals. The mechanisms involved in the interaction were discussed with the support of the findings reported by the present and other investigators on the central and hepatic effects of chronic endosulfan and aldrin treatment.

Ethanol prevents stress-induced increase in cortical DOPAC: Reversal by RO 15–4513

Electric foot-shock increased DOPAC and decreased DA levels by about 70 and 20% respectively in the medial prefrontal cortex in rats. Pretreatment with diazepam (5 mg/kg IP) or ethanol (1.2 g/kg orally) prevented these stress-induced changes. The protective effect of diazepam and ethanol was eliminated by RO 15–4513 (5 mg/kg IP) a partial inverse benzodiazepine agonist.

The specific protective effect of diazepam and valproate against isoniazid-induced seizures is not correlated with increased GABA levels

Amino acid concentrations were measured in the cortex, cerebellum and hippocampus of the mouse brain before and during seizures induced by isoniazid (250 mg/kg i.p.), an inhibitor of L-glutamate-1-decarboxylase (EC 4.1.1.15: GAD). Valproate sodium and diazepam dose-dependently delay the onset of convulsive fits caused by isoniazid. However, neither diazepam nor valproate prevented the decrease in GABA concentrations produced by isoniazid alone. Also, these antiepileptic drugs did not modify the rate of GABA depletion elicited by isoniazid. These results, observed in four different brain structures, strengthen those first obtained with beta-vinyllactic acid, another inhibitor of GAD.

Involvement of a GABAergic mechanism in the anticonvulsant effect of pentobarbital against maximal electroshock-induced seizures in rats

The interaction between pentobarbital and other modulators of GABAergic transmission (diazepam, ethanol and progabide) was investigated on maximal electroshcok seizures and on the loss of righting reflexes in rats. Pentobarbital, diazepam and ethanol produced a dose-dependent protection against electroshock seizures, with pentobarbital being more potent (3- and 50-times) than diazepam and ethanol. Progabide neither provided protection nor caused loss of righting reflex. Subprotective doses of pentobarbital and diazepam, together or when combined with a single ineffective dose of ethanol or progabide, caused protection against seizures and loss of righting reflex for variable durations, while ethanol and progabide combination did not provide protection. The protective effect of diazepam was antagonized by RO15-1788, picrotoxin and bicuculline pretreatments. The antagonism of pentobarbital protection by a specific GABA receptor antagonist, bicuculline suggests involvement of the GABAergic system in the anticonvulsant effect of pentobarbital. These results indicate that, like diazepam, the anticonvulsant effect of pentobarbital appears to be mediated through a GABAergic mechanism.

Protective effects of diazepam and valproate on β-vinyllactic acid-induced seizures

GABA level and the activity of l-glutamate-1-decarboxylase (GAD) (EC 4.1.1.15) were studied in brains of mice treated with β-vinyllactic acid, a new, selective and pyridoxal phosphate-independent GAD inhibitor. Valproate and diazepam protected mice against convulsions caused by β-vinyllactic acid although both anti-epileptic drugs antagonized neither the decrease in GABA concentrations nor the inhibition of GAD observed after treatment with β-vinyllactic acid alone. Assuming that the anticonvulsant effect measured with both antiepileptics is GABA mediated, these results support the hypothesis of a postsynaptic enhancement of GABAergic transmission by diazepam and valproate.

Pyrethroid toxicology: Protective effects of diazepam and phenobarbital in the mouse and the cockroach

Diazepam delayed the onset of action of deltamethrin and fenvalerate (pyrethroids producing the Type II syndrome) but not of permethrin and allethrin (pyrethroids producing the Type I syndrome) in both the mouse and cockroach. Phenobarbital was less potent as an anticonvulsant and also less selective since it delayed the onset of signs for both deltamethrin and permethrin in each animal. In vivo extracellular nerve recordings in the cockroach showed differences between deltamethrin and permethrin in the nerves responding, the types of response, and the protective effect of diazepam. A 3 mg/kg ip dose of diazepam protected the mouse against mortality due to a subsequent intracerebroventricular dose of either deltamethrin or permethrin, increasing their LD 50 values by six- to ninefold. Possible mechanisms for the Type II pyrethroid syndrome include an action at the GABA receptor complex or a closely linked class of neuroreceptor, or through depolarization of nerve terminals.

Effects of some antiepileptic drugs in pentetrazol-induced convulsions in mice lesioned with kainic acid.

Mice were injected with intracerebroventricular (i.c.v.) kainic acid (KA; 0.1 micrograms per animal) and the pentetrazol test was carried out on the fifth day after the administration of the amino acid. The following antiepileptic drugs were tested for anticonvulsant activity in mice lesioned with KA: diazepam (0.4 mg/kg), phenobarbital (12.5 and 25 mg/kg), trimethadione (200 and 400 mg/kg), depakine (200 and 400 mg/kg), carbamazepine (10 and 20 mg/kg), lefadol (bromophenylsuccinimide; 20 mg/kg), and acetazolamide (320 mg/kg). All drugs were given intraperitoneally, except for carbamazepine, which was also given orally in doses of 100 and 200 mg/kg. Pentetrazol was administered subcutaneously in a dose of 110 mg/kg, and the animals were subsequently observed for the occurrence of clonic and tonic convulsions within 30 min. The protective effects of diazepam and phenobarbital were significantly reduced in the KA-lesioned animals, while the actions of the remaining anticonvulsants were unaltered. Moreover, a substantial loss of pyramidal cells in the CA 3 field of the hippocampus was noted after i.c.v. injection of KA. It may therefore be concluded that the mechanism of the action of diazepam and phenobarbital are partially dependent on the intact functions of the hippocampal formation.

Decreased convulsant potency of picrotoxin and pentetrazol and enhanced [ 3H]flunitrazepam cortical binding following stressful manipulations in rats

Various stressful manipulations in rats (cold-water swim, electric foot-shock administration, impaired access to food reward) were found to reduce the convulsant potency of drugs which interfere with GABA or benzodiazepine central processes. The convulsant threshold dosages of picrotoxin (0.4 mg/ml) or pentetrazol (10 mg/ml) administered after the stress by infusion (0.2 ml/min) via a vein of the tail were enhanced. The onset of generalized seizures induced by isoniazid (800 mg/kg) or by thiosemicarbazide (64 mg/kg) i.p. was delayed after cold-water swim. However, convulsant threshold dosages of bemegride or strychnine perfused at 2 and 0.2 mg/ml respectively were not changed by stress. Cold-water swim increased the number of cortical (but not cerebellar) [ 3H]flunitrazepam binding sites (+24%) but failed to alter cortical [ 3H]muscimol binding. This post-stress enhancement of binding sites, although suppressed by bicuculline (10 −4M) seems not to be dependent on GABAergic mechanisms. Indeed cold-water stress did not reduce the ability of muscimol (10 −6 and 10 5 M) and GABA (5 × 10 −6 and 5 × 10 −5 M) to increase flunitrazepam binding. Finally, this post-stress enhancement of benzodiazepine binding was not found to be paralleled by changes in the protective effects of diazepam against picrotoxin- or pentetrazol-induced seizures.