Anticonvulsant Effects Of Diazepam Research Articles

Cu2+ is the active principle of an endogenous substance from porcine cerebral cortex which antagonizes the anticonvulsant effect of diazepam.

A boiled extract of porcine cerebral cortex was fractionated on Sephadex G-75 and LH-20 followed by paper chromatography of the active fraction having inhibitory activity towards [3H]GABA binding to rat brain synaptic membranes. A ninhydrin-negative substance migrating more quickly than authentic GABA was identified as a copper-GABA complex. The complex inhibited specific [3H]GABA binding (IC50 approximately equal to 1 microM) and antagonized the anticonvulsant effect exerted by intraamygdaloid injection of diazepam. The effect of a synthetic copper-GABA complex was compared and found to be similar to the endogenous complex. Cu2+ alone has no affinity for the GABA recognition site but antagonizes the anticonvulsant effect of diazepam. Therefore, Cu2+ is suggested to be the pharmacologically active principle of the endogenous substance. Cu2+ does not seem to function via the recognition site of the GABA receptor.

Modification of the anticonvulsant efficacy of diazepam by Ro-15-1788 in the kindled amygdaloid seizure model

The effects of various doses of diazepam and the new central benzodiazepine antagonist Ro-15-1788 were investigated in fully amygdaloid kindled rats. Diazepam had a pronounced dose-dependent anticonvulsant effect in this model. Ro-15-1788 dose-dependently reduced the behavioral ranks of the elicited kindled seizures to a maximum of 60% of control without consistently modifying the afterdischarge duration. No prestimulation convulsant effects were seen with Ro-15-1788. When 2 mg/kg i.p. of Ro-15-1788 was given after various doses of diazepam, the prestimulation sedation and ataxia caused by the high dose of diazepam (2 mg/kg i.p.) was reversed. The anticonvulsant effects of diazepam (0.5–2.0 mg/kg) were attenuated by treatment with 2 mg/kg Ro-15-1788. At the low dose of diazepam (0.25 mg/kg), increased reduction of behavioral rank and afterdischarge duration was seen after the 2 mg/kg dose of Ro-15-1788. Thus, Ro-15-1788 appears not to have proconvulsant properties in the kindled amygdaloid seizure model. Further, Ro-15-1788 appears to have some anticonvulsant properties of its own. Mixed agonist and antagonist effects were seen with Ro-15-1788 when given after various doses of diazepam in this model.

The anticonvulsant effects of diazepam and phenobarbital in prek1ndled and kindled cortical seizures

The effects of various doses of diazepam (0.5–4 mg/kg) and phenobarbital (15–60 mg/kg) were determined on prekindled (focal) and kindled (generalized) cortical seizures in the same rats. Only high sedating doses of diazepam or phenobarbital reduced the elicited afterdischarge duration (ADD) and behavioral response in the prekindled focal cortical seizure. Against the kindled seizure, both diazepam and phenobarbital showed a marked and statistically significant increase in effectiveness in all but the smallest doses tested. The ADD of the kindled cortical seizures was reduced to prekindled lengths by diazepam (1–4 mg/kg) or phenobarbital (30–60 mg/kg). The increased anticonvulsant effectiveness found in this study is similar to previous findings with diazepam and phenobarbital against prekindled and kindled amygdaloid seizures, but stands in contrast to findings with prekindled and kindled pentylenetetrazol seizures.

The anticonvulsant effects of diazepam and phenobarbital in prekindled and kindled seizures in rats

The effects of various doses of diazepam (0.5–4 mg/kg) and phenobarbital (7.5–60 mg/kg) were determined on prekindled and kindled amygdaloid seizures in the same rats. Diazepam was ineffective against the prekindled focal seizures, but demonstrated profound and statistically significant control of the kindled seizures. In the kindled state, diazepam reduced the afterdischarge duration and seizure rank score to prekindled levels. Only the largest sedating dose of phenobarbital produced a reduction of both prekindled afterdischarge duration and seizure rank score. Against the kindled seizure, phenobarbital showed a marked and statistically significant increase in effectiveness in all but the smallest dose tested. The afterdischarge duration of kindled seizures was reduced to prekindled levels by 15–60 mg/kg of phenobarbital, while seizure rank score was reduced to prekindled levels by 30 and 60 mg/kg phenobarbital. The effects of two doses of diazepam (0.5 and 2.5 mg/kg) and phenobarbital (7.5 and 30 mg/kg) were tested against prekindled and kindled pentylenetetrazol (PTZ)-induced seizures. Preliminary work with 3 doses of pentylenetetrazol (30, 40 and 60 mg/kg) demonstrated that repeated doses of 30 mg/kg readily kindled seizures without the significant mortality seen with larger doses. Both diazepam and phenobarbital were less effective against seizures kindled with 30 mg/kg pentylenetetrazol compared to prekindled seizures. The comparative lack of effect that was seen with diazepam and phenobarbital against the pentylenetetrazol kindled seizure at doses associated with control of the kindled amygdaloid seizure may reflect an underlying difference in the pathogenesis of kindling between these seizure models. Further, the lack of suppression of the prekindled amygdaloid afterdischarge duration by large doses of diazepam, in contrast to large doses of phenobarbital, may also reflect differences between the mechanisms of action of these two drugs. This paradigm provides a model for testing the effectiveness of anticonvulsants during the progressive development of various epileptogenic seizures.

Correlation between benzodiazepine receptor occupation and anticonvulsant effects of diazepam

The benzodiazepines are potent anticonvulsants for a wide variety of experimental and clinical seizure disorders. The demonstration of saturable, high-affinity and stereospecific binding sites for the benzodiazepines in the mammalian central nervous system suggests the presence of pharmacological receptors mediating the anticonvulsant properties of these compounds. The good correlation between the anticonvulsant potencies of a series of benzodiazepines and their ability to inhibit 3H-diazepam binding in vitro further supports this hypothesis, but evidence for a direct interaction between benzodiazepines and their receptors, and a subsequent inhibition of seizure activity (or elevation of seizure threshold) is lacking. Recent reports from our laboratory and others have demonstrated the feasibility of labelling benzodiazepine receptors in vivo following parental administration of tritiated benzodiazepine. This technique permits one to study the relationship between the anticonvulsant activity of the benzodiazepines in vivo and the number of 'drug-occupied' receptors in vitro. We now report that there is an excellent correlation between benzodiazepine receptor occupancy by diazepam and protection against pentylenetetrazol-induced seizures. Furthermore, these results demonstrate that only a small fraction of benzodiazepine receptors need be occupied to produce a complete anticonvulsant effect.

Further studies on the site of action of diazepam: Anticonvulsant effect in the rabbit

The site of the anticonvulsant action of diazepam was studied by means of direct intracerebral chemostimulation in conscious rabbits with chronically implanted cannulae and recording electrodes. In order to evaluate anticonvulsant effectiveness, two procedures were used: (a) elevation in pentylenetetrazol (PTZ) threshold for appearance of spike activity in the EEG record; (b) elevation in the threshold of limbic after-discharges. Diazepam was injected in one of three regions: anterior amygdaloid nucleus (AA), basal amygdaloid nucleus (AB), and dorsal hippocampus (DH). Application of diazepam in the AA strongly elevated the PTZ threshold in a reversible and doserelated manner; injections in the AB or DH were ineffective. Phenobarbital was also ineffective in all regions investigated. The threshold of amygdalo-hippocampal after-discharges was elevated after application of diazepam in the AA, but not after injection in the DH. Hippocampal-amygdaloid after-discharges were not influenced by the drug from either the AA or DH. It is concluded that the amygdaloid nucleus, and particularly its anterior part, plays a crucial role in the anticonvulsant effect of diazepam in the rabbit.