strychnine and Epilepsy

From binding studies using 3H-GABA and 3H-strychnine in dissected human brain material, inhibitory amino acid neurotransmitter receptors have a widespread distribution in the human CNS. Generally GABA receptors are predominant in the forebrain and upper brainstem whereas glycine receptors are more localized in the lower brainstem and spinal cord. Some areas (eg. the substantia nigra) have appreciable quantities of both receptors. Although glycine receptors are altered in some pathological conditions (eg. in Parkinson's disease, in the substantia nigra) the neuropharmacology of the glycine system is still poorly understood. On the other hand the GABA system has been intensively studied. Dysfunction of GABA receptors occurs in various neurological states, as epilepsy, Parkinson's disease and Huntington's chorea. Furthermore GABA agonists are active in animal models for dyskinesia, epilepsy and depression, amongst others. Clinical studies with progabide confirm these findings in animal models, and suggest that low-medium affinity GABA agonists are more appropriate clinical agents than are high or very high affinity GABA agonists. From these and many other findings there appears to be a very large potential for creating new pharmacological agents for different neuropsychiatric disorders based on agonist activity at inhibitory amino-acid receptors. From the example of progabide these compounds can be made not only specific for the receptor involved, but also to have a lower incidence of neurotoxic effects than presently available drugs.

Topics: Central Nervous System; Epilepsy; Humans; Huntington Disease; Mental Disorders; Nervous System Diseases; Neurotransmitter Agents; Parkinson Disease; Receptors, Cell Surface; Receptors, GABA-A; Receptors, Glycine; Seizures; Strychnine

Topics: Acoustic Stimulation; Adrenal Insufficiency; Age Factors; Animals; Body Constitution; Cats; Disease Susceptibility; Dogs; Epilepsy; Female; Genetic Variation; Humans; Hyperthyroidism; Mice; Neurotransmitter Agents; Pancreatic Diseases; Pregnancy; Seizures; Sex Factors; Strychnine

The paper is a review of the progress made over the past years in the understanding of electrical processes occurring during epileptic seizures as elicited by the local application of penicillin. The events at the cellular level of the neocortex are discussed, as well as cortico-subcortical relationships and microtopography of the seizure patterns. The increased excitability under penicillin induces a great number of feedback processes, the electrical effects of which become visible in the seizure EEG with its high degree of organization. Neocortical architectonics is of great importance for the shape of the potentials and their distribution. Seizure patterns of different shape are found in the different layers of the cortex.

Topics: Animals; Cell Membrane Permeability; Cerebral Cortex; Electrophysiology; Epilepsy; Evoked Potentials; Humans; Nerve Fibers; Penicillins; Pentylenetetrazole; Potassium; Snails; Strychnine

Recently, electrophysiological studies on sleep and wakefulness in birds have yielded useful results. Furthermore, recent evidence obtained in behavioral and electroencephalographical investigations of epileptic birds, induced neuropharmacologically or genetically, have led to recognition of the fact that epileptic seizures are present in aves, and that these seizures reveal many similarities between mammalian and avian epilepsy. While the investigation of birds is of obvrious value for demonstrating the neuropharmacological interrelationship with the brain, comparison of the correlation between abnormal behavior and the electroencephalogram in birds and higher vertebrates requires further research. In the present paper, normal and abnormal electroencephalographic activity associated with behavior of birds is reviewed. It was concluded that birds provide a useful preparation for studying experimental epilepsy.

Topics: Animals; Behavior, Animal; Bird Diseases; Birds; Brain; Chickens; Coturnix; Electric Stimulation; Electroencephalography; Epilepsy; Female; Male; Movement; Pentylenetetrazole; Poultry Diseases; Seizures; Sleep; Strychnine; Turkeys; Vocalization, Animal; Wakefulness

Topics: Action Potentials; Animals; Astacoidea; Cerebral Cortex; Electroencephalography; Epilepsy; Feedback; Freezing; Hippocampus; Membrane Potentials; Neurons; Penicillins; Strychnine; Synapses

Topics: Aminobutyrates; Animals; Choline; Epilepsy; Humans; Hydroxybutyrates; Hypertension; Hypoxia; Mental Disorders; Mice; Nervous System Diseases; Oxygen; Psychopharmacology; Seizures; Sound; Strychnine

Topics: Ammonia; Animals; Biochemical Phenomena; Biochemistry; Cell Membrane; Epilepsy; Fatty Acids; Humans; Methionine; Nervous System; Neurons; Picrotoxin; Potassium; Seizures; Sodium; Strychnine

Different parts of Malvaviscus arboreus Dill. Ex Cav. (M. arboreus) are traditionally used in the West Region of Cameroon to treat many diseases, including epilepsy.. To determine which part of M. arboreus offers the best anticonvulsant effect, and to assess the acute and sub-acute toxicity of the part of interest.. the anticonvulsant effect of the aqueous lyophilisate of the decoction of flowers, leaves, stems and roots of M. arboreus at various doses was evaluated and compared on the model of acute epileptic seizures induced by pentylenetetrazole (PTZ) (70 mg/kg), injected 1 h after oral administration of the various extracts. Out of these plant parts, the leaves were then selected to prepare the hydroethanolic extract and its anticonvulsant effect against PTZ at the doses of 122.5, 245 and 490 mg/kg, as well as its acute toxicity were compared with those of the aqueous lyophilisate of the leaves. The anticonvulsant effect of the aqueous lyophilisate of M. arboreus leaves was further evaluated on models of acute epileptic seizures induced by picrotoxin (PIC) (7.5 mg/kg), strychnine (STR) (2.5 mg/kg) and pilocarpine (350 mg/kg). The 28 days sub-acute toxicity, as well as the quantitative phytochemistry and the in vitro antioxidant potential (FRAP, DPPH, ABTS+) of the aqueous lyophilisate of the leaves of M. arboreus were also evaluated.. M. arboreus leaves showed the best anticonvulsant effect and the aqueous lyophilisate was the best extract. The latter significantly protected the animals against convulsions induced by PTZ (71.43%) (p < 0.01), PIC (57.14%) (p < 0.05) and STR (42%) and had no effect on pilocarpine-induced seizures. Furthermore, it showed no acute or sub-acute toxicity, and revealed a high content of flavonoids, saponins, tannins and alkaloids, and antioxidant activity in vitro.. The aqueous lyophilisate of the leaves of M. arboreus offers the best anticonvulsant effect on the extraction solvent used, and it would act mainly via a potentiation of the inhibitory systems of the brain (GABA, Glycine). In addition, its richness in bioactive compounds gives it an antioxidant potential, and it is not toxic in acute and sub-acute toxicity. All this justifies at least in part its empirical uses, and makes M. arboreus a candidate for the alternative treatment of epilepsy.

Topics: Anethum graveolens; Animals; Anticonvulsants; Antioxidants; Epilepsy; Pentylenetetrazole; Picrotoxin; Pilocarpine; Plant Extracts; Seizures; Strychnine; Water

Epilepsy is one of the most prevalent neurological illnesses defined by periodic seizures with or without loss of consciousness caused by aberrant neural activity. There are many allopathic medications available for the treatment of epilepsy such as phenytoin (PHY), but the side effects are a major concern. Therefore, the present study involved the evaluation of the pharmacological significance of. STR (3.5 mg/kg, i.p.) was injected into male rats 30 minutes after the pre-treatment of a standard drug (PHY: 20 mg/kg) and the two doses of EAV (EAV-200 and EAV-400 mg/kg, p.o.) to the respective groups to cause the convulsions. The anti-convulsant effect of EAV-200 and EAV-400 against STR-induced convulsion in rats was investigated in terms of convulsion onset, duration of convulsions, number of convulsions, and convulsion score. Furthermore, the mitochondrial function and integrity in the brain's prefrontal cortex (PFC) were also estimated.. EAV-400 significantly increased the onset of convulsion from 61.67 ± 3.051 to 119.2 ± 2.738 and reduced the STR-induced duration of convulsions from 144.8 ± 3.582 to 69.17 ± 3.736, number of convulsions from 4.000 ± 0.1592 to 1.533 ± 0.1542, and convulsion score from 5.000 ± 0.3651 to 2.833 ± 0.3073 in rats. EAV-400 significantly attenuated the STR-induced decrease in the mitochondrial function and integrity of the rat PFC. In rats, EAV-400 significantly accelerated the onset of convulsions while decreasing the STR-induced duration, frequency, and score.. Based on investigational findings, EAV-400 could be inferred to be a possible anti-epileptic option for the treatment of epilepsy of this plan in preclinical research.

Topics: Amaranthus; Animals; Anticonvulsants; Epilepsy; Male; Rats; Seizures; Strychnine

The decoction from the stem bark of Psychotria camptopus (Rubiaceae) is used in the Cameroonian pharmacopoeia to treat neurological pathologies including epilepsy.. The present work was undertaken to study the anticonvulsant properties of the aqueous (AE) and methanol (ME) extracts from the stem bark of P. camptopus in acute models of epileptic seizures in Wistar rats.. AE and ME were obtained by decoction and maceration of the stem bark powder in water and methanol, respectively. They were tested orally at the doses of 40, 80 and 120 mg/kg, on the latency of onset and duration of epileptic seizures induced by pentylene tetrazole (PTZ, 70 mg/kg, i.p.). The kinetic effect of both extracts at 120 mg/kg was evaluated. Their effects on diazepam (50 mg/kg) induced sleep and strychnine (STR, 2.5 mg/kg, i.p.) induced seizures were determined. ME was further tested on picrotoxin (PIC, 7.5 mg/kg, i.p.) and thiosemicarbazide (TSC, 50 mg/kg, i.p.) induced seizure models. The phytochemical composition of ME was assessed using LC-MS method, as well as its acute toxicity.. AE and ME significantly (p < 0.001) reduced the duration of seizures in both PTZ and STR models. Their maximal effect was observed at 1 h after administration, though their effect at 120 mg/kg was maintained (p < 0.05) up to 24 h post-treatment. Both extracts significantly (p < 0.01) reduced sleep duration. ME significantly (p < 0.001) increased the latency of rat death on PIC-induced convulsions. In TSC rats, ME significantly (p < 0.001) delayed the latency to the first convulsion, and decreased the duration and frequency of convulsions. ME showed no acute toxicity while its phytochemical screening revealed the presence of two flavonoids (Rutin and Butin), two triterpenoid saponins (Psycotrianoside B and Bauerenone) and four alkaloids (10-Hydroxy-antirhine, 10-hydroxy-iso-deppeaninol, Emetine and Hodkinsine). In conclusion, AE and ME from the stem bark of P. camptopus have comparable anticonvulsant properties. The effect of ME is likely due to the presence of flavonoids and alkaloid and the activation of GABA pathway. These results further justify and support the use of P. camptopus in traditional medicine for the treatment of epilepsy.

Topics: Animals; Anticonvulsants; Behavior, Animal; Diazepam; Disease Models, Animal; Epilepsy; Methanol; Mice; Pentylenetetrazole; Phytochemicals; Picrotoxin; Plant Bark; Plant Extracts; Plant Stems; Psychotria; Rats, Wistar; Seizures; Semicarbazides; Sleep; Sleep Latency; Strychnine; Water

An imbalance between inhibitory (GABA) and excitatory (Glutamate) neurotransmission contribute to the development of epilepsy. Earlier studies reported that dysregulation of GABA and glutamatergic activities resulted in status epilepticus (SE) and ultimately support the development of temporal lobe epilepsy (TLE), a type of resistant epilepsy. In the earlier work, 2-propanone-1,3,5,5-trimethyl-2-cyclohexen-1-ylidine demonstrated anticonvulsant activity against pentylenetetrazole (PTZ)-induced seizures. Apart from the PTZ-induced TLE, the dysregulation muscaranic receptors and glycine receptors are also widely reported phenomena in the development of temporal lobe epilepsy. Keeping the role of these two receptors in epilepsy, the present work investigated the effect of 2-propanone-1,3,5,5-trimethyl-2-cyclohexen-1-ylidine in pilocarpine-induced and strychnine-induced seizure models. Our results demonstrated that 2-propanone-1,3,5,5-trimethyl-2-cyclohexen-1-ylidine significantly delayed the onset of seizure with maximum protection from SE in pilocarpine-induced seizure model. However, the test compound did not revealed any effect on strychnine-induced seizures in mice. Based on these observations, we suggest that 2-propanone-1,3,5,5-trimethyl-2-cyclohexen-1-ylidine could be a potential candidate in reduction of SE and treatment of temporal lobe epilepsy (TLE) in future.

Topics: Animals; Anticonvulsants; Disease Models, Animal; Epilepsy; Male; Mice; Pentylenetetrazole; Pilocarpine; Seizures; Strychnine

The epileptogenic effects of applications of NMDA and kainic acid solutions to the frontal cortex were attenuated in rats receiving ketogenic diet (80% lipids, 3.3% carbohydrates, and 16.7% proteins) during 4 weeks. Spike latency increased, the power of focal epileptic activity decreased, and focus lifetime was shortened in these animals. Sodium benzylpenicillin and strychnine nitrate less markedly reduced epileptogenic activity.

Topics: Animals; Cerebral Cortex; Diet, Ketogenic; Epilepsy; In Vitro Techniques; Kainic Acid; Male; N-Methylaspartate; Penicillin G; Rats; Rats, Wistar; Strychnine

Acanthus montanus, Alchornea laxiflora, Hyptis spicigera, Microglossa pyrifolia, Piliostigma reticulatum, and Voacanga africana were evaluated with respect to anticonvulsant and sedative activity in mice using animal models (maximal electroshock (MES), N-methyl-D-aspartate (NMDA), pentylenetetrazol (PTZ), isonicotinic hydrazide acid (INH), picrotoxin (PIC), and strychnine (STR)-induced convulsions or turning behavior and diazepam-induced sleep). Acanthus montanus protected 66.6% of mice against MES-, PIC-, and STR-induced convulsions and 83.3% of mice from PTZ-induced convulsions. Alchornea laxiflora protected 75% and 87.5% of mice in the STR and NMDA tests, respectively, at a dose of 120 mg/kg. Hyptis spicigera protected 100 and 87.5% of mice against STR- and PTZ-induced convulsions, respectively, at a dose of 160 mg/kg. Microglossa pyrifolia protected 50% to 100% of mice against convulsions. Piliostigma reticulatum protected 62.5% to 100% of mice against convulsions and turning behavior. Voacanga africana protected 62.5% to 87.5% of mice against convulsions and turning behavior. All of the plants except A. laxiflora also exerted sedative activity by strongly increasing the total duration of sleep induced by diazepam.

Topics: Animals; Anticonvulsants; Convulsants; Diazepam; Dose-Response Relationship, Drug; Electroshock; Epilepsy; Excitatory Amino Acid Agonists; Hypnotics and Sedatives; Isoniazid; Male; Medicine, African Traditional; Mice; N-Methylaspartate; Pentylenetetrazole; Picrotoxin; Plants, Medicinal; Sleep Initiation and Maintenance Disorders; Stereotyped Behavior; Strychnine

To observe the anti-convulsion effect of Shenpu Decoction (SPD).. Experiments were conducted in three acute convulsion models (cardiazol seizure, strychnine convulsion and maximal electrical shock). Models were divided into the control group (A, treated by normal saline), the high, middle and low dose SPD groups (B, C and D, treated with SPD 9 g/kg, 6 g/kg and 4 g/kg respectively), and the nitrazepam treated group (E). The anti-convulsion effect of SPD was evaluated by 50% convulsion dose (CD50) detected in each group.. In cardiazol convulsion model, the CD50 detected in group A-E were 63.3 +/- 3.4 mg/kg, 116.2 +/- 3.4 mg/kg, 105.6 +/- 3.7 mg/kg, 74.0 +/- 3.7 mg/kg and 197.2 +/- 3.3 mg/kg respectively, while they were 0.71 +/- 0.04 mg/kg, 1.21 +/- 0.04 mg/kg, 1.19 +/- 0.04 mg/kg, 0.94 +/- 0.04 mg/kg and 1.16 +/- 0.04 mg/kg respectively in the strychnine convulsion model, and 67.1 +/- 2.6 V, > 140 V, 109.4 +/- 3.5 V, 84.4 +/- 3.1 V and 128.4 +/- 3.9 V in the maximal electrical shock model respectively.. SPD has a good anticonvulsion effect.

Topics: Animals; Anticonvulsants; Drugs, Chinese Herbal; Electric Stimulation; Epilepsy; Male; Mice; Pentylenetetrazole; Random Allocation; Strychnine

Topics: Adolescent; Beverages; Bipolar Disorder; Brain; Confusion; Diagnosis, Differential; Electrocardiography; Encephalitis, Viral; Epilepsy; Humans; Male; Muscle Rigidity; Phytotherapy; Poisoning; Strychnine; Tetanus; Tomography, X-Ray Computed

Anatomical connectivity is a prerequisite for cooperative interactions between cortical areas, but it has yet to be demonstrated that association fibre networks determine the macroscopical flow of activity in the cerebral cortex. To test this notion, we constructed a large-scale model of cortical areas whose interconnections were based on published anatomical data from tracing studies. Using this model we simulated the propagation of activity in response to activation of individual cortical areas and compared the resulting topographic activation patterns to electrophysiological observations on the global spread of epileptic activity following intracortical stimulation. Here we show that a neural network with connectivity derived from experimental data reproduces cortical propagation of activity significantly better than networks with different types of neighbourhood-based connectivity or random connections. Our results indicate that association fibres and their relative connection strengths are useful predictors of global topographic activation patterns in the cerebral cortex. This global structure-function relationship may open a door to explicit interpretation of cortical activation data in terms of underlying anatomical connectivity.

Topics: Animals; Brain Mapping; Cats; Cerebral Cortex; Computer Simulation; Convulsants; Epilepsy; Models, Neurological; Nerve Net; Neural Pathways; Strychnine

Recent analyses of association fibre networks in the primate cerebral cortex have revealed a small number of densely intra-connected and hierarchically organized structural systems. Corresponding analyses of data on functional connectivity are required to establish the significance of these structural systems. We therefore built up a relational database by systematically collating published data on the spread of activity after strychnine-induced disinhibition in the macaque cerebral cortex in vivo. After mapping these data to two different parcellation schemes, we used three independent methods of analysis which demonstrate that the cortical network of functional interactions is not homogeneous, but shows a clear segregation into functional assemblies of mutually interacting areas. The assemblies suggest a principal division of the cortex into visual, somatomotor and orbito-temporo-insular systems, while motor and somatosensory areas are inseparably interrelated. These results are largely compatible with corresponding analyses of structural data of mammalian cerebral cortex, and deliver the first functional evidence for 'small-world' architecture of primate cerebral cortex.

Topics: Animals; Brain Mapping; Cerebral Cortex; Cluster Analysis; Convulsants; Epilepsy; Models, Neurological; Neural Pathways; Primates; Strychnine

Alongside GABA, glycine is the major inhibitory transmitter in the central nervous system. Application of the glycine receptor blocker strychnine is known to evoke epileptiform phenomena. The present paper addresses the question whether postsynaptic calcium currents through L-type channels contribute to strychnine-induced epileptiform field potentials (EFP). To test for this, the antiepileptic effect of the specific L-type calcium channel blocker, verapamil, in hippocampal and neocortical slices was investigated. In parallel with this, the antiepileptic efficacy of the unspecific calcium channel modulator, flunarizine, was tested with respect to pharmacotherapy of epilepsies. In both preparations, the L-type calcium channel blocker, verapamil, was able to suppress EFP. In neocortical slices, EFP were blocked in all experiments, whereas in hippocampal slices, in 3 out of 11 experiments, no complete suppression occurred. Flunarizine acted in a similar way. It is concluded that L-type calcium channels are involved in strychnine-induced epilepsy, but to a greater extent in the neocortex than in the hippocampus.

Topics: Animals; Calcium Channel Blockers; Calcium Channels; Calcium Channels, L-Type; Epilepsy; Evoked Potentials; Female; Flunarizine; Guinea Pigs; Hippocampus; In Vitro Techniques; Male; Neocortex; Strychnine; Verapamil

Topics: Amygdala; Animals; Electroencephalography; Epilepsy; Macaca; Penicillins; Strychnine; Thalamus

Topics: Amygdala; Analysis of Variance; Animals; Epilepsy; Kindling, Neurologic; Kynurenic Acid; Male; Rats; Rats, Sprague-Dawley; Receptors, Glycine; Receptors, Neurotransmitter; Strychnine

Seizures elicited by posture change and intraperitoneal administration of convulsants were studied ontogenetically in the Mongolian gerbil (Meriones unguiculatus). In posture change, the first signs of seizure appeared after age 6 weeks with maximal frequency at 8-9 weeks. Adults developed complex, but stereotyped, seizures. Facial twitch was followed by the generalized convulsion, further progressing to trembling of the limbs and then kicking of the hindlimb (full seizure) after 55 days of age. Pentylenetetrazole induced a seizure similar to the full event in gerbils as young as 37 days of age. The seizure pattern elicited by strychnine or glutamate was different from that of pentylenetetrazole.

Topics: Animals; Behavior, Animal; Brain; Electroencephalography; Epilepsy; Gerbillinae; Neurotransmitter Agents; Pentylenetetrazole; Posture; Receptors, GABA-A; Seizures; Strychnine

Intracellular responses of neurons of the suprasylvian gyrus to the intracortical stimulation (ICS) before and after superficial application of strychnine were investigated in experiments on immobilized and unanaesthetized cats. The normal cortex neurons reacted to ICS by monosynaptic EPSPs followed by IPSPs. Strychnine application triggered the epileptiform activity and appearance in neurons of paroxysmal depolarization shifts of the membrane potential (MP) which were replaced by hyperpolarization potentials. An increase and summation of the latter elicited the MP enlargement and either reduction or suppression of background spike activity. Intracellular injections of EGTA blocking the membrane calcium-dependent potassium conductivity (gK(Ca)) have eliminated the hyperpolarization potentials. Development of epileptiform activity was accompanied by depression of IPSPs and increase of the monosynaptic EPSPs. The contribution of gK(Ca) and of postsynaptic inhibition to the epileptogenesis is discussed.

Topics: Animals; Cats; Cerebral Cortex; Egtazic Acid; Epilepsy; Evoked Potentials; Membrane Potentials; Neurons; Potassium Channels; Restraint, Physical; Strychnine

In experiments on freely moving male Wistar rats it was shown that IOS-1.1212 (1,4-dihydropyridine) in a dose 2 and 10 mg/kg (i. p.) suppressed the penicillin-induced focal epileptic activity in cerebral cortex. Similar suppressing effect of IOS-1.1212 was shown on acute generalized tonic-clonic pentylenetetrazol (PTZ) seizures (75 mg/kg i. p.) and on chronic PTZ administration (PTZ-kindling, 30 mg/kg i. p. during 30 days): when injected 30 min before each PTZ administration it delayed the development of kindling-induced seizures susceptibility in randomized animals (series 1) and attenuated the severity of seizures in PTZ-sensitive animals (series 2). However, IOS-1.1212 had no effect on the strychnine-induced focal epileptic activity. In male Icr:Icl mice IOS-1.1212 in a dose 1.5 and 5 mg/kg also influenced the PTZ convulsions (i. v. titration of 1% solution at a rate of 0.01 ml/s) and had no effect on the strychnine convulsions (i. v. titration of 0.01% solution at a rate of 0.01 ml/s) and on maximal electroshock. In addition, IOS-1.1212 significantly increased antiepileptic effect of phenobarbital on maximal electroshock.

Topics: Animals; Anticonvulsants; Calcium Channel Blockers; Dihydropyridines; Epilepsy; Male; Penicillins; Pentylenetetrazole; Rats; Rats, Inbred Strains; Strychnine

Reactions of cortical suprasylvian gyrus neurons were investigated intracellularly after supracortical strychnine application in immobilized and anaesthetized cats. It was shown that paroxysmal depolarizing shifts of membrane potential could be accompanied by de- and hyperpolarizing afterpotentials. When passing from epileptiform to normal physiological activity, short afterhyperpolarizations, 300-500 ms in duration, were converted into inhibitory postsynaptic potentials which were also accompanied by a decrease in membrane potential. When the frequency of paroxysmal discharge was less than 1 s, prolonged (1-2 s) afterhyperpolarizations were observed; at a higher frequency their summation led to tonic hyperpolarization of the membrane. The ictal discharges were accompanied by postictal hyperpolarizations of up to 30 s duration. The intracellular injection of EGTA blocking Ca2(+)-dependent potassium conductivity eliminated prolonged after- and postictal hyperpolarizations and produced depolarizing afterpotentials and a gradual depolarization of cell membranes. Our results indicate that the development of short hyperpolarizing afterpotentials could be determined by the inhibitory synaptic effects. The activation of Ca2(+)-dependent potassium conductivity caused by the development of prolonged afterhyperpolarizations and postictal polarizations, as well as maintained tonic hyperpolarization of cell membranes. Obviously, the depolarizing afterpotentials are of a non-synaptic origin and can be induced by inward calcium current.

Topics: Animals; Calcium; Cats; Cerebral Cortex; Egtazic Acid; Electric Conductivity; Electric Stimulation; Electrophysiology; Epilepsy; Membrane Potentials; Neurons; Potassium; Strychnine

Intracellular responses of neurons of cortical strychninized suprasylvian gyrus were investigated in experiments on immobilized and unanaesthetized cats. Paroxysmal depolarizing shifts (PDS) of the neuronal membrane potential were registered. They consisted of the burst discharge (BD) and slow depolarization wave. By means of intracellular stimulation it was shown that PDS could be summarized and were able to change their form and size. BD in PDS were triggered by large EPSPs which could be elicited from paroxysmal responses. Presumably, the intradendritic recordings have shown the presence of large EPSPs during generation of epileptiform discharges in the neocortex. In some neurons PDSs were accompanied by hyperpolarizing potentials which were apparently IPSPs because they were reversed at the intracellular Cl- injections. The contribution of excitatory and inhibitory synaptic influences to the neuronal paroxysmal responses is discussed.

Topics: Animals; Cats; Cerebral Cortex; Electric Stimulation; Electrodes, Implanted; Epilepsy; Evoked Potentials; Membrane Potentials; Neural Inhibition; Neurons; Receptors, Neurotransmitter; Strychnine

Reactions of isolated cortical slab neurons to the supracortical application of strychnine were investigated with intracellular registration in experiments on unanaesthetized and immobilized cats. It was shown that some neurons demonstrated prolonged depolarizing potentials (PDP) spontaneously and as reactions to single intracortical electrical stimuli. The development of these potentials could be a result of transformation of the reaction of the "paroxysmal depolarizing shift (PDS)--hyperpolarization" type, where hyperpolarizations were replaced by depolarizing potentials. A gradual increase of depolarizing afterpotentials resulted in DDP generation. These transformations, as a rule, were accompanied by amplification of the summary epileptiform activity in an isolated cortical slab. The suggestion was made that the DDP generation was determined by an increase in the Ca(++)-conductance of the neuronal membrane in an isolated cortical slab with the intensification of paroxysmal reactions.

Topics: Animals; Cats; Cerebral Cortex; Electric Stimulation; Epilepsy; In Vitro Techniques; Membrane Potentials; Microelectrodes; Neurons; Strychnine

Reactions of neuronal and glial cells of an isolated cortical slab to direct electrical stimulation after supracortical strychnine application were investigated in experiments on immobilized and unanaesthetized cats. Strychnine evoked single epileptiform discharges and afterdischarges in the isolated cortical slab and large paroxysmal depolarization shifts (PDS) of the membrane potential (MP) in the neurons. It was shown that spontaneous summary epileptiform discharges and cellular activity of neurons investigated were synchronized slightly. Electrical stimuli produced a generalized paroxysmal activity in the isolated slab. Neuronal PDSs were accompanied by refractory periods which development did not depend on the MP level. Strychnine enhanced a number of neurons with the background activity in which PDS were generated by rhythmic depolarizing MP oscillations of the nonsynaptic origin. It was shown also that epileptiform reactions of the strychninized isolated cortical slab to the single stimuli were accompanied by large depolarization shifts of the glial cells' MP. The suggestion is made that the paroxysmal excitation development in the strychninized isolated cortical slab was determined by non-synaptic factors and was strongly related to the changes of the extracellular potassium concentration.

Topics: Action Potentials; Animals; Cats; Cerebral Cortex; Epilepsy; In Vitro Techniques; Neuroglia; Neurons; Reaction Time; Strychnine

Topics: Animal Welfare; Animals; Animals, Laboratory; Epilepsy; Humans; Strychnine

Simultaneous recordings from three laminae within the cat visual cortex following differential intralaminar injections of strychnine (i) confirmed that low strychnine concentrations (5 mM) induce interictal-like epileptiform abnormalities (late responses) only when injected into superficial layers 2 and 3, (ii) revealed that these abnormalities are generated locally within these layers, and (iii) showed that they remain local phenomena by not spreading vertically into other cortical layers. Higher strychnine concentrations (20 mM), however, (iv) obscured these laminar differences by increasing layer 4 sensitivity to this agent in addition to the maximally sensitive superficial layers, and further (v) revealed nonlocal, vertically propagating, interictal-like abnormalities (late responses) following layer 4 injections which are preceded by an increase in thalamocortically mediated activity within this layer (enhanced physiologic responses). When penicillin was used as the convulsant, propagated interictal-like responses (late responses) induced in any layer were always preceded by a thalamocortically mediated response from layer 4 (enhanced physiologic responses); a condition clearly unlike the 5 mM but similar to the 20 mM strychnine foci observed in this study. These results suggest that convulsant action upon the thalamocortical circuitry of layer 4 is essential for the development of propagating as opposed to local epileptiform activity. Further, these results may also help explain why some cortical seizure disorders remain localized (focal) whereas others secondarily generalize to distal brain sites (i.e., complex partial seizures of extratemporal origin).

Topics: Animals; Cats; Cerebral Cortex; Electrophysiology; Epilepsy; Penicillins; Strychnine; Thalamus

In free behaviour experiments on rats it has been shown that the intraperitoneal injection of delta sleep-inducing peptide (DSIP) (100 micrograms/kg) suppressed penicillin-induced relatively moderate epileptic foci which generated spike potentials as well as severe foci with ictal epileptic discharges. In the experiments on cats it was shown that intravenous DSIP injection (100 micrograms/kg) suppressed strychnine-induced epileptic focus and complexes of epileptic foci.

Topics: Animals; Cats; Cerebral Cortex; Delta Sleep-Inducing Peptide; Epilepsy; Male; Penicillins; Rats; Strychnine

Influence of cerebral hypoxia and hyperventilatory hypocapnia on the ECoG and focal epileptiform activity of the cerebral cortex induced with local application of strychnine was studied in cats with transection of spinal cord at C1. Although both hypoxia and hypocapnia produced synchronization of the cerebral cortex electrical activity, i.e. exerted the same effects on the ECoG, their influence on cortical excitability was quite different: hypoxia suppressed the epileptiform activity whereas hypocapnia facilitated it.

Topics: Animals; Carbon Dioxide; Cats; Cerebral Cortex; Decerebrate State; Electroencephalography; Epilepsy; Hypoxia, Brain; Strychnine

Experiments on mollusk neurons showed the presence of 3 types of neurons with different activity character and different sensitivity to convulsants. The highest sensitivity to corazol and other convulsants was characteristic of spontaneuosly active "impulse" motoneurons with the threshold dose of corazol being 1 X 10(-4) M. Intergrative neurons without background spontaneous activity were the least sensitive, with the threshold dose of corazol being 1-5 X 10(-3) M. "Impulse" cells of the mollusk were compared with epileptic neurons of the brain. It was shown that "impulse" and epileptic activity was brought about by a peculiar change in the ionic permeability of the membrane, activation of the channels of a slow ascending current, a slow growth of potassium permeability and the resultant appearance of an area of negative resistance in the volt-ampere characteristics of ionic currents of the membrane. The convulsants were capable of inducing these changes in the electrophysiological characteristics of the neuronal membrane, while classical anticonvulsants eliminated them.

Topics: Animals; Anticonvulsants; Camphor; Cell Membrane Permeability; Cobalt; Convulsants; Electric Conductivity; Epilepsy; Ganglia; Helix, Snails; In Vitro Techniques; Models, Neurological; Pentylenetetrazole; Strychnine

Transient foci of epileptiform alteration in neuronal population activity were induced by microinjection of strychnine sulfate into different layers of cat striate cortex. Potentials evoked by visual field-specific photic stimulation were recorded from microelectrodes at the injection site and in adjacent laminae. Epileptogenesis, characterized by an enhancement of the normal primary response followed by the development of a large late potential, occurred only with strychnine injections into superficial pyramidal layers 2 and 3. By contrast, stellate layer 4 has been shown to be most susceptible to epileptogenic effects of penicillin and bicuculline. Since disinhibitory convulsants should be most effective where their actions antagonize the prevalent type of inhibition, these findings suggest that there may be a laminar segregation of neocortical inhibition, possibly glycine-mediated in layers 2-3 and probably gamma aminobutyric acid (GABA)-mediated in layer 4.

Topics: Animals; Cats; Epilepsy; Evoked Potentials, Visual; Neural Inhibition; Penicillins; Photic Stimulation; Reaction Time; Strychnine; Visual Cortex

Topics: Animals; Diazepam; Epilepsy; Male; Rats; Strychnine

Allylglycine increased the concentration of pyridoxal phosphate in cerebral cortex from 1011.4 +/- 25.0 to 1318.0 +/- 66.3 and decreased it in cerebellum from 1289.0 +/- 49 to 1147.7 +/- 119.4 ng/g wet tissue during the preictal period. Mercaptopropionic acid increased the concentration of pyridoxal phosphate in cerebellum from 1525 +/- 91 to 1985.7 +/- 275 ng/g wet tissue. Similar effects were noted in hippocampus and cerebral cortex. Picrotoxin increased the concentration of pyridoxal phosphate in hippocampus from 938.7 +/- 44 to 1043 +/- 118 but decreased it in cerebral cortex from 1124.52 +/- 124 to 979.4 +/- 15 ng/g wet brain. The effects of strychnine were identical to those of allylglycine. Bicuculline reduced the concentration of pyridoxal phosphate in cerebral cortex from 1184 +/- 61 to 1075.14 +/- 78 ng/g wet brain.

Topics: 3-Mercaptopropionic Acid; Allylglycine; Animals; Bicuculline; Brain; Convulsants; Epilepsy; Male; Picrotoxin; Pyridoxal Kinase; Pyridoxal Phosphate; Rats; Rats, Inbred Strains; Strychnine

Topics: Animals; Autonomic Nervous System; Biological Evolution; Brain; Electrophysiology; Epilepsy; Humans; Interneurons; Motor Neurons; Nerve Tissue Proteins; Neuroglia; Physical Stimulation; Proprioception; Reflex, Abnormal; RNA; Seizures; Strychnine

Topics: Animals; Anticonvulsants; Cats; Cerebral Cortex; Cobalt; Disease Models, Animal; Electroencephalography; Epilepsy; Estrogens, Conjugated (USP); Evaluation Studies as Topic; Penicillin G; Strychnine; Taurine

Topics: Action Potentials; Animals; Chlorides; Electric Stimulation; Epilepsy; Guinea Pigs; Hippocampus; Strychnine; Synaptic Transmission; Thiosemicarbazones

Topics: Action Potentials; Animals; Brain; Cats; Cell Membrane Permeability; Cold Temperature; Cortical Spreading Depression; Disease Models, Animal; Electric Stimulation; Electroencephalography; Electrophysiology; Epilepsy; Membrane Potentials; Metabolic Diseases; Models, Biological; Neurons; Neurons, Afferent; Neurophysiology; Ouabain; Penicillins; Pentylenetetrazole; Potassium; Receptors, Neurotransmitter; Sodium; Strychnine; Synaptic Membranes; Synaptic Vesicles

Topics: Electric Stimulation; Electroencephalography; Epilepsy; Evoked Potentials; Motor Cortex; Strychnine; Thalamus

Topics: Anesthetics, Local; Animals; Blood-Brain Barrier; Central Nervous System Stimulants; Cerebral Cortex; Cerebral Decortication; Dioxins; Electroencephalography; Epilepsy; Lidocaine; Methods; Neurosurgery; Penicillin G; Rabbits; Strychnine

Topics: Animals; Cats; Cerebral Cortex; Corpus Callosum; Diencephalon; Electroencephalography; Epilepsy; Female; Hippocampus; Hypothalamus; Male; Mesencephalon; Neural Pathways; Penicillins; Reticular Formation; Strychnine; Thalamic Nuclei

Topics: Aluminum; Animals; Animals, Newborn; Cats; Electric Stimulation; Electroencephalography; Epilepsy; Seizures; Strychnine

Topics: Animals; Cats; Electric Stimulation; Electroencephalography; Epilepsy; Evoked Potentials; Pyramidal Tracts; Strychnine; Synapses

Topics: Animals; Cats; Cerebral Cortex; Epilepsy; Evoked Potentials; Light; Mescaline; Noise; Strychnine

Topics: Animals; Cats; Cerebral Cortex; Electroencephalography; Epilepsy; Strychnine

Topics: Alanine; Aminobutyrates; Animals; Cats; Electroencephalography; Epilepsy; Penicillins; Strychnine

Topics: Animals; Cats; Electroencephalography; Epilepsy; Pentylenetetrazole; Strychnine

Topics: Cats; Electrodes; Electroencephalography; Epilepsy; Research; Seizures; Somatosensory Cortex; Strychnine; Toxicology

Topics: Activation Analysis; Animals; Cerebral Cortex; Dogs; Electroencephalography; Epilepsy; Hypothermia, Induced; Ice; Injections, Intravenous; Pentylenetetrazole; Strychnine; Thermography; Thermometers

Topics: Anticonvulsants; Arisaema; Caffeine; Electric Injuries; Epilepsy; Mice; Pentylenetetrazole; Pharmacology; Plants, Medicinal; Research; Seizures; Strychnine

Topics: Amygdala; Animals; Cats; Cerebral Cortex; Electroencephalography; Electromyography; Epilepsy; Eye Movements; Hippocampus; Limbic System; Seizures; Sleep; Strychnine

Topics: Acetylcholine; Animals; Cerebral Cortex; Electroencephalography; Epilepsy; Haplorhini; Research; Seizures; Strychnine

Topics: Benzodiazepines; Chlordiazepoxide; Diazepam; Epilepsy; Pharmacology; Rabbits; Research; Strychnine; Tranquilizing Agents

Topics: Animals; Cerebral Cortex; Dogs; Epilepsy; Humans; Strychnine

Topics: Cerebral Cortex; Epilepsy; Epinephrine; Strychnine

Topics: Animals; Convulsants; Epilepsy; Haplorhini; Picrotoxin; Strychnine; Sulfates

Topics: Epilepsy; Epinephrine; Seizures; Strychnine

Topics: Cerebral Cortex; Epilepsy; Humans; Strychnine

Topics: Electricity; Epilepsy; Humans; Seizures; Strychnine; Vestibule, Labyrinth

Topics: Electroencephalography; Epilepsy; Epilepsy, Temporal Lobe; Hippocampus; Humans; Strychnine

Topics: Electric Stimulation; Epilepsy; Extrapyramidal Tracts; Humans; Pyramidal Tracts; Seizures; Strychnine

Topics: Anticonvulsants; Epilepsy; Humans; Infusions, Intravenous; Pentylenetetrazole; Seizures; Strychnine