Chemically induced convulsive

In addition to locomotor activity, delta opioid agonists produce convulsions in mice [41,43], rats [34,35], and monkeys [44 46], In the past, chemical-induced convulsions induced by camphor or pentylenetetrazol (Metrazol) were used as treatments for depression today, however, ECT is the only convulsant therapy used because the treatment-induced effects are less unpleasant than those produced by chemical convulsants [47]. ECS was demonstrated to have antidepressant-like effects in the forced swim test in rats [3], and ECT is a very effective treatment for depression in humans. Based on these observations, it was proposed that delta opioid agonists produce antidepressant-like effects tough a convulsive- or electroconvulsive shock (ECS)-like mechanism of action [41]. 

All such animal procedures suffer from the obvious and basic problem that laboratory animals do not behave like humans and that humans cannot reliably interpret their reactions and behaviour. Thus we know that Parkinson s disease is caused by a degeneration of the dopaminergic nigrostriatal tract but its lesion in animals does not produce any condition which resembles human Parkinsonism, except in primates, even though there are functional tests (e.g. rotational movements) which readily establish that loss of dopamine function and also respond to its augmentation (Chapter 15). By contrast, there are many ways, e.g. electrical stimulation and the administration of certain chemicals, to induce convulsions in animals and a number of effective antiepileptic drugs have been introduced as a result of their ability to control such activity. Indeed there are some tests, as well as animals with varied spontaneous seizures, that are even predictive of particular forms of epilepsy. But then convulsions are a very basic form of activity common to most species and epileptic seizures that are characterised by behavioural rather than motor symptoms are more difficult to reproduce in animals. 

Bilobalide, a main constituent of the terpene fraction of the EGb, possesses anticonvulsant activity against convulsions induced by pentylenetetrazol, isoniazid, 4-0-methylpyridoxine, and electroshock. Reduced durations of convulsions and prolonged onset time of convulsions induced by chemical convulsants and electroshock were observed in mice treated orally with bilobalide (30 mg/kg/day, for 4 days). However, bilobalide has no protective effect against bicuculline- and strychnine-induced convulsions [99,100]. 

The sesquiterpenes caryophyllene oxide (36) and p-selinene (= p-eudesmene) (37) isolated from the hexane extract from leaves of Psidium guajava var. minor Mattos (Myrtaceae) potentiated pentobarbital sleep and increased the latency for PTZ-induced convulsions in mice blockade of extracellular Ca was observed in isolated guinea-pig ileum with the hexane extract and its fractions containing both sesquiterpenes (Meckes et al. 1997). The similarity between the chemical structures of the sesquiterpenes (34), (35), and (37) is noteworthy and could indicate relevant characteristic patterns required for central activity. 

Anticonvulsants - Many laboratories routinely screen new compounds for their ability to modify chemically and electrically induced convulsions. Annually a large niomber of compounds are reported to have anticonvulsant activity, and 1967 was no exception. Cited here are only selected examples - generally those which have shown promise in man. 

These are normally based on the use of either electrical stimulation or chemical convulsants. When applied generally, i.e. an electric shock to the whole brain or convulsants injected systemically, the resulting convulsions are indicative of generalised seizures. If they are applied locally to specific brain areas, the same approaches induce activity indicative of partial seizures. Also some animals can be bred in which seizures either occur spontaneously or can be induced easily by appropriate sensory stimulation. 

Toxicity is the ability of a substance/chemical to induce harmful/adverse effects on the organism. Adverse effects range from mild symptoms, such as headaches, to severe symptoms, like coma, convulsions, or death. Toxic chemicals trigger alterations of normal body functions, eventually leading to death of the organism. However, based on timely intervention and conditions of body... 

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