GABA exhibits depolarizing action in the immature neurons due to high intracellular activity of chloride ions. It is maintained by cation-chloride cotransporter NKCC1 which is present in immature brain. Bumetanide is a specific inhibitor of this cotransporter. We studied possible anticonvulsant activity of bumetanide in pentyl enetetrazol-induced seizures in three age groups of rat pups (7, 12, and 18 days old). Pretreatment with bumetanide (0.2-1 mg/kg i.p.) resulted in dose-dependent decrease of incidence of the tonic phase of generalized tonic-clonic seizures in 12-day-old rats only. No effect was observed in younger and older animals. Higher dose of bumetanide (2.5 mg/kg) did not affect tonic convulsions but, on the contrary, decreased latencies of generalized seizures in 12-day-old animals. Lack of marked anticonvulsant effect is probably due to relative maturity of neurons in the brainstem where the generator of generalized seizures is localized. Age- and dose-specific suppression of the tonic phase needs further analysis. and Obsahuje seznam literatury
Neuroactive steroids represent potential antiepileptic drugs. We tested a newly synthesized analogue of allopregnanolone 3α- hydroxy-21ξ,22-oxido-21-homo-5α-pregnan-20-on (HOHP) against two types of pentylenetetrazol-induced seizures (100 mg/kg s.c.) in 12- and 25-day-old rats. Ganaxolone, a neuroactive steroid in clinical trials, served as a reference drug. Pretreatment with either steroid suppressed generalized tonicclonic seizures in both age groups, their efficacy was comparable. HOHP as well as ganaxolone were more active in 12- than in 25-day-old rats (effective doses were 40 and 60 mg/kg, respectively). Minimal clonic seizures, which can be elicited only in 25-day-old rats, were not influenced by any drug. Very short duration of anticonvulsant action of HPOP demonstrated in 12-day-old animals indicates that this drug might be used only in acute treatment in epileptology., P. Mareš, H. Kubová, A. Kasal., and Obsahuje bibliografii a bibliografické odkazy
The action of progabide against motor seizures elicited by pentylenetetrazol was studied in 7-, 12-, 18-, 25-day-old and adult rats. Progabide (dissolved in dimethylsulfoxide) was injected in doses from 12.5 to 150 mg/kg i.p. 30 min before pentylenetetrazol. Minimal seizures were not affected by solvent or progabide pretreatment. The action of progabide against major, i.e. generalized tonic-clonic seizures, changed with age: adult rats exhibited a tendency to suppression of whole major seizures, whereas specific suppression of the tonic phase was observed in rat pups during the first three weeks of life. The only effect seen in 25-day-old animals was prolongation of the latency of major seizures after the highest dose of progabide.
The anticonvulsant action of SL 75 102, a metabolite of Progabide, was studied in a model of pentylenetetrazol- induced motor seizures in adult and 12-day-old rats. SL 75 102 suppressed generalized tonic-clonic seizures in adult rats and restricted the tonic phase of these seizures in rat pups. SL 75 102 was less effective than Progabide. In addition, some minor differences in anticonvulsant actions of these two drugs were observed.
The action of two potential anticonvulsants, CM 40907 (10-50 mg/kg i.p.) and SR 41378 (1.25-20 mg/kg i.p.) against metrazol-induced seizures was studied in rats 7, 12, 18 and 25 days old. Two types of motor seizures - minimal, clonic and major, generalized tonic-clonic - were elicited by a 100-mg/kg dose of metrazol (s.c.) and their incidence and latency were evaluated. The severity of seizures was expressed as a score on a 5-point scale. Dimethylsulfoxide, an organic solvent, exhibited anticonvulsant action only in doses far exceeding those used for dissolving the two anticonvulsants. Both drugs suppressed minimal as well as major seizures in all age groups studied in a dose-dependent manner, SR 41378 being approximately four times more potent than CM 40907. The latencies could be measured only in animals given low doses of anticonvulsants. CM 40907 did not change the latencies whereas SR 41378 prolonged them. The severity of seizures was decreased again in a dose-dependent manner. There were only minor changes in the efficacy of CM 40907 among the four age groups. On the contrary, SR 41378 exhibited an extreme efficacy in 7-day-old rat pups, where even the 1.25 mg/kg dose signifcantly decreased the incidence and severity of seizures. The efficacy in the remaining three age groups was approximately at the same level as in adult rats.
Two doses of alprazolam (0.1 and 0.5 mg.kg“1) were tested against a model of human absences - rhythmic EEG activity elicited by low doses of pentylenetetrazol (35 mg.kg-1) - in 10 unrestrained rats with implanted cortical electrodes. Alprazolam delayed the onset of epileptic EEG activity, decreased the number of rhythmic episodes and shortened the total duration of rhythmic activity in a dose-dependent manner. The average duration of episodes of rhythmic activity remained unchanged; other benzodiazepines studied previously were able to influence this measure.
Effect of phénobarbital (PhB, 20 and/or 40 mg/kg) on epileptic ECoG phenomena induced by metrazol was studied in acute experiments in rats aged 7, 12, 18, 25 and 90 days. Fractionated administration of metrazol (20 mg/kg i.p. each 300 s) was used to quantify the effects of PhB. First signs of metrazol action (sharp elements and/or rhythmic metrazol activity) were not reliably influenced by PhB. On the contrary, the latency of the first EEG seizures as well as of the first generalized EEG seizures was prolonged and thus a dose necessary for their elicitation was increased in all age groups. These differences reached statistical significance in 12-, 18- and 25-day-old rats. A lack of effect of PhB against the rhythmic metrazol activity supports the adequacy of this activity as a model of human absences. Differences between the development of antiepileptic and hypnotic effects of PhB (described earlier) suggest two different mechanisms of action.
The action of ethosuximide, valproate and clonazepam against pentylenetetrazol-induced epileptic EEG phenomena was studied in acute experiments in rats with intercollicular brainstem transection. Ethosuximide lost its action against both rhythmic metrazol activity (model of human absences) and EEG seizures. On the contrary, the action of valproate and clonazepam in cerveau isolé rats was the same as in intact animals. The site of anticonvulsant action of ethosuximide may be localized in hindbrain structures, whereas the actions of both valproate and clonazepam may be demonstrated even if hindbrain structures had been eliminated.