[Decreased acetylcholinesterase activity in the area of epileptogenic foci created by met-enkephalin in the hippocampus of rats]. / Snizhenie aktivnosti atsetilkholinesterazy v oblasti épileptogennykh ochagov, sozdannykh met-énkefalinom v gippokampe krys.

Experiments on rats with electrochemotrodes implanted in the left and right hippocamp have shown that in epileptogenic foci created by microinjections of met-enkephalin or D-ala-2-met-enkephalin into the hippocamp, acetylcholinesterase activity (AChE) was diminished. It is assumed that reduction in AChE activity is an adaptive mechanism by which the excitability of hippocampal inhibitory basket cells, which are sensitive to acetylcholine, is increased.

[A change in hippocampal excitability in rabbits of different ages under the influence of serotoninergic system stimulation]. / Izmenenie vozbudimosti gippokampa krolikov raznogo vozrasta pod vliianiem stimuliatsii serotoninergicheskikh sistem

In adult, 6-10 days, and 16-20 days old rabbits with electrochemotrodes implanted into the left and right dorsal hippocampus, 5-methoxytriptamine (mexamine, 8 mg/kg, i.p.) stimulation of the central serotoninergic systems decreased the amount of seizures in the hippocampal penicilline epileptogenic focus in 6-10 and 16-20 days old rabbits and had no effect on interictal epileptiform discharges in the EEG. After i.v. mexamine administration (2 mg/kg) in 16-20 days old rabbits, both the inhibition of seizures and the interictal epileptiform activity in the EEG occurred. In adult rabbits, mexamine (2 mg/kg i.v.) had no effect on the hippocampus epileptogenic foci. The level of the serotoninergic systems activity is supposed to be more significant for supporting the hippocampus excitability in young rabbits than in adult ones.

[Age peculiarities in the effect of M- and N-cholinolytics on the activity of the epileptogenic zone in the rabbit hippocampus]. / Vozrastnye osobennosti vliianiia M- i N-kholinolitikov na aktivnost' epileptogennogo ochaga v gippokampe krolikov

In experiments on 6-10, 16-20-day and adult rabbits, electrochimiotrodes were chronically implanted into the dorsal hippocamp. Direct application of a M-cholinolytic, metamizyl, or N-cholinolytic, gangleron, to penicillin-induced epileptogenic zone in the hippocamp inhibited seizures in rabbits of all age groups. The intensity of interseizure epileptiform discharges in the EEG did not change under the action of cholinolytics in adult and 6-10-day rabbits, and decreased in 16-20-day ones. Parenteral administration of gangleron caused the same effect on the activity of epileptogenic zone, as its direct application to the hippocamp. Parenteral administration of metamizyl inhibited seizures in young animals (similarly to its direct application to the hippocamp), but increased the seizures and interseizure discharges in adult rabbits. Therefore, already to the 6th day of postnatal life of rabbits, blocking of the cholinoreactive system of the hippocamp may inhibit circulation of seizural discharges along closed neuronal circuits, which is necessary for the formation of the seizure.

[Age peculiarities of trace discharges of after-effect and of the activity of epileptogenic zone in the hippocamp of rabbits]. / Vozrastnye osobennosti sledovykh razriadov posledeistviia i aktivnosti epileptogennogo ochaga v gippokampe krolikov

Seizure activity in the hippocamp has been studied on 6-10-, 16-20-day and adult rabbits. The pattern and thresholds of trace discharges of after-effect evoked by the electrical stimulation of the hippocamp were found to be similar in animals of all age groups. However, the amplitude of after-discharges significantly increased during the development of the brain. After the formation of penicillin epileptogenic zone in the hippocamp, EEG of all animals exhibited the identical types of focal interseizure discharges and electrographic correlates of seizures, yet the amplitude of epileptifiorm discharges on the EEG increased with age. Contralateral hippocamp was involved into the pathological process more easily in young rabbits than in adult ones.