Non-classic effects of luliberin confirming the pleiotropy of neuropeptides

The effects of synthetic neuropeptide LH-RH and its analogues were studied in experiments on 174 white male rats. The influence of the substances was shown on instrumental avoidance learning in Y-shaped maze. Convulsive and anticonvulsive effects of the preparations were studied on experimental model of corasol seizures. The analgetic effect of the substances was evaluated by behavioural pain reaction to electrical stimulation of the tail root. Analgetic, anticonvulsive, and psychostimulating LH-RH properties confirm polyfunctionality and "pleiotropy" of neuropeptides as a class of new endogenous informational compounds.     

Effects of phenazepam and aliphatic alcohols on epileptic complex created in the rat brain cortex

Effects of phenazepam and aliphatic alcohols (methanol, ethanol, butanol, and propanol) on associated epileptic complex created in the rat brain cortex by applications of strychnine were studied. Phenazepam considerably suppressed the epileptic foci and their complexes in a dose-dependent manner. A comparison of anticonvulsive effects in a series of aliphatic alcohols methanol-ethanol-propanol-butanol showed that all these substances are potent anticonvulsants. Propanol and butanol reduce epileptic seizures most intensively, but, at the same time, they are most toxic. Application of labelled⁴C-ethanol showed that anticonvulsive effects strongly correlate with changes in the ethanol concentration in the blood.Neirofiziologiya/Neurophysiology, Vol. 26, No. 6, pp. 443–448, November–December, 1994.     

Effects of anticonvulsive substances on Na,K-ATPase from the synaptic membranes of animal brain]

The distribution pattern of marker enzymes (Na, K-ATPase, acetylcholinesterase) in three fractions of synaptic membranes (SM) of rat brain were studied. The effects of three anticonvulsive agents on Na, K-ATPase from the total fraction of rat brain SM and purified membrane preparation from ox brain were estimated by different methods. Under optimal conditions (Na/K = 5) diphenylhydantoin (DPH) at a concentration of 0,1 mM activates Na, K-ATPase from the total SM fraction only in the absence of ouabain, whereas carbamazepine and pyrroxane taken at the same concentrations have no effect on Na, K-ATPase, irrespective of the type of the enzyme assay. DPH seems to compete with ouabain. Under non-optimal ionic conditions (Na/K = 250) all the anticonvulsive substances studied inhibit Na, K-ATPase of the total SM fraction. The mixture of hydrophobic agents (propylene glycol and ethanol) used to dissolve carbamazepine inhibits Na, K-ATPase from the total SM fraction only under non-optimal conditions. The inhibiting effect of the anticonvulsive substances under study on Na, K-ATPase from the purified membrane preparations is maximal at the concentration of 10(-6) M; at higher concentrations the effect is less pronounced.     

Role of neuropeptides in the mechanisms of chronic epileptization of the brain

We describe experimental studies of the anticonvulsive effects of neuropeptides from the kyotorphin family (kyotorphin, neokyotorphin, and 2-ser-neokyotorphin) and galanin tested in a model of picrotoxin-induced kindling in rats. Intraventricular injections of the above neuropeptides demonstrated their clear anticonvulsive efficacy: the latency of the first convulsive reactions increased, and the intensity of seizures decreased. A protective efficacy of these peptides observed under conditions of the kindling model (which is the most steady with respect to the effects of antiepileptic drugs, and whose phenomenology is the closest to clinical manifestations of epilepsy) allows us to believe that further studies of anticonvulsive action of the peptides is expedient.     

Effector modeling of the action of ligands of GABA-receptor complex. Functional interaction of the hypothetic alcohol receptor with other subunits of the complex

The types of the interaction of the pharmacological effects of ethanol and barbiturate antagonists--picrotoxin, bemegride and corasol--were determined. The effect of ethanol was determined as competitive--for the convulsant effects of bicuculline, and non-competitive--for the effects of thiosemicarbazide. The indices of the anticonvulsant effects of n-aliphatic alcohols were compared. It is suggested that n-aliphatic alcohols alter the functional status of the supramolecular GABA-receptor channel ensemble. The pharmacological properties and the elements of the structural similarity of picrotoxin and n-propanol (the presumptive ligand of the GABA-receptor channel ensemble) are discussed.     

Convulsions induced by submaximal dose of pentylenetetrazol in mice are antagonized by the benzodiazepine antagonist Ro 15-1788

The effects of benzodiazepine antagonist Ro 15–1788, alone or with diazepam, were studied in mice on convulsions induced by pentylenetetrazol (PTZ). We found that Ro 15–1788 (1 mg/kg) was able to antagonize the anticonvulsive effects of diazepam (1 mg/kg), but also had, with submaximal doses of PTZ (65 mg/kg), its own anti-convulsive action. At very low doses (0.1 mg/kg), it even potentiated the anticonvulsive effects of diazepam (0.05 mg/kg). This dual action provides evidence for partial agonist properties of the antagonist Ro 15–1788.     

Anticonvulsive effect of the cerebrospinal fluid of cats with epileptic status

We studied the properties of the cerebrospinal fluid obtained from the cats with a formed epileptic status. Samples of such fluid were injected into the rats, in which later on such epileptic status was modeled. The clearly expressed anticonvulsive efficacy of such cerebrospinal fluid is demonstrated; it was manifested in a decrease of the duration of seizure reactions and prevention of the development of generalized clonico-tonic attacks. It is concluded that this effect is not species-specific, and the possible nature of an anticonvulsive profile of the fluid is discussed.     

Effector modeling of the action of GABA-receptor complex ligands. Functional interactions of subunits of the complex

The distribution of the minimum effective doses of bicuculline, corasole and picrotoxin was studied in intact mice and in mice administered different doses of 1.4-benzodiazepines (phenazepam and its 1,2,4,5-tetrahydroxy derivatives) and sodium barbital. The changes in the "dose-response" relationship for thiosemicarbazide have been observed with the administration of the increasing doses of phenazepam and sodium barbital. The effects registered correspond to the modifications of the GABA-receptor complex by exogenous ligands. The forms of the "dose-response" relationship observed, the types of the antagonism between pharmacological agents and the cooperation of their interaction correspond to the indices obtained from the "quartet" model of the receptor-channel complex.     

Effector modelling of the action of ligands of the GABA-receptor complex, cooperativity of the processes and the type of modification of the complex by convulsants and their reversible agonists

The expression of cooperativity of pharmacological effects of convulsants--exogenic ligands of supramolecular GABA-receptor-channel ensemble (GABA-RC)--bicuculline, picrotoxin, pentylenetetrazole, bemegride at intravenous infusion to intact animals and against a background of administration of barbital-Na and phenazepam is determined. The supposed mechanism of bemegride effect is discussed. Analysis of principles of GABA-RC functioning in vivo on the base of pharmacological data (cooperativity coefficients and types of modulation of GABA-RC functions at the interaction of convulsants and their reverse agonists) suggests the formation of biosystem response at modification of structures adequate to one of four subunits of "quartet" (tetrameric) model of GABA-RC.     

Effector modeling of the action of ligands of the GABA receptor complex: functional interactions of muscimol and exogenous modulators of the complex]

In comparison with the literature data the pharmacological effects of muscimol (MS) on mice organism were studied under the condition of administration of the exogenic ligands of GABA-receptor complex GABA antagonist bicuculline (BC), chloride ionophor blocking agent pentylenetetrazole (PZ), phenazepam (BD), sodium barbital (BB) and GABA synthesis antagonist--thiosemicarbazide (TS). Antagonism of MS to the anticonvulsant effect of BB and BD at the administration of BC to the animal was observed, while no effect was observed at the administration of PZ. However at the administration of TS to the experimental animals MS exhibits anticonvulsant effect. The observed properties (partial agonism/partial reverse agonism) of MS at its effect to the whole system are probably determined by the level of endogenic GABA and its changes due to the administration of TS and functional state of GABA--receptor system modified with the exogenic ligand BC.     

Dampening of Hyperexcitability in CA1 Pyramidal Neurons by Polyunsaturated Fatty Acids Acting on Voltage-Gated Ion Channels

A ketogenic diet is an alternative treatment of epilepsy in infants. The diet, rich in fat and low in carbohydrates, elevates the level of polyunsaturated fatty acids (PUFAs) in plasma. These substances have therefore been suggested to contribute to the anticonvulsive effect of the diet. PUFAs modulate the properties of a range of ion channels, including K and Na channels, and it has been hypothesized that these changes may be part of a mechanistic explanation of the ketogenic diet. Using computational modelling, we here study how experimentally observed PUFA-induced changes of ion channel activity affect neuronal excitability in CA1, in particular responses to synaptic input of high synchronicity. The PUFA effects were studied in two pathological models of cellular hyperexcitability associated with epileptogenesis. We found that experimentally derived PUFA modulation of the A-type K (K_A) channel, but not the delayed-rectifier K channel, restored healthy excitability by selectively reducing the response to inputs of high synchronicity. We also found that PUFA modulation of the transient Na channel was effective in this respect if the channel''s steady-state inactivation was selectively affected. Furthermore, PUFA-induced hyperpolarization of the resting membrane potential was an effective approach to prevent hyperexcitability. When the combined effect of PUFA on the K_A channel, the Na channel, and the resting membrane potential, was simulated, a lower concentration of PUFA was needed to restore healthy excitability. We therefore propose that one explanation of the beneficial effect of PUFAs lies in its simultaneous action on a range of ion-channel targets. Furthermore, this work suggests that a pharmacological cocktail acting on the voltage dependence of the Na-channel inactivation, the voltage dependences of K_A channels, and the resting potential can be an effective treatment of epilepsy.     

Tofizopam selectively increases the action of anticonvulsants

The effect of tofizopam, a 3,4-benzodiazepine (BZ) derivative, in modulating the anticonvulsive action of various drugs was investigated in mice. Electric shock and intravenous infusion of bicuculline were used as convulsive agents. Tofizopam increased the action of clonazepam, diazepam and flunitrazepam against bicuculline. The anticonvulsive effect of diazepam against electroshocks was augmented only slightly. Tofizopam failed to alter the actions of carbamazepine, phenobarbital, phenytoin, or sodium valproate against either of the convulsive stimuli. Both in vitro and in vivo, tofizopam has been shown to stimulate the binding of 1,4-BZs (e.g., flunitrazepam) to BZ receptors. Similarly, tofizopam enhances the binding of muscimol to GABA receptors. Although several anticonvulsants act on the GABA-BZ receptor complex, tofizopam seems to modify selectively the anticonvulsive action of 1,4-BZs, and this effect is seen better in bicuculline-induced seizures than in electroshocks.     

Depressive effects on the central nervous system and underlying mechanism of the enzymatic extract and its phlorotannin-rich fraction from Ecklonia cava edible brown seaweed

Marine plants have been reported to possess various pharmacological properties; however, there have been few reports on their neuropharmacological effects. Terrestrial plants have depressive effects on the central nervous system (CNS) because of their polyphenols which make them effective as anticonvulsants and sleep inducers. We investigated in this study the depressive effects of the polyphenol-rich brown seaweed, Ecklonia cava (EC), on CNS. An EC enzymatic extract (ECEE) showed significant anticonvulsive (>500 mg/kg) and sleep-inducing (>500 mg/kg) effects on the respective mice seizure induced by picrotoxin and on the mice sleep induced by pentobarbital. The phlorotannin-rich fraction (PTRF) from ECEE significantly potentiated the pentobarbital-induced sleep at >50 mg/kg. PTRF had binding activity to the gamma aminobutyric acid type A (GABA(A))-benzodiazepine (BZD) receptors. The sleep-inducing effects of diazepam (DZP, a well-known GABA(A)-BZD agonist), ECEE, and PTRF were completely blocked by flumazenil, a well-known antagonist of GABA(A)-BZD receptors. These results imply that ECEE produced depressive effects on CNS by positive allosteric modulation of its phlorotannins on GABA(A)-BZD receptors like DZP. Our study proposes EC as a candidate for the effective treatment of neuropsychiatric disorders such as anxiety and insomnia.     

Inhibitory processes in the cerebral cortex and the anticonvulsive action of benzodiazepine derivatives]

A comparative study of the effect of some benzodiazepine deprivatives (chlonazepam, lorazepam, diazepam, and medazepam) on the recovery cycles of the interzonal response was carried out on unanesthetized curare-immobilized cats. These drugs proved to selectively inhibit the testing potential within the range of 20 to 100 msec. between the conditioning and the testing stimuli. This indicates that potentiation of GABA-ergic inhibition in the cerebral cortex. The threshold doses of the drugs inducing the depression of the test response and of ED50, preventing the development of convulsions, caused by GABA deficiency or by GABA-ergic receptor block, were compared; a correlation between the mentioned effects was demonstrated. The significance of GABA-positive effect of benzodiazepines in the mechanism of their anticonvulsive activity is suggested.     

Anticonvulsive properties of enomelanin

Antiepileptic effects of enomelanin (natural oligomer obtained from pressed grapes) were analysed on the models of focal and clonic-tonic epileptic activity (EA). Electrocorticographic and motor manifestations of EA have been studied. Enomelanin in EA models used was shown to possess marked anticonvulsive properties.     

Optimization of the composition of the radioprotective complex APAETP+mexamine and analysis of its action

The method of mathematical theory of experiment was used to find optimum variants of the radioprotective complex APAETP + mexamine. The character of their pharmacological interaction, depending on their dose ratio, was determined. It is suggested that it is conditioned by the specific role of different mechanisms involved in the radioprotective effect.     

Synthesis,in-vitro cholinesterase inhibition,in-vivo anticonvulsant activity and in-silico exploration of N-(4-methylpyridin-2-yl)thiophene-2-carboxamide analogs

In our current research, a diverse effect of acetylcholinesterase inhibitors was studied on BALB-C mice by using pentylenetetrazole (PTZ) seizure model. A series of carboxamide analogs (4a–4i) have been synthesized via Suzuki coupling reaction in moderate to good yields (35–84%). To study the efficacy of the synthesized compounds against AD, in-vitro inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) was performed. A number of compounds showed inhibition in low micromolar range. Subsequently, these compounds were evaluated for anticonvulsive effects in BALB-C mice by using pentylenetetrazole (PTZ) seizure model. The compound 4e displayed potential anticonvulsive effect and displayed 50% and 80% protection from mortality at the dose of 10 mg/kg, and 30 mg/kg respectively. The compound 4h showed some protection (33%) from mortality at 10 mg/kg and was not further explored based on non-significant delay in onset of myoclonic seizures. While, other compounds from the series did not show any anticonvulsive activity. To rationalize the observed biological activity, we performed docking studies against AChE and BChE targets. To explore the rationale of the mechanism of in-vivo anticonvulsant activity, docking studies were performed on GABAergic receptors. Moreover, in order to establish a relationship between physiochemical data of the synthesized compounds and their in-vivo performance, we employed in-silico pharmacokinetic predictions. Our in-silico predictions suggest that the plasma protein binding, low to moderate blood brain barrier penetration and low solubility are the main attributes of low in-vivo performance.     

Multiple treatment potentiates the anticonvulsive activity of cholecystokinin octapeptides

The dose-response curves for the anticonvulsive activity of sulfated and nonsulfated cholecystokinin octapeptide (CCK-8-SE and CCK-8-NS) against picrotoxin-induced (6 mg/kg SC) seizures were assessed either following or without pretreatment with a single high dose of CCK-8-SE or CCK-8-NS, to examine acute tolerance to the effect after IP injections in mice. As CCK-8-SE or CCK-8-NS pretreatment, a 1.6 μmole/kg dose was injected 2 hr prior to the second injection. No acute tolerance to the anticonvulsive activity was demonstrated, and CCK-8-NS pretreatment significantly potentiated its own anticonvulsive activity. Chronic (8-day) daily treatment with a 0.16 μmole/kg dose of CCK-8-SE or CCK-8-NS antagonized seizures by picrotoxin, presumably in a cumulative manner. To investigate the interactions of CCK octapeptides with other anticonvulsive agents, picrotoxin-induced seizures were antagonized with several doses of diazepam following or without acute, high-dose pretreatment with CCK-8-SE or CCK-8-NS. The two octapeptides only slightly modified the activity of diazepam: CCK-8-SE pretreatment displayed a tendency to antagonize it, while CCK-8-NS pretreatment to potentiate it. The results suggest that multiple treatment with CCK-8 induces sensitization of CCK receptors mediating anticonvulsive activity.     

Pharmacological and neurochemical characterization of the involvement of hippocampal adrenoreceptor subtypes in the modulation of acute limbic seizures

Noradrenaline exerts inhibitory effects on seizure susceptibility. Subtype selective agonists and antagonists were used to identify the anticonvulsant hippocampal adrenoreceptors. Intrahippocampal dialysis was used for administration of all compounds, including pilocarpine for limbic seizure induction, and as the neurotransmitter sampling tool. The noradrenaline reuptake inhibitor maprotiline mediated anticonvulsant effects, associated with dose-dependent increases in extracellular hippocampal noradrenaline, dopamine and GABA levels. At high concentrations, maprotiline produced proconvulsant effects associated with high levels of noradrenaline, dopamine and glutamate. Maprotiline's anticonvulsant effect was blocked by administration of either a selective α(2) - and β(2) -antagonist. α(2) -Antagonist administration with maprotiline was associated with a further increase in noradrenaline and dopamine from maprotiline alone; whereas β(2) -antagonist administered with maprotiline inhibited the dopamine increases produced by maprotiline. α(1A) -Antagonism blocked the GABA-ergic but not the anticonvulsive effect of maprotiline. These results were confirmed as combined but not separate α(2) - and β(2) -adrenoreceptor stimulation, using selective agonists, inhibited limbic seizures. Interestingly, α(1A) -receptor stimulation and α(1D) -antagonism alone also inhibited seizures associated with respectively significant hippocampal GABA increases and glutamate decreases. The main findings of this study are that (i) increased hippocampal noradrenergic neurotransmission inhibits limbic seizures via combined α(2) - and β(2) -receptor activation and (ii) α(1A) - and α(1D) -adrenoreceptors mediate opposite effects on hippocampal excitability.     

Analysis of the structure of the components of the convulsive action of corazole following administration of sulazepam and its metabolites to mice]

A study was made of the interrelationship between the minimal effective doses of pseudoclonic and clonico-tonic convulsions, and also tonic extension caused by the intravenous injection of corazol to mice and the effect of anticonvulsive action of sulazepam and its metabolites (diazepam, desmethyldiazepam and oxadiazepam) on this process. It was shown that all the compounds under study increased the values of the minimal effective doses by the recorded indices of the convulsive seizure, whereas the maximum of the anticonvulsive activity was reached 15 minutes after the sulazepam and oxazepam, and 5 to 30 min after diazepam administration. There proved to be a distinct correlation between the minimal effective doses values of the recorded indices of the confulsive seizure in the control animals which also persisted after the administration of the agents under study. It is supposed that sulazepam and its metabolites increased the minimal effective doses of corazol for the recorded effects, but failed to alter the general picture of the convulsive attack and did not influence the dispersion corazol dose-effect dependence.