Selective suppression of excessive GluN2C expression rescues early epilepsy in a tuberous sclerosis murine model.

Tuberous sclerosis complex (TSC), caused by dominant mutations in either TSC1 or TSC2 tumour suppressor genes is characterized by the presence of brain malformations, the cortical tubers that are thought to contribute to the generation of pharmacoresistant epilepsy. Here we report that tuberless heterozygote Tsc1(+/-) mice show functional upregulation of cortical GluN2C-containing N-methyl-D-aspartate receptors (NMDARs) in an mTOR-dependent manner and exhibit recurrent, unprovoked seizures during early postnatal life (

[The synthetic cannabinoid analog WIN 55,212-2 potentiates the amplitudes of glycine-activated currents].

Most of the pharmacological actions of cannabinoids are mediated by CB1 receptors. There is also evidence that these compounds can produce effects that are not mediated by the activation of identified cannabinoid receptors. Our data demonstrate that cannabinoids may directly affect the functioning of inhibitory glycine receptor (GlyR) channels. Here, we report that cannabinoid receptors agonist WIN 55,212-2, in a CB1 receptor independent manner, cause a significant potentiation of the amplitudes of glycine-activated currents (I(Gly)) in acutely isolated hippocampal CA3 and CA1 pyramidal neurons. The maximal potentiation by this compound was observed at the lowest concentration of glycine; with increasing concentrations of glycine, the potentiation significantly decreased. Also WIN 55,212-2 significantly accelerated the desensitization of Gly-induced chloride current and significantly decreased the rise time. The effects of WIN 55,212-2 on I(Gly) were not attenuated in the presence of CB1 receptor antagonist AM251, suggesting that CB1 receptor activation are not involved in action of cannabinoid on GlyRs. Altogether these data allow us to suggest the existence of a CB1R independent action of cannabinoids directly on glycine-activated currents, representing a novel antinociceptive mechanism of this compounds.

[Autoregulation of cerebral blood flow in condition of experimental hepatic encephalopathy].

The linear interrelation between Systemic Arterial Blood Pressure and local Cerebral Blood Flow has been shown in experiments on rats with induced experimental hepatic encephalopathy. This is evidence of complete malfunctioning of the mechanism of Cerebral Blood Flow Autoregulation. Quantitative comparison of local Cerebral Blood Flow intensity in control and experimental (Hepatic Encephalopathy) animals has shown significant increase of the basic level of cerebral blood flow in rats with induced Hepatic Encephalopathy (p<0,05). On the basis of own and literature data the chain of developments in experimental hepatic encephalopathy was drawn: excess of Nitric Oxide because of hepatic failure can cause the cerebral vasodilatation with inadequate increase of cerebral blood flow intensity, resulting in malfunction of the cerebral blood flow autoregulation, increase of Blood Brain Barrier permeability, and penetration of toxic substances in nervous tissue. As a result of these--cognitive deficiency is developed (at the best) and hepatic coma (at the worst).

[Diadenosine polyphosphate analogue modulates signal transduction in hippocampal slices].

The modulatory effect of endogenous diadenosine polyphosphates on synaptic transmission in the rat hippocampal slices has been re-examined with a non-hydrolysable Ap4A analogue diadenosine-5',5'>>-P1,P4-[beta,gamma-methylene]tetraphosphate (AppCH2ppA). We have shown that AppCH2ppA at low micromolar concentrations induce inhibition of orthodromically evoked population spikes, without affecting of excitatory postsynaptic currents and antidromic spikes recorded in the CA1 zone of hippocampus. Such a spatially selective neuronal inhibition may influence dendritic electrogenesis in pyramidal neurons and consequently mediate control of neuronal network activity in hippocampus.

[Changes in emotional state and learning process disorders in rats with experimental hepatic encephalopathy].

Animal models of liver failure are widely used for research of morphological and functional changes and pathogenetic mechanisms of hepatic encephalopathy. Changes in learning process and emotional state of rats, which were administered intraperitoneally (Phenobarbiton 40 mg/kg/day) for five days and then subcutaneously (Acetaminophen 1000 mg/kg) are described. Behaviour of rats was studied in the "open field". Experimental animals in comparison with the control group had decreased position-finding-exploring activity although the motor activity and the fear feeling level weren't changed. The testing in the multi branch maze showed that the experimental animal's learning ability was greatly decreased--from the start platform of the maze to the nest they made more mistakes and spent more time than the control group animals, and even at the end of the maze session successful completion of task (to reach the nest) wasn't exceeding 60%.

[Altered ability to learn of rat offspring with iodine deficiency].

Experimental data demonstrate that hypothyroidism could result in depressive behavior and subsequently thyroid hormones could act as antidepressants. Postnatal changes in learning ability, memory and emotional status in posterity of rats, which have experienced different level of iodine deficiency before conception and during all gestation period were investigated in this study. Results obtained suggest that sudden iodine deprivation before and during gestation led to a significant neurological defect, which was represented by loss of ability to learn, one of the most important functions of brain in newborn and by evidence of depression. Iodine supply to the diet of female rats eliminates these effects completely.

[Employment of the laser apparatus SL-30 in complex treatment of chronic recurrent herpetic stomatitis].

The purpose of the study was the estimation of complex treatment effectiveness of chronic recurrent herpetic stomatitis using portable laser device "Beurer" (Germany). Fifty patients 17 till 55 years of age were investigated. Among them 28 were women and 22 were men. They were divided into two groups. All patients were treated by standard algorithm according to the severity of the disease. In the patients from the second group laser therapy by means of SL-30, 15-30 min per day was administered. After the completion of the course of treatment positive therapeutic effect has been achieved in all patients from the second group. Disappearance of the subjective symptoms and the initiation of the reparative-regenerative processes has occurred much faster in this group which gave us an opportunity to reduce the number of sessions by 5-6 in comparison with the first group. Thus, it was shown that the use of apparatus SL-30 in complex treatment of the chronic recurrent herpetic stomatitis increases the efficiency of the treatment.

[The models of hepatic insufficiency and encephalopathy in animals].

The majority of the investigation methods of biochemical, morphological and metabolic disorders in hepatic insufficiency and encephalopathy occurrence are inadequate in use in clinical conditions because their invasiveness frequently creates dangerous situations to the patient life and health. That's why, to characterize the mechanisms, constituting the hepatic and cerebral damages base, for testing of a new medicinal preparations, aprobation of a new theoretical and clinical hypotheses, the models of an acute and chronic hepatic insufficiency are applied on the animals, permitting to unify the age, genetic peculiarities and physiological parameters of the individuals involved in experiments, the pathology character, its severity and longevity. Homogeneity of these indexes permits to estimate molecular, structural and functional disorders, laying in the base of pathological process. We have analyzed the experimental models of hepatic insufficiency, basing on the hepatotoxins usage--acetaminophen (paracetamol), carbon tetrachloride, thioacetamide, D-galactosamine, concanavalin A, lipopolysaccharides. Every existing pharmacological model of hepatic insufficiency and encephalopathy for animals owes its own advantages and faults. The choice of a model depends on tasks of the investigation and of the animal species, involved in the procedures.

Modulation of ion channels in rat neurons by the constituents of Hypericum perforatum.

Despite almost forty years of widespread use of antidepressant drugs, their mode of action is still unknown. Hyperforin, a phloroglucinol derivative, is a major pharmacologically and therapeutically active constituent of Hypericum perforatum extract that is widely used as an herbal antidepressant drug. However, the mechanism or mechanisms of action of these naturally abundant, non-toxic extracts remain unclear. Enzymatically isolated patch-clamped rat central and peripheral neurons exposed to rapid changes in the composition of external medium (concentration clamp) were used in our experiments to investigate the modulation of the various voltage- and ligand-gated channels by hyperforin, as well as by other constituents of Hypericum perforatum. At nanomolar concentrations, hyperforin induced significant inhibition of various ion channels. In the case of P-type Ca2+ channels, we established that hyperforin acts via interaction with calmodulin or through calmodulin-activated pathways involving at least one second messenger. The results presented here indicate that multiple mechanisms and extract constituents may be involved in the antidepressant action of Hypericum extracts, and that they could also possess neuroprotective and analgesic effects.

New channel blocker BIIA388CL blocks delayed rectifier, but not A-type potassium current in central neurons.

A new substance (R,S)-(3,4-dihydro-6,7-dimethoxyisoquinoline-1-yl)-2-cyclohexyl-N-(3,3-diphenylpropyl)-acetamide hydrochloride (BIIA388Cl), which demonstrates neuroprotective properties in animal models, was examined for its action on K(+) currents in acutely isolated rat hippocampal neurons using the patch-clamp/concentration clamp techniques in the whole-cell configuration. The delayed rectifier K(+)-current (I(DR)) was strongly inhibited by externally applied BIIA388Cl, while the transient A-current (I(A)) remained virtually unaffected. Block of I(DR) by the pre-applied BIIA388Cl was revealed as a rapid decay of the current indicating direct interaction of the drug with the open state of the channel. The removal of the block upon repolarization was also rapid (tau=22 ms). The dose-response relationship for the blocking action of BIIA388Cl revealed an IC(50) value of 300 nM for the peak I(DR), whereas the IC(50) value for I(DR) measured 300 ms after the onset of depolarization was 120 nM. The blocking action of BIIA388Cl on I(A) was at least 200 times less potent. These data allow us to conclude that BIIA388Cl is an effective and selective blocker of I(DR). This current is the main pathway for the loss of intracellular potassium by depolarized neurons. Selective obstruction of this pathway could be useful for neuroprotection.

Hyperforin modulates gating of P-type Ca2+ current in cerebellar Purkinje neurons.

Whole-cell, patch-clamp recordings from acutely isolated cerebellar Purkinje neurons demonstrate a two-stage modulation of P-type high-voltage-activated (HVA) Ca2+ current by a constituent of St. John's wort, hyperforin (0.04-0.8 microM). The first stage of modulation was voltage dependent and reversible. It comprised slow-down of the activation kinetics and a shift in the voltage dependence of P-current to more negative voltages. Hyperforin (0.8 microM) shifted the maximum of the current/voltage (I/V) relationship by -8+/-2 mV. The second, voltage-independent stage of modulation was manifested as a slowly developing inhibition of P-current that could not be reversed within the period of study. Neither form of modulation was abolished by intracellular guanosine 5'-O-(2-thiodiphosphate) (GDPPS) or guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS) or by strong depolarising pre-pulses, indicating that modulation via guanine nucleotide-binding proteins (G proteins) is not involved in the observed phenomenon. Calmidazolium (0.5 microM), an antagonist of the intracellular Ca2+-binding protein calmodulin significantly inhibited the hyperforin-induced shift of the IIV curve maximum and the slow-down of the activation kinetics. It did not, however, affect the delayed inhibition of P-current, indicating that the two stages of modulation are mediated by separate mechanisms.

NMDA receptor-mediated synapses between CA1 neurones: activation by ischaemia.

Using an in situ patch clamp in hippocampal CA1 mini-slices, we measured excitatory postsynaptic currents (EPSC) by varying the strength of the stimulus applied to the axons of CA3 neurones. The kinetics of the EPSC was initially independent of the stimulus strength. Post-ischaemic potentiation of the EPSC was observed 60-80 min after brief periods (10 min) of anoxia/aglycaemia. The decay of the EPSC slowed significantly in most of the examined neurones. In 11 of 17 cells the EPSC kinetics became dependent on stimulus strength: a slower decay corresponded to a stronger stimulus. This effect was not abolished by N-methyl-D-aspartate (NMDA) or a non-NMDA receptor blocker (D-2-amino-5-phosphonovaleric acid or 6-cyano-7-nitroquinoxaline-2,3-dione respectively) indicating the polysynaptic nature of the modified EPSC: transient ischaemia led to the long-term recruitment of previously inactive, possibly latent NMDA synapses between CA1 neurones.

Latent N-methyl-D-aspartate receptors in the recurrent excitatory pathway between hippocampal CA1 pyramidal neurons: Ca(2+)-dependent activation by blocking A1 adenosine receptors.

When performed at increased external [Ca2+]/[Mg2+] ratio (2.5 mM/0.5 mM), temporary block of A1 adenosine receptors in hippocampus [by 8-cyclopentyltheophylline (CPT)] leads to a dramatic and irreversible change in the excitatory postsynaptic current (EPSC) evoked by Schaffer collateral/commissural (SCC) stimulation and recorded by in situ patch clamp in CA1 pyramidal neurons. The duration of the EPSC becomes stimulus dependent, increasing with increase in stimulus strength. The later occurring component of the EPSC is carried through N-methyl-D-aspartate (NMDA) receptor-operated channels but disappears under either the NMDA antagonist 2-amino-5-phosphonovaleric acid (APV) or the non-NMDA antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). These findings indicate that the late component of the SCC-evoked EPSC is polysynaptic: predominantly non-NMDA receptor-mediated SCC inputs excite CA1 neurons that recurrently excite each other by predominantly NDMA receptor-mediated synapses. These recurrent connections are normally silent but become active after CPT treatment, leading to enhancement of the late component of the EPSC. The activity of these connections is maintained for at least 2 hr after CPT removal. When all functional NMDA receptors are blocked by dizocilpine maleate (MK-801), subsequent application of CPT leads to a partial reappearance of NMDA receptor-mediated EPSCs evoked by SCC stimulation, indicating that latent NMDA receptors are recruited. Altogether, these findings indicate the existence of a powerful system of NMDA receptor-mediated synaptic contacts in SCC input to hippocampal CA1 pyramidal neurons and probably also in reciprocal connections between these neurons, which in the usual preparation are kept latent by activity of A1 receptors.