High-fructose intake-induced dyslipidemia and oxidative stress accompanied by hippocampal dysfunctions in hypertensive but not hypertriacylglycerolemic rats.

A high-fructose intake is metabolically analogous to a high-fat diet. The impact of highfructose intake was investigated in spontaneously hypertensive (SHR) and hypertriacylglycerolemic (HTG) rats to find out the impact of which risk factor of metabolic syndrome - hypertension or hypertriacylglycerolemia - will cause more complications. Rats were fed a standard or a fructose diet (F60) with 60% of added fructose for 5 weeks. The F60 diet increased the total serum cholesterol content of both HTG-F60 and SHR-F60 rats. Further, in SHR-F60 it increased serum triacylglycerols, TBARS in the liver, a specific activity of NAGA in the kidney, aggravated glucose tolerance, deteriorated synaptic plasticity, and reduced somatic and dendritic responses in the hippocampus. SHR rats were more sensitive to the F60 diet, suggesting that hypertension along with a high-fructose intake result in a more pronounced disorder compared to hypertriacylglycerolemia. This work wants to draw attention to fructose-induced health risks associated with hypertension.

Effect of handling on ATP utilization of cerebral Na,K-ATPase in rats with trimethyltin-induced neurodegeneration.

Previously it was shown that for reduction of anxiety and stress of experimental animals, preventive handling seems to be one of the most effective methods. The present study was oriented on Na,K-ATPase, a key enzyme for maintaining proper concentrations of intracellular sodium and potassium ions. Malfunction of this enzyme has an essential role in the development of neurodegenerative diseases. It is known that this enzyme requires approximately 50% of the energy available to the brain. Therefore in the present study utilization of the energy source ATP by Na,K-ATPase in the frontal cerebral cortex, using the method of enzyme kinetics was investigated. As a model of neurodegeneration treatment with trimethyltin (TMT) was applied. Daily handling (10 min/day) of healthy rats and rats suffering neurodegeneration induced by administration of TMT in a dose of (7.5 mg/kg), at postnatal days 60-102 altered the expression of catalytic subunits of Na,K-ATPase as well as kinetic properties of this enzyme in the frontal cerebral cortex of adult male Wistar rats. In addition to the previously published beneficial effect on spatial memory, daily treatment of rats was accompanied by improved maintenance of sodium homeostasis in the frontal cortex. The key system responsible for this process, Na,K-ATPase, was able to utilize better the energy substrate ATP. In rats, manipulation of TMT-induced neurodegeneration promoted the expression of the α2 isoform of the enzyme, which is typical for glial cells. In healthy rats, manipulation was followed by increased expression of the α3 subunit, which is typical of neurons.

Natural substance rutin versus standard drug atorvastatin in a treatment of metabolic syndrome-like condition.

BACKGROUND: Metabolic syndrome is a cluster of metabolic risk factors. The clear causes of its development are not known yet and there is no comprehensive treatment of this disease. There is a trend to use natural substances in the treatment of various diseases, but their effects need to be well explored. We decided to test effect of rutin compared to the effect of the standard drug atorvastatin. METHODS: As a model of metabolic syndrome we used males of hypertriacylglycerolemic rats in combination with high-fat-high-fructose diet. Rutin (100 mg/kg) and atorvastatin (50 mg/kg) were administered orally daily for 5 weeks. RESULTS: We determined biochemical parameters from blood: HDL-cholesterol, LDL-cholesterol, total cholesterol, triacylglycerols. Relaxation and contraction response of aorta was measured to determine vessel dysfunctions and possible predisposition to cardiovascular disease. The negative influence on cognitive functions could be associated with the development of metabolic cognitive syndrome. Therefore we aimed to monitor spatial memory by Morris water maze test. Both rutin and atorvastatin had a tendency to decrease levels of serum triacylglycerols, but only atorvastatin significantly reduced levels od LDL-cholesterol and increased HDL-cholesterol levels. Both compounds significantly reduced the phenylephrine-induced contractile response of the aorta and improved the relaxation response. Further, treated animals learned better compared to untreated rats in the Morris water maze. CONCLUSION: Based on our results we can assume that atorvastatin and rutin had positive effect on spatial memory and vessel reactivity. Atorvastatin optimized lipid profile of blood serum.

The effect of venlafaxine on blood pressure and ECG in rats fed with high-fat-fructose diet.

Metabolic syndrome represents one of the major health, social and economic issues nowadays, and affects more than 25% people worldwide. Being a multifactorial health problem, metabolic syndrome clusters various features, such as obesity, dyslipidemia, hyperglycemia and hypertension. Each of these disturbances represents a risk factor for developing cardiovascular disease. Moreover, patients with metabolic syndrome are more likely to suffer from depression, thus treatment with antidepressants (e.g. venlafaxine) is often neccessary. However, many of the antidepressants themselves may contribute to worsening or even development of the metabolic syndrome, thus creating a "vicious circle". The aim of this work was to investigate on the animal model of metabolic syndrome, i.e. on hypertriacylglycerolemic rats fed high-fat-fructose diet (HFFD): 1) the effect of a change in diet from HFFD to a standard diet (SD) and the effect of venlafaxine treatment, 2) during HFFD, 3) as well as during a changed diet to SD. We focused on biometric parameters, blood pressure and selected ECG parameters. We observed the reversibility of the present metabolic and cardiovascular changes by switching the HFFD to SD in the last 3 weeks of the experiment. Switch to the standard diet led to decrease of body weight, even in the presence of venlafaxine. Administration of venlafaxine caused the decrease of heart weight/body weight index in rats fed with HFFD compared to the untreated group fed with HFFD for 8 weeks. Blood pressure, which was increased in the HFFD group showed a tendency to decrease to control values after switching to the standard diet . Administration of venlafaxine led to significant increase in all parameters of blood pressure when rats were fed with HFFD throughout the whole experiment. In untreated rats fed with HFFD for 8 weeks, we observed a shorter PQ interval and prolonged QRS complex as well as QTc interval compared to untreated rats with diet switched to SD. This effect was potentiated by venlafaxine administered not only during HFFD but even after switch to SD. Our results point to the fact that metabolic syndrome is clearly affecting the function of the cardiovascular system by modifying blood pressure and electrical activity of the heart. Moreover, administration of venlafaxine may lead to worsening of the observed changes, especially in the presence of high-fat-fructose diet.

Effect of metabolic syndrome on neural plasticity and morphology of the hippocampus: correlations of neurological deficits with physiological status of the rat.

Fat-rich diet (FRD) triggers health complications like hypertension, dyslipidemia, hyperglycemia, insulin resistance and non-alcoholic fatty liver disease, known as the risk factors of metabolic syndrome (MetS), which may result in neurological deficits. The impact of MetS on neuronal functions and brain morphology are poorly understood. We induced MetS-like conditions by exposing hypertriacylglycerolemic (HTG) rats to FRD for eight weeks with the aim to study possible neurological dysfunctions. HTG-FRD rats were compared to HTG rats and Wistar rats on standard diet. The physiological status of the animals was monitored by body, liver and kidney weight. Morphology of the liver, vessel wall and hippocampus were investigated. Basal neurotransmission and synaptic plasticity were measured in the hippocampus ex-vivo. A marked increase of liver weight with marks of steatosis was found in the HTG-FRD group. FRD induced an increase of aortic intima-media thickness. Extracellular recording revealed FRD-induced impairment of long-term potentiation (LTP) at Cornu Ammonis (CA)3-CA1 synapse, contrary to increased presynaptic fiber volley (pV). Reduced thickness of pyramidal cell layer at the CA1 area was found morphometrically. LTP was directly associated with kidney weight and inversely associated with liver weight, pV directly correlated with liver weight, liver/body wt ratio and aortic intima-media thickness. Our results suggest correlations between altered physiological status due to MetS-like conditions and neurological deficits, which may be related with consecutive development of so-called metabolic cognitive syndrome.

Beneficial effect of 6 weeks lasting handling of adult rats on spatial memory in experimental model of neurodegeneration.

Handling is a form of experience which can result in physiological changes depending on the period of postnatal age when performed. There is a lot of evidence about the positive effect of neonatal handling, but a lack dealing with handling of adult rats. Behavioral changes and memory deficits are present in dementia-like disorders. In the present work, we tested whether 6 weeks lasting handling of young adult rats could revert memory impairment induced by trimethyltin (TMT) (7.5 mg/kg, intraperitoneally). Testing rats in Morris water maze revealed significant effect of TMT as well significant effect of handling. We observed improvement of spatial memory also between healthy, non-degenerated rats as well as degenerated rats, represented by shorter latency onto the platform. In our paper, we report beneficial effect of handling on spatial memory that is in compliance with published works about beneficial effect of cognitive therapy and training in patients with early stage of Alzheimer΄s disease and dementia.

In vivo magnetic resonance approach to trimethyltin induced neurodegeneration in rats.

Trimethyltin (TMT) is commonly used to induce neurodegeneration in mice and rats; however, only scarce data of in vivo magnetic resonance (MR) spectroscopy and imaging characterizing TMT neurotoxicity are available. Our aim was to assess brain metabolite changes and brain atrophy by in vivo MR in the rat model of neurodegeneration induced by TMT. Adult male Wistar rats exposed to TMT (8mg/kg, i.p.) were used in the study. Proton MRS was applied on the dorsal hippocampus to reveal changes in neurochemical profile, and MR imaging was used to assess the volume of the entire hippocampus, ventricles and whole brain. Hippocampal levels of N-acetylaspartate (NAA), glutamate (Glu), total creatine (tCr) and taurine (Tau) significantly decreased, while the levels of myo-Inositol (mIns) and glutamine (Gln) significantly increased in TMT treated rats compared to controls. No changes in choline metabolites (tCho), glutathione (GSH), and GABA were observed. MR volumetry revealed a substantial loss of hippocampal mass, cerebral volume shrinkage and ventricular enlargement in the TMT treated group in comparison to the control group. To the best of our knowledge, this is the first study characterizing TMT induced neurodegeneration in the rat by in vivo MRS. Our findings suggest that TMT exposed rats may serve as a reliable animal model of neurodegeneration and MR based parameters could serve as potential in vivo biomarkers of therapeutic response.

Pyridoindole SMe1EC2 as cognition enhancer in ageing-related cognitive decline.

Synthetic pyridoindole-type substances derived from the lead compound stobadine represent promising agents in treatment of a range of pathologies including neurological disorders. The beneficial biological effects were suggested to be likely associated with their capacity to ameliorate oxidative damage. In our study, the effect of supplementation with the derivative of stobadine, SMe1EC2, on ageing-related cognitive decline in rats was investigated. The 20-months-old male Wistar rats were administered SMe1EC2 at a low dose, 0.5 mg/kg, daily during eight weeks. Morris water maze test was performed to assess the spatial memory performances. The cell-based assays of capacity of SMe1EC2 to modulate proinflammatory generation of oxidants by microglia were also performed. The rats treated with SMe1EC2 showed significantly increased path efficiency, significantly shorter time interval of successful trials and exerted also notably lower frequencies of clockwise rotations in the pool compared to non-supplemented aged animals. Mildly improved parameters included test durations, distances to reach the platform, time in periphery of the pool and overall rotations in the water maze. However, the pyridoindole SMe1EC2 did not show profound inhibitory effect on production of nitric oxide and superoxide by activated microglial cells. In conclusion, our study suggests that pyridoindole SMe1EC2, at low doses administered chronically, can act as cognition enhancing agent in aged rats. The protective mechanism less likely involves direct modulation of proinflammatory and prooxidant state of microglia, the prominent mediators of neurotoxicity in brain ageing and neurodegeneration.

In Vitro Metabolomic Approach to Hippocampal Neurodegeneration Induced by Trimethyltin.

Search for indicators of neurodegenerative disorders is a hot topic where much research remains to be done. Our aim was to determine proton nuclear magnetic resonance ((1)H-NMR) spectra of brain metabolites in the trimethyltin (TMT) model of neurodegeneration. Male Wistar rats were subjected to TMT or saline and were sacrificed on day 3 or 24 after administration. (1)H-NMR spectrum was measured on the 600 MHz Varian VNMRS spectrometer in nano-probe in the volume of 40 µl of hippocampal extracts. TMT administration resulted in reduction of the hippocampal weight on day 24. Of the sixteen identified metabolite spectra, decreased aspartate and increased glutamine contents were observed in the initial asymptomatic stage of neurodegeneration on day 3 in hippocampal extracts of TMT exposed rats compared to sham animals. Increased myo-inositol content was observed on day 24. The presented data provide further knowledge about this experimental model and putative indicators of neuronal damage.

Progressive increase of lysosomal enzyme activities in hippocampus associated with reduction of population spike in a rat model of neurodegeneration.

OBJECTIVES: Extensive effort has been made to identify early markers of neurodegeneration as late stages have no chance of treatment. Recently, many experimental models have been used to study hallmarks of neuronal injury. One of them is the model of trimethyltin (TMT)-induced damage associated with cognitive decline, thus called a model of Alzheimer-like disease. OBJECTIVE AND METHODS: Our aim was to study neuronal transmission in hippocampal slices of male Wistar rats affected with a single dose of TMT (7.5 mg/kg, i.p.) during the first three weeks of its action. The monitored time periods after TMT administration were days 1-3; 8-10 and 15-17. At the same time periods, right hippocampi were collected for determination of changes in specific activities of two lysosomal enzymes. Electrophysiological measurements were based on stimulation of Schäffer collaterals and registration of evoked responses in the stratum pyramidale and the stratum radiatum at the CA3-CA1 synapse. Specific activities of N-acetyl-ß-D-glucosaminidase (NAGA) and cathepsin D (Cat D) were determined spectrophotometrically. RESULTS: During three weeks after i.p. TMT administration to rats, we found a time-dependent reduction of postsynaptic neuronal firing, expressed by diminished population spike (PoS) amplitude recorded in the stratum pyramidale accompanied with marked increase in specific activity of NAGA to respective 111%, 163% and 252% in the 1st, 2nd and 3rd week compared to unaffected rats. In the stratum radiatum, reduction of the slope of excitatory postsynaptic potential was not time-dependent but almost constantly reduced from the 1st to 3rd week after TMT administration (55-60%) compared to control rats. Specific activity of lysosomal enzyme Cat D was significantly increased in the 3rd week after TMT administration. CONCLUSION: This work demonstrates a time-dependent reduction of somatic response in the hippocampus of TMT affected rats during the first three weeks. This reduction of neuronal firing was later accompanied with increase of specific activity of NAGA and Cat D, supporting evidence that lysosomal dysfunction may be one of the primary contributors to TMT-induced neurodegeneration.

Pyridoindole antioxidant-induced preservation of rat hippocampal pyramidal cell number linked with reduction of oxidative stress yet without influence on cognitive deterioration in Alzheimer-like neurodegeneration.

BACKGROUND: The idea of antioxidant therapy attenuating Alzheimer disease (AD) neuropathology starts to be attractive. Animal models are often used in these studies. An AD-like model of trimethyltin (TMT)-induced neurodegeneration, targeting the hippocampus, involves neuronal cell death and cognitive impairment. OBJECTIVES: Effect of the pyridoindole SMe1EC2 (3×50 mg/kg) and vitamin C (3×50mg/kg) was analyzed in the model of TMT-induced (8 mg/kg) neurodegeneration. METHODS: The study was focused on the effect of the antioxidants tested on learning performance in the Morris water maze (MWM) on days 21-25 after TMT administration, on biochemical variables - malondyaldehyde (MDA) and lysosomal enzyme NAGA in brain cortex and blood serum, and on pyramidal cell number in the CA1 area of the hippocampus on day 31 after TMT administration in adult male Wistar rats (n=32). RESULTS: Critical deterioration of learning performance was observed due to the TMT administration in the MWM. Further, apparent reduction of pyramidal cell number to 21% in the CA1 area of the hippocampus, increased MDA and NAGA activity in serum and increased NAGA activity in the cortex were determined contrary to controls. In serum, an increase of MDA level was prevented by both antioxidants tested without any effect on NAGA activity. SMe1EC2 apparently preserved pyramidal cell viability in the CA1 area. Both substances tested failed to ameliorate the detrimental effect of TMT on spatial memory. CONCLUSION: The biochemical and morphometrical findings suggest that reduction of oxidative stress may play a role in AD-like neurodegeneration. Different doses and timing of SMe1EC2 administration might bring improvement in next learning performance.

Effect of antioxidants on functional recovery after in vitro-induced ischemia and long-term potentiation recorded in the pyramidal layer of the CA1 area of rat hippocampus.

Ischemic stroke is one of the leading causes of cognitive impairment. Antioxidants may be beneficial in brain diseases in which oxidative stress can be assumed. The effect of two antioxidants, stobadine and its new derivative coded SMe1EC2, was studied on post-ischemic functional recovery in the hippocampus of young and 18-month-old rats. The synaptic transmission was apparently absent after 6-min hypoxia/hypoglycemia in both age groups. Re-oxygenation resulted in negligible functional recovery in untreated slices, yet the presence of pyridoindoles tested elicited improved recovery upon re-oxygenation. SMe1EC2 was found more effective in post-ischemic functional recovery and was further tested in the hippocampus of 15-month-old rats in long-term potentiation (LTP) experiments, a synaptic model of learning and memory mechanisms. In slices of aged rats, 3.5-min hypoxia/hypoglycemia resulted in depression of the LTP induction phase (immediately after high frequency stimulation) and this was prevented in the presence of SMe1EC2 (3 µmol/l). Upon "normoxia", marked amelioration of LTP was recorded in the presence of the antioxidant in about 1.5 order lower concentration. These results suggest a possible application of the pyridoindole in the management of brain ischemia and cognitive impairment.

Early and late stage of neurodegeneration induced by trimethyltin in hippocampus and cortex of male Wistar rats.

BACKGROUND: Trimethyltin (TMT), a potent neurotoxicant, elicits neuronal death in the limbic system and causes damage particularly in the hippocampus. Current interest relates to the opportunity to use TMT as an experimental model of neurodegeneration in the study of Alzheimer-like diseases. OBJECTIVE: In light of recently found species-specific and strain-specific differences in TMT intoxication, the aim of this study was to characterise the model of TMT-induced neurodegeneration in the brain of Wistar rats during early (days 1-3) and late (days 22-24) stage of neuronal damage. RESULTS: Reduced neurotransmission at the CA3-CA1 synapse and reduced number of cells accompanied with reduced width of CA1 pyramidal cell layer were observed at the late stage of TMT intoxication (7 mg/kg, i.p.). Long-term potentiation of excitatory postsynaptic potential, elicited by train stimulation (100 Hz, 1s), was not impaired by the dose of TMT tested. Activation of pro-apoptotic caspase-3 suggests involvement of apoptosis in neuronal cell death in the hippocampus at the late stage of TMT intoxication. Increased protein carbonyl formation was proved in the cortex at the early stage of TMT intoxication compared both to controls in the early and late stage and to the late stage of TMT action. CONCLUSIONS: TMT-induced neurodegeneration was proved in the brain of Wistar rats. Changes found in the parameters examined may be reliable indicators of neurodegeneration. The increased level of carbonyls in the cortex at the early stage indicates that particularly at the onset of progressive neurodegeneration compounds with antioxidative properties may be effective in slowing down brain injury.

The new pyridoindole antioxidant SMe1EC2 and its intervention in hypoxia/hypoglycemia-induced impairment of longterm potentiation in rat hippocampus.

Previously, the pyridoindole SMe1EC2 was proved to inhibit lipoperoxidation and carbonylation of proteins in rat brain cortex in the system Fe(2+)/ascorbate and improvement of resistance of the rat hippocampus was reported against ischemic conditions in vitro (hypoxia/hypoglycemia) expressed by the enhanced neuronal response recovery in reoxygenation. The hippocampus fulfils many of the criteria for a neuronal correlate of learning and memory. Recently, an impairment of hippocampal long-term potentiation (LTP) was reported under oxidative stress. Different therapies, including antioxidants, have been studied intensively concerning the impairment of neuronal plasticity. In this study marked reduction of LTP, elicited by a single burst (100 Hz, 1s) in the CA3-CA1 area of rat hippocampal slices, was shown due to transient hypoxia/hypoglycemia compared to control slices. On the basis of previously reported antioxidant and neuroprotective effects of SMe1EC2, its effect on loss of LTP in the hippocampus due to ischemic conditions was studied in vitro. The pyridoindole tested improved hypoxia/hypoglycemia-induced reduction of LTP compared to untreated hypoxic slices. An opposite effect of SMe1EC2 on LTP induction was found in control slices. The mechanism of SMe1EC2 action on LTP in ischemic conditions has been suggested to differ from the mechanism of its effect in "normoxia" and may be due to different redox status in control and ischemic brain tissue. The manifested LTP-protective effect of SMe1EC2 observed in the rat hippocampus exposed to ischemia in vitro may find exploitation in therapy associated with injured neuronal plasticity in some conditions, including ischemia, trauma and aging in man.

Maternal treatment of rats with the new pyridoindole antioxidant during pregnacy and lactation resulting in improved offspring hippocampal resistance to ischemia in vitro.

OBJECTIVE: Damage to the developing brain may be caused by maternal environment, nutritional deficiencies, failure of protective mechanisms, etc. Further, the developing brain may be damaged by intrauterine ischemia or by ischemia in newborns complicated by perinatal asphyxia. There is an effort to find agents with neuroprotective effect on the developing brain. The aim was to study the effect of the new pyridoindole antioxidant SMe1EC2 on the resistance of offspring hippocampus exposed to ischemia in vitro after treatment of mothers. MATERIALS AND METHODS: The electrically evoked responses were determined by extracellular recording from offspring hippocampal slices. The effect of oral treatment of rats with SMe1EC2 over 18 consecutive days, from day 15 of gestation to day 10 post partum (PP) was analyzed in the model of ischemia in vitro measured on the hippocampus of 21-day-old pups, with focus on neuronal function recovery in reoxygenation. RESULTS: Increased recovery of neuronal response was found at the end of 20-min reoxygenation in offspring hippocampal slices exposed to 10-min hypoxia/hypoglycemia from rats whose mothers were treated with the dose of 50 and 250 mg/kg of SMe1EC2, compared to control offspring slices (mothers received vehicle over the same time). CONCLUSIONS: The increased offspring hippocampus resistance to hypoxia/hypoglycemia due to 18-day maternal treatment with SMe1EC2 might have been obtained via the transplacental way as well as in the neonatal period via breast milk, skin and saliva. The manifested neuroprotective effect of SMe1EC2 on the developing brain might find exploitation during risk pregnancy and delivery.

Oxidative stress induced by the Fe/ascorbic acid system or model ischemia in vitro: effect of carvedilol and pyridoindole antioxidant SMe1EC2 in young and adult rat brain tissue.

New effective strategies and new highly effective neuroprotective agents are being searched for the therapy of human stroke and cerebral ischemia. The compound SMe1EC2 is a new derivative of stobadine, with enhanced antioxidant properties compared to the maternal drug. Carvedilol, a non-selective beta-blocker, possesses besides its cardioprotective and vasculoprotective properties also an antioxidant effect. We compared the effect of carvedilol and SMe1EC2, antioxidants with a similar chemical structure, in two experimental models of oxidative stress in young and adult rat brain tissue. SMe1EC2 was found to improve the resistance of hippocampal neurons to ischemia in vitro in young and even in 18-month-old rats and inhibited formation of protein carbonyl groups induced by the Fe(2+)/ascorbic acid pro-oxidative system in brain cortex homogenates of young rats. Carvedilol exerted a protective effect only in the hippocampus of 2-month-old rats and that at the concentration 10-times higher than did SMe1EC2. The inhibitory effect of carvedilol on protein carbonyl formation induced by the pro-oxidative system was not proved in the cortex of either young or adult rats. An increased baseline level of the content of protein carbonyl groups in the adult versus young rat brain cortex confirmed age-related changes in neuronal tissue and may be due to increased production of reactive oxygen species and low antioxidant defense mechanisms in the adult rat brain. The results revealed the new pyridoindole SMe1EC2 to be more effective than carvedilol in neuroprotection of rat brain tissue in both experimental models involving oxidative stress.

Effect of the new pyridoindole antioxidant SMe1EC2 on functional deficits and oedema formation in rat hippocampus exposed to ischaemia in vitro.

OBJECTIVES: The idea of neuroprotective therapy for ischaemic stroke is based on results from studies on experimental animal models of brain ischaemia demonstrating efficacy of many natural and synthetic agents. Contrary to positive conclusions with antioxidants from animal models, clinical experience failed to find neuroprotectants so efficient in human stroke, infarction, brain trauma, tissue preservation, etc. Thus new highly effective neuroprotective agents need to be discovered. METHODS: Effects of 10-day oral treatment with the new pyridoindole derivative, code SMe1EC2, was analysed in the model of ischaemia in vitro measured five days after oral treatment, with focus on neuronal function recovery. The responses were determined by extracellular recording from rat hippocampal slices. Further, effect of SMe1EC2, applied into the incubation medium before and during ischaemia in vitro, was studied on the oedema extent in neurons of the CA1 area. RESULTS: Ten-day oral treatment of rats with SMe1EC2 at the doses 50 or 250 mg/kg resulted in improved resistance of hippocampal neurons to 6.5-min hypoxia/hypoglycaemia in vitro measured during reoxygenation, compared to untreated rats. Application of the drug tested into the incubation medium 30 min before and during 6-min hypoxia/hypoglycaemia resulted in reduction of oedema formation in the CA1 area compared to untreated slices exposed to ischaemia in vitro. CONCLUSION: The current study confirmed the neuroprotective effect of the pyridoindole antioxidant SMe1EC2 on the level of recovery of neuronal function as well as on affection of morphological changes expressed by reduced oedema extent in the rat hippocampus under ischemic conditions in vitro.

Effect of transient ischemia on long-term potentiation of synaptic transmission in rat hippocampal slices.

OBJECTIVES: Long-term potentiation (LTP) of neuronal activity in the hippocampus is thought to be a substrate for learning and memory. The influence of ischemia (IS) (hypoxia/hypoglycemia) on induction of LTP of synaptic transmission (ST) by high frequency stimulation (HFS) was investigated in rat hippocampal slices. METHODS: Neurons were stimulated via Schäffer collaterals and field excitatory postsynaptic potentials (fEPSP) were recorded extracellularly from the CA1 region. LTP was induced by one single train (100 Hz, 1s). RESULTS: In controls LTP of ST after HFS was 179.70+/-12.53%. Short IS of 2.5-4.5 min elicited a transient failure of ST, with return to former value followed by further increase of fEPSP amplitude to 142.28+/-16.24%, compared to amplitude before IS. HFS was elicited 40 min after exposure to IS and LTP was measured over further 40-60 min. LTP in slices exposed to 2.5-4.5-min IS was 139.94+/-14.01%. IS of 6-7.5 min elicited a prolonged failure of ST, with almost full recovery (96.69+/-14.42%). LTP was not activated 40 min after 6-7.5-min IS and the amplitude of fEPSP was even reduced to 80.14+/-19.19% compared to the former mean value of fEPSP 10 min before HFS. CONCLUSION: The results revealed that prolonged 6-7.5-min IS influenced induction of LTP of ST in the hippocampus and thus it could have deleterious effects on learning and memory. These findings may have clinical implications in stroke, brain ischemia, sleep apnoe and call for studying the effect of neuroprotectants on the induction of LTP in hippocampus exposed to oxidative stress.

Effect of the pyridoindole SMe1EC2 and compounds affecting A(1) and A(2A) adenosine receptors in rat hippocampus under ischemia in vitro.

The effect of the newly synthesized pyridoindole antioxidant SMe1EC2 (1 micromol/l) and drugs activating or inhibiting adenosine receptors was tested under ischemia. Synaptic transmission was recorded extracellularly before and under 6-min ischemia and 20-min reoxygenation in rat hippocampal slices in vitro. In untreated slices, ischemia elicited failure of synaptic transmission and excitability expressed by a population spike decay (t(0.5) = 1.7 +/- 0.1 min) and poor recovery of synaptic transmission at the end of reoxygenation, expressed as percentage of PoS amplitude of that at zero minute of ischemia (9.9 +/- 3.6%). The compound SMe1EC2 increased recovery of PoS amplitude in reoxygenation (31.2 +/- 7.0% of that at the beginning of ischemia) and decreased the number of irreversibly damaged slices in reoxygenation (64%) compared to untreated slices (80%). Co-administration of SMe1EC2 + SCH-58261 (1 micromol/l, A(2A) adenosine receptor antagonist) resulted in delayed synaptic transmission decay during 6-min ischemia (t(0.5) = 2.3 +/- 0.1 min), increased PoS amplitude recovery during reoxygenation (37.7 +/- 12.4% of that at zero minute of ischemia), and in a decreased number of slices with damaged synaptic transmission at the end of reoxygenation (54%), all data compared to untreated controls. Co-administration of pyridoindole with CGS 21680 (1 micromol/l, A(2A) adenosine receptor agonist) or with DPCPX (100 nmol/l, A(1) adenosine receptor antagonist) eliminated the described effect. Further studies are required to elucidate the putative influence of manipulation with adenosine receptors on the neuroprotective effect of SMe1EC2 under ischemia.