Determination of Bioactive Compound Kynurenic Acid in Linum usitatissimum L

Kynurenic acid (KYNA) is a bioactive compound exhibiting multiple actions and positive effects on human health due to its antioxidant, anti-inflammatory and neuroprotective properties. KYNA has been found to have a beneficial effect on wound healing and the prevention of scarring. Despite notable progress in the research focused on KYNA observed during the last 10 years, KYNA's presence in flax (Linum usitatissimum L.) has not been proven to date. In the present study, parts of flax plants were analysed for KYNA synthesis. Moreover, eight different cultivars of flax seeds were tested for the presence of KYNA, resulting in a maximum of 0.432 µg/g FW in the seeds of the cultivar Jan. The level of KYNA was also tested in the stems and roots of two selected flax cultivars: an oily cultivar (Linola) and a fibrous cultivar (Nike). The exposure of plants to the KYNA precursors tryptophan and kynurenine resulted in higher levels of KYNA accumulation in flax shoots and roots. Thus, the obtained results indicate that KYNA might be synthesized in flax. The highest amount of KYNA (295.9 µg/g dry weight [DW]) was detected in flax roots derived from plants grown in tissue cultures supplemented with tryptophan. A spectroscopic analysis of KYNA was performed using the FTIR/ATR method. It was found that, in tested samples, the characteristic KYNA vibration bands overlap with the bands corresponding to the vibrations of biopolymers (especially pectin and cellulose) present in flax plants and fibres.

P0016EFFECT OF GEMFIBROZIL ON KYNURENINE AMINOTRANSFERASE ACTIVITY AND KYNURENIC ACID PRODUCTION IN RAT KIDNEY

Background and Aims

Hypertriglyceridemia is the most common lipid disorder in chronic kidney disease. Lifestyle changes and fibrates administration are main methods of lowering triglycerides’ level. PPARα (peroxisome proliferator-activated receptor-α) activation is the primary mechanism of action of fibrates.

A tryptophan metabolite, kynurenic acid (KYNA), is produced from L-kynurenine (L-KYN) by kynurenine aminotransferases (KATs). KAT I and KAT II isoenzymes are the best analyzed KATs. KYNA acts predominantly as a nonselective antagonist of ionotropic glutamatergic receptors, particularly N-methyl-D-aspartate (NMDA) type, which are highly expressed in the kidney. Natriuretic and hypotensive effects of KYNA are well described. Diet rich in fatty acids was reported to elevate central and peripheral KYNA level.

The goal of presented study was to analyze the influence of gemfibrozil, one of the fibrates given to treat hypertriglyceridemia, on KYNA production and the activity of KAT isoenzymes: KAT I and KAT II, in rat kidney in vitro. Additionally, the molecular docking of gemfibrozil to KAT I and KAT II structures was performed to study drug-enzyme interaction. On the final step the microarray datamining was carried out to investigate whether gemfibrozil affects the expression of KAT-coding genes.

Method

The effect of gemfibrozil on KYNA synthesis together with KAT I and KAT II activity was tested in rat kidney homogenates in vitro after 2 hours incubation in the presence of L-KYN and gemfibrozil. The drug was examined at the concentration of 1 µM, 10 µM, 50 µM, 100 µM, 500 µM and 1 mM. Production of KYNA was analyzed using the high performance liquid chromatography (HPLC) with fluorometric detector.

Results

Gemfibrozil at 100 µM, 500 µM and 1 mM decreased KYNA production in kidney homogenates in vitro to 66% (P < 0.05), 58% (P < 0.01) and 41% (P < 0.01) of control value, respectively. At 100 µM, 500 µM and 1 mM concentration gemfibrozil lowered renal KAT I activity in vitro to 68% (P < 0.05), 56% (P < 0.01) and 52% (P < 0.01) of control value, respectively. Moreover, gemfibrozil at 500 µM and 1 mM concentration decreased kidney KAT II activity in vitro to 47% (P < 0.001) and 26% (P < 0.001) of control value, respectively. Results of the molecular docking suggested that gemfibrozil may affect the active site of both KAT I and KAT II. Publicly available microarray datasets suggested that the expression of KAT-coding genes does not change after gemfibrozil administration.

Conclusion

Gemfibrozil decreases KYNA production in rat kidney in vitro through inhibition of KAT I and KAT II isoenzymes. Presented results indicate a novel mechanism of gemfibrozil’s action in the kidney. Its potential role in nephrotoxicity needs verification in upcoming studies.

Effect of Kynurenic Acid on Pupae Viability of Drosophila melanogaster cinnabar and cardinal Eye Color Mutants with Altered Tryptophan-Kynurenine Metabolism

Kynurenic acid (KYNA) is one of the metabolites of evolutionary conserved tryptophan (Trp)/kynurenine (Kyn) metabolic pathway. Elevation of KYNA contributes to development of psychosis in schizophrenia but attenuates neurodegeneration in Drosophila model of Huntington's disease. We have reported that KYNA increased lethality of pupae of wild-type flies, but not of vermilion (v) mutants with impaired formation of Kyn from Trp, suggesting that KYNA toxicity depends on its interaction with downstream Kyn metabolites [i.e., 3-hydroxykynurenine (3-HK) and/or xanthurenic acid (XA)]. The present study aimed to further explore the mechanisms of KYNA-induced lethality by the assessment of KYNA effect on pupae of two Drosophila mutants: cinnabar (cn), characterized by higher KYNA and lower 3-HK production, and cardinal (cd), characterized by higher 3-HK and XA levels compared to wild-type flies. Our microarray datamining revealed that the gene expression pattern of enzymes forming Trp/Kyn pathway stands in line with previously reported developmental changes in KYNA, 3-HK, and XA concentrations in wild-type and mutant flies. Administration of KYNA increased pupae lethality in cd, but not in cn mutants. Present data suggest that toxic effect of exogenous KYNA depends on the presence of 3-HK and/or XA. This is further supported by our finding that early stages of Drosophila development are associated with a positive expression pattern of genes encoding sulfotransferases, enzymes that are inhibited by KYNA and are involved in detoxification of XA. Alternatively, the toxic effect of KYNA might depend on anti-proliferative effects of KYNA.

Quinaldic acid in synovial fluid of patients with rheumatoid arthritis and osteoarthritis and its effect on synoviocytes in vitro

BACKGROUND

Previously, we have demonstrated that kynurenic acid (KYNA), an endogenous metabolite of tryptophan formed along kynurenine pathway, is present in synovial fluid of rheumatoid arthritis (RA) and osteoarthritis (OA) patients. In this study, the goal was to investigate the presence of quinaldic acid (QUDA), a putative metabolite of KYNA, in synovial fluid of RA and OA patients.

METHODS

The effect of QUDA on proliferation and motility of synovial fibroblasts and its interaction with KYNA were determined in vitro. The study was conducted on synovial fluid obtained from 38 patients with RA and 15 patients with OA. QUDA was identified and quantified using the gas chromatography-mass spectrometry (GC-MS) method. In vitro experiments were conducted on rabbit synoviocyte cell line HIG-82.

RESULTS

Presence of QUDA was detected in all 53 samples of synovial fluid. The concentration of QUDA in synovial fluid obtained from patients with RA was 28.6 ± 14.9 pmol/ml, which was lower in comparison with OA 42.3 ± 10.0 pmol/ml. QUDA content positively correlated with the number of tender joints and negatively with the total cell counts determined in synovial fluid of RA patients. It did not correlate with KYNA content. QUDA reduced both proliferation and motility of synoviocytes in a dose-dependent manner. The enhancement of antiproliferative action of QUDA by KYNA was evidenced.

CONCLUSIONS

Data show a local deficit of QUDA in RA patients and suggest its potential role as an endogenous substance controlling synoviocyte viability.

[Kynurenic acid--a new tool in the treatment of hiperhomocysteinemia and its consequences?]

Atherosclerosis together with its cardiovascular consequences is the most common and significant cause of death, particularly in highly developed countries. The process of atherogenesis begins as soon as in childhood and depends on classical risk factors. Atherosclerosis also results from a chronic inflammatory-immune process which takes place in the vascular walls. Furthermore, it has been known for a number of years that the development of atherosclerotic lesions is closely connected with the concentration of homocysteine in serum. Homocysteine is a sulfur amino acid originating from methionine. An increased concentration of homocysteine in blood harmfully influences blood vessels, leading to a higher risk of ischemic heart disease and stroke. Since tackling classical atherosclerosis risk factors is not efficient enough when it comes to protecting the cardiovascular system from diseases, new substances possessing anti-atherogenic properties, especially endogenous ones, are sought. Recently, researchers have paid attention to a connection between homocysteine and an endogenous tryptophan derivative, kynurenic acid. Recently, it was revealed that kynurenic acid counteracts the harmful effects of homocysteine on endothelium cells in vitro. The hypothesis assuming homocysteine-kynurenate interplay suggests the existence of a new mechanism of atherogenesis and gives us an opportunity to use this knowledge in both prevention and treatment of cardiovascular diseases.

Presence of L-kynurenine aminotransferase III in retinal ganglion cells and corpora amylacea in the human retina and optic nerve

BACKGROUND

Corpora amylacea (CAm) are a hallmark of aging and neurodegeneration. The presence of kynurenine aminotransferases I and II (KAT I and II) in CAm in the human retina and optic nerve has been already shown. The present study aimed to examine kynurenine aminotransferase III (KAT III) immunoreactivity in CAm in the human retina and optic nerve.

MATERIAL AND METHODS

Polyclonal antibody against KAT III was used on sections of human eyes enucleated due to malignant uveal melanoma. PAS-stained sections of CAm were compared with KAT III stained ones.

RESULTS

KAT III immunoreactivity was observed in CAm in the retina, prelaminar, laminar and retrolaminar region of the optic nerve with similar location to PAS-stained sections. The most intense staining was observed in the retrolaminar part of the optic nerve. KAT III immunoreactivity was also present in the cytoplasm of retinal ganglion cells.

CONCLUSIONS

Expression of KAT III in CAm in the human retina and optic nerve indicates that this enzyme may be relevant in mechanisms of neurodegeneration leading to CAm formation.

Kynurenic acid, an endogenous constituent of rheumatoid arthritis synovial fluid, inhibits proliferation of synoviocytes in vitro

Kynurenic acid is an antagonist of ionotropic glutamate receptors. It has been found that glutamate antagonists inhibit proliferation of different human tumor cells. Since the hyperplasia of synovial fibroblasts is one of the most striking features of inflammatory arthritis, the main goals of this study were detection and quantification of kynurenic acid in synovial fluid obtained from patients with rheumatoid arthritis, and determination of its effect on proliferation of synoviocytes in vitro. Presence of kynurenic acid was determined by HPLC in all 58 samples of synovial fluid. The mean concentration was 15.89 pmol/ml. Kynurenic acid inhibited synoviocyte proliferation with the IC50 value of 5.9 mM. In subthreshold concentration of 0.3 mM it enhanced antiproliferative action of celecoxib and nimesulide. In conclusion, the presence of kynurenic acid in synovial fluid was documented in patients with rheumatoid arthritis. Its potential role as an endogenous substance, controlling synoviocyte proliferation can be suggested.

Nicotine diminishes anticonvulsant activity of antiepileptic drugs in mice

Nicotine administered acutely at subconvulsive dose of 4 mg/kg, significantly decreased the protective activity of valproate, carbamazepine, diphenylhydantoin, phenobarbital, topiramate and lamotrigine against maximal electroshock-induced tonic convulsions in mice. The obtained data may suggest that interaction between nicotine and antiepileptic drugs should be carefully considered as a cause of the therapeutic failure in epileptic patients.

Deficit of endogenous kynurenic acid in the frontal cortex of rats with a genetic form of absence epilepsy

The present studies sought to determine the concentrations of endogenous kynurenic acid (KYNA) and to measure the activity of kynurenine aminotransferases (KAT) I and II in the discrete brain regions of 3- and 6-month old WAG/Rij rats, a genetic model of absence epilepsy. Analogues experiments were performed using age-matched ACI rats, which served as a non-epileptic control. The age-dependent increase in KYNA concentration in the frontal cortex of WAG/Rij rats was considerably reduced in comparison to what was found in ACI rats. Consequently, the concentration of KYNA in the frontal cortex of epileptic rats was significantly lower than in non-epileptic controls. There were no such strain differences in other brain regions. The activities of KAT I and II also showed age-dependent increase with an exception for KAT II in the frontal cortex. Our data suggest that selective deficits of endogenous KYNA may account for increased excitability in the frontal cortex, which in turn may lead to the development of spontaneous spike-wave discharges in WAG/Rij rats.

The use of the radioisotope method in studies of pesticide penetration into the eyeball

The studies concerning the effects of pesticides on the human body focused mainly on their local action or chronic poisoning of the organism. In this study we examine the pesticide penetration into the eyeball resulting from direct contact with the eye. We used an isotope-labelled carbamate pesticide -- carbaryl. The determinations of the amount and concentration of this substance in the cornea, aqueous humour, vitreous humour and retina were performed using the method measuring beta radiation emitted by radioactive carbon. The results revealed measurable concentrations of labelled carbamate in the cornea and aqueous humour 10 and 30 min after application. The levels of this pesticide in the vitreous humour and retina were very low and difficult to analyse statistically. The described method appears to be useful in determining the range and rate of eye penetration by environmental toxins having direct contact with the eyeball.

Amino acid derivatives with anticonvulsant activity

A series of benzylamides of N-alkylated, N-acylated or free nine cyclic and one linear amino acids as potential anticonvulsants have been synthesized. The structures of the obtained compounds were designed on the basis of the previously determined structure and physicochemical properties/anticvonvulsant activity relationship of the formerly synthesized compounds of this type. The obtained compounds were evaluated in mice after intraperitoneal (i.p.) administration, by maximal electroshock seizure test (MES test), subcutaneous (s.c.) pentylenetetrazol test (s.c. PTZ test) and by the rotarod neurotoxicity test (Tox test). The results were the basis for their classification into one of three classes of the Anticonvulsant Screening Project (ASP) of the Antiepileptic Drug Development Program (ADDP) of the NIH. Three selected compounds were tested quantitatively in rats after oral administration. The MES ED50, s.c. PTZ ED50, Tox TD50 were determined and their protective index (PI) values were calculated. Anticonvulsant activity of the most promising compound (15) was examined in different seizure models. The respective ED50 and PI values of this compound were as follows: against bicuculline, 73 and 1.4; against PTZ, 47 and 2.2; against strychnine, 73 and 1.4; against pilocarpine 156, and 0.7; against kainic acid (2-carboxy-4-isopropenyl-3-pyrrolidineacetic acid), 39 and 2.6; against AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid), 10 and 10.3 and against NMDA (N-methyl-D-Aspartic acid), 114 and 0.9.

Organochlorine pesticides concentration in the drinking water from regions of extensive agriculture in Poland

Considerable amounts of organochlorine pesticides (DDT, lindane, heptachlor and methoxychlor) were detected in drinking water samples during a two-year study in Warka-Grojec rural region of Poland. The average incidence of drinking water sources with detectable levels of pesticides ranged from 20 to 30%. According to Polish regulations concerning water quality, individual concentrations did not reach the maximum admissible level. However, the levels of pesticides in most cases exceeded the maximum admissible concentrations recommended by the European Union

Age dependency of the susceptibility of rats to aminooxyacetic acid seizures

Immature rats are more susceptible to clonic seizures induced by aminooxyacetic acid (AOAA) than mature and senile rats. Highest susceptibility to AOAA seizures was observed in 7-14-day-old rat pups. The lowest susceptibility was recorded in 10-20 month-old rats. AOAA seizures in 14-day-old rats were blocked by clonazepam and valproate, but not by phenobarbital, carbamazepine, diphenylhydantoin, trimethadione or ethosuximide. Morphological analysis of brains from 14-day- and 3-month-old rats which experienced AOAA seizures did not reveal epilepsy-related damage. These observations suggest that immature rat brain is highly prone to convulsions induced by AOAA and that such convulsions are difficult to control by available antiepileptic treatment.

[24-hour fluctuations of the values of certain components of the saliva and dental plaque in school children]

24-hours changes were studied in the saliva and dental plaque of the concentrations of total fluorine, inorganic phosphate and protein, and of pH value. The study was carried out in two groups of school children: I--control, II--subjected to contact fluoridation. The obtained results showed that circadian changes occurred in controls and in children subjected to fluoridation.

Substantia nigra and motor control in the rat: effect of intranigral alpha-kainate and gamma-D-glutamylaminomethylsulphonate on motility

Bilateral microinjections of an excitatory amino acid, alpha-kainate (KA), 5-50 ng, into the substantia nigra pars reticulata (SNR) result in an increase in the muscle tone and catalepsy in rats. The preferential KA/quisqualate antagonist, gamma-D-glutamylaminomethylsulphonate (gamma-D-GAMS), 10 micrograms, blocks the actions of KA, 25 ng, when coadministered into the SNR. The chemical lesion of the caudate-putamen with 6-hydroxydopamine (6-OHDA) does not affect either increases in the muscle tone or catalepsy produced by KA, 25 ng, from the SNR. The lesion of the caudate-putamen with ibotenate moderately enhances the effect of KA, 25 ng, on the muscle tone. Microinjections of KA, 25 ng, into the substantia nigra pars compacta (SNC) do not increase the muscle tone and lead to significantly less pronounced catalepsy relative to that observed following the injections of KA into the SNR. Unilateral microinjections of KA, 10-50 ng, into the SNR elicit ipsilateral turning in rats in a dose- and time-dependent manner. Unilateral application of gamma-D-GAMS, 1-10 micrograms, into the SNR produces contralateral turning. The turning evoked by KA, 25 ng, or gamma-D-GAMS, 10 micrograms, is affected neither by 6-OHDA nor by ibotenate lesion of the caudate-putamen. These results demonstrate that excitatory neurotransmission in the substantia nigra participates in the regulation of the muscle tone and posture in rats.

Effect of aminophylline on the protective action of common antiepileptic drugs against electroconvulsions in mice

The increasing amount of data tends to suggest that adenosine-mediated inhibition may play a role in the anticonvulsant activity of a number of antiepileptic drugs. Consequently, we tried to reverse the protective action of acetazolamide [(40 and 80 mg/kg) i.p.; 60 min before the test]; carbamazepine (20 and 30 mg/kg i.p., 60 min); diazepam (5 and 10 mg/kg i.p., 60 min); diphenylhydantoin (8 and 12 mg/kg i.p., 120 min), phenobarbital (20 and 30 mg/kg i.p., 120 min) and valproate (200 and 300 mg/kg i.p., 30 min) with aminophylline (50 and 100 mg/kg i.p., 30 min) against electroconvulsions in mice. Aminophylline markedly decreased the anticonvulsant efficacy of almost all drugs studied, acetazolamide (40 and 80 mg/kg) and carbamazepine (30 mg/kg) being the only exceptions. The ethylenediamine component of aminophylline did not modify the anticonvulsant activity at all. These results seem to support the suggestion that aminophylline-induced blockade of adenosine receptors might be involved in the reversal of the protective action of at least some drugs studied. Regardless of the nature of the aminophylline-induced impairment in the anticonvulsant efficacy of a number of antiepileptic drugs, the use of methylxanthines in epileptic patients for the treatment of obstructive lung diseases should be avoided.

The involvement of catecholaminergic mechanisms in the appearance of wet dog shakes produced by carbachol chloride in rats

Noradrenaline (NA), methoxamine, dopamine (DA), given intracerebroventricularly (ICV), and L-DOPA, administered systemically, significantly blocked wet dog shakes (WDS) produced by carbachol chloride (10 microgram/10 microliter, ICV) in rats. Reserpine, alpha-methyl-p-tyrosine and FLA 63 did not affect WDS, while diethyldithiocarbamic acid depressed it. Aceperone and yohimbine weakened shaking response to carbachol but phentolamine given ICV showed no effect on WDS. Propranolol and isoproterenol administered ICV did not significantly influence WDS. Apomorphine failed to affect WDS induced by carbachol. Pimozide and spiperone were also ineffective against WDS, but amphetamine and metoclopramide efficiently blocked it. Selective depletion of brain NA concentration considerably enhanced WDS, while selective depletion of brain DA concentration failed to affect it. These results suggest that carbachol-induced WDS behavior is under the inhibitory control of noradrenergic neurons.

Effect of glutamic acid diethylester on (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid and kainic acid-induced changes of body temperature in rats

A low dose (1 microgram) of intracerebroventricularly injected (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) produced a hyperthermic response in rats, while a high dose of AMPA (2.5 micrograms), similarly to kainic acid (0.1 microgram) produced a biphasic effect: short-lasting hypothermia followed by hyperthermia. These effects on body temperature were not affected by pretreatment with 200 mg/kg ip of glutamic acid diethylester (GDEE), which by itself, produced a significant hypothermia. The results indicate that the effects of kainic acid and AMPA on body temperature are not mediated by GDEE-sensitive glutamate receptors.

Induction of wet dog shakes by intracerebroventricular bethanechol in rats. Antagonism by neurotransmitter receptor blockers

Bethanechol chloride, administered intracerebroventricularly, induces a characteristic wet dog shake (WDS) response in rats in a dose-related manner. WDS induced by bethanechol at the dose of 100 micrograms was antagonized by atropine, scopolamine and spiperone (muscarinic cholinergic and dopaminergic antagonists, respectively), whilst metergoline, methysergide, phentolamine, propranolol and bicuculline (serotonergic, alpha-adrenergic, beta-adrenergic and GABA-ergic antagonists) fail to inhibit this effect. The present experiments show that the shaking response may be produced by bethanechol, a potent muscarinic agent administered by the intracerebral route, and suggest that bethanechol-induced shaking behavior in rats may be a useful animal model for delineating agents with antimuscarinic activity.

Dyphenylhydantoin enhancement of diazepam effects on locomotor activity in mice

The interaction of diazepam and diphenylhydantoin on locomotor activity and rearing behavior was studied in mice. Pretreatment of mice with diphenylhydantoin (4.0 and 8.0 mg/kg) significantly reversed the stimulatory effects of low doses of diazepam and considerably increased the depressant effects of the benzodiazepine on locomotor activity and rearing. Neither diazepam (up to 4.0 mg/kg), diphenylhydantoin (8.0 mg/kg) alone, nor combined treatment with both drugs affected brain GABA level and glutamic acid decarboxylase (GAD) activity at any dosage used. The present behavioral and biochemical data suggests that some of the pharmacological effects of diazepam need not be related to GABAergic mechanisms.

Shuttle behavior in rats after lesion of hippocampal pyramidal cells with kainic acid

Rats with bilateral lesions of hippocampal pyramidal cells in the subfield CA 3 with intracerebroventricular kainic acid (0.1 microgram/2 microliter) made more shuttle responses to a buzzer in Pavlovian paradigm, classical conditioning and two-way active avoidance but did not differ remarkably in pseudoconditioning and avoidance conditioning without stimulus pairing, than sham-operated and intact control rats. Animals with unilateral lesion in the CA 3 hippocampal subfield showed no differences in these shuttle situations. The results suggest that CA 3 hippocampal pyramidal cells are of particular importance to the establishment of the stimulus-stimulus relations in the brain.

The effect of intraventricular phenylethylamine and octopamine on the central effects of tremorine and pilocarpine and the acetylcholine level in the rat brain

Phenylethylamine (PEA, 50 and 100 microgram ivc) and octopamine (OCT, 50 and 250 microgram ivc) potentiated the tremorine (10 mg/kg ip) induced hypothermia in the rat. This effect was partially antagonized by atropine (10 mg/kg ip). PEA and OCT significantly prolonged the duration of pilocarpine (100 mg/kg iv) induced catalepsy in rats. PEA (100 microgram ivc) and OCT (250 microgram ivc) depressed the acetylcholine (ACh) level in the cerebral cortex and striatum but did not affect it in the hippocampus. In addition, these amines enhanced the synthesis of ACh in the cerebral cortex, and PEA also in the rat striatum.

(RS)-alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid: wet dog shakes, catalepsy and body temperature changes in rats

(RS)-alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) was microinjected into the lateral brain ventricle of conscious rats in order to evaluate its pharmacological effects. Microinjection (5 microliter) were made unilaterally and the effects of AMPA were assessed for 6 hr. AMPA produced generalized myoclonic seizures, short lasting hypoactivity followed by hyperactivity and hyperthermia when low doses were injected (0.25-1.0 microgram). When AMPA was injected at higher doses (1.5-5.0 microgram) it produced generalized myoclonic seizures, a hypoactive phase and hypothermia rapidly followed by hyperthermia. As the seizure activity and hypoactive phase receded, AMPA at doses of less than 2.5 microgram produced hyperactivity and wet dog shakes in a dose-related manner. After receiving AMPA at doses of 2.5 and 5.0 microgram, rats developed transient catalepsy. High quantities (5.0 microgram) evoked a spectrum of generalized convulsive seizures lasting for 2-3 hr (1 seizure every 15 min). Biochemical assays showed that AMPA had complex effects on brain aminergic systems. AMPA decreased brain NA while brain DA concentration was slightly increased in a dose dependent manner. Moreover, AMPA increased brain 5-HT and 5-HIAA concentration in a dose- and time-related manner.

Effects of some antiepileptic drugs in pentetrazol-induced convulsions in mice lesioned with kainic acid

Mice were injected with intracerebroventricular (i.c.v.) kainic acid (KA; 0.1 micrograms per animal) and the pentetrazol test was carried out on the fifth day after the administration of the amino acid. The following antiepileptic drugs were tested for anticonvulsant activity in mice lesioned with KA: diazepam (0.4 mg/kg), phenobarbital (12.5 and 25 mg/kg), trimethadione (200 and 400 mg/kg), depakine (200 and 400 mg/kg), carbamazepine (10 and 20 mg/kg), lefadol (bromophenylsuccinimide; 20 mg/kg), and acetazolamide (320 mg/kg). All drugs were given intraperitoneally, except for carbamazepine, which was also given orally in doses of 100 and 200 mg/kg. Pentetrazol was administered subcutaneously in a dose of 110 mg/kg, and the animals were subsequently observed for the occurrence of clonic and tonic convulsions within 30 min. The protective effects of diazepam and phenobarbital were significantly reduced in the KA-lesioned animals, while the actions of the remaining anticonvulsants were unaltered. Moreover, a substantial loss of pyramidal cells in the CA 3 field of the hippocampus was noted after i.c.v. injection of KA. It may therefore be concluded that the mechanism of the action of diazepam and phenobarbital are partially dependent on the intact functions of the hippocampal formation.

Effects of morphine and nalorphine on kainic acid-induced hypothermia in rats

Intraventricular administration of kainic acid at the dose of 0.1 microgram induces a significant depression of rectal temperature followed rapidly by its slight elevation. Morphine (40.0 mg.kg-1 IP), which by itself elicited biphasic effect on the body temperature of rats--initially hypothermia followed by hyperthermia--slightly increased the kainic acid-induced hypothermia. Kainic acid did not cause any changes in the hyperthermic effect of low doses of morphine (10.0 mg.kg-1). Pretreatment of rats with nalorphine enhanced the kainic acid-induced hypothermia. On the contrary, nalorphine reversed the hypothermic effect produced by morphine at the dose of 40.0 mg.kg-1. The results suggest that morphine and kainic acid-induced hypothermia are not mediated by the influence on the same type of receptors.

Studies of carbachol-induced wet-dog shake behavior in rats

Intraventricular administration of carbachol chloride evoked wet-dog shakes (WDS) in rats in a dose-related manner. WDS induced by carbachol at the dose of 20 microgram were antagonized by scopolamine, atropine, cyproheptadine, morphine, clonidine, phentolamine, haloperidol, and L-5-hydroxytryptophan (5-HTP). Methergoline, propranolol, bicuculline, and aminooxyacetic acid had no effect on carbachol-induced shaking behavior. The present experiments show the existence of different types of shaking behavior, not exclusively related to the stimulation of central 5-HT structures.

Evidence against the involvement of serotonergic mechanisms in wet dog shake behavior induced by carbachol chloride in rats

The intracerebroventricular administration of carbachol chloride induced a characteristic wet dog shake response in rats. Neither 5,6-dihydroxytryptamine, a serotonergic depletor, nor DL-p-chlorophenylalanine, an inhibitor of 5-HT synthesis, affected wet dog shakes induced by carbachol. Putative antiserotonergic drugs such as cyproheptadine, danitracen and pizotifen antagonized carbachol-induced wet dog shakes, but the 5-HT-receptor antagonist methergoline did not significantly affect the response. These results indicated that carbachol-induced wet dog shakes in rats are probably not related to increased activity of central serotonergic mechanisms. Additionally, the present experiments showed that the anticholinergic properties of the potent serotonergic blockers cyproheptadine, danitracen and pizotifen must be taken into account, and these drugs should be used with care as relatively selective pharmacological tools.

Studies on the latency of rat liver fumarate hydratase

A hypotonic medium and nonionic detergents Triton X-100 and digitonin have no influence on the activity of fumarase in the homogenate or in the mitochondrial fraction either. Ionic detergents of deoxycholate, cholate and sodium dodecyl sulphate exert an inhibiting influence. The activity of enzyme was determined in an L-malate-fumarate system. 1 h of incubation and the original Racker's method gave similar results. The lack of 'latency', found for the mitochondrial fumarase, was discussed basing on the data concerned with the penetration of metabolites through the inner mitochondrial membrane.

Investigation of localization of monoamine oxidase (EC 1.4.3.4) in subfraction of rat liver mitochondria

Subfractionation of the purified preparations of mitochondria was performed according to Schnaitman's digitonin method. In some experiments, polyvinyl sulphate (PVS) was added to the medium during the preparation and subfractionation of mitochondria. The formation of the "fluffy layer" was not observed in the presence of PVS. The "fluffy layer" was either removed or left within the pellet during the separation of the subfraction of mitoplasts from the supernate containing the outer membrane as well as the inter-membrane space. The monoamine oxidase (MAO) activity was determined by means of our own modification of Tabor's method. In this way the influence of aldehyde oxidase upon the obtained results could be eliminated. A part of MAO activity was found in the subfraction of mitoplasts both in the presence and absence of PVS in the medium. The obtained results suggest double localization of MAO both in the outer and inner membrane. The influence of the method of determination of MAO activity on the evaluation of its intra-mitochondrial activity has been discussed.