Spermine attenuates behavioral and biochemical alterations induced by quinolinic acid in the striatum of rats.

Polyamines are aliphatic amines containing nucleophilic centers that are found in all eukaryotic cells, including brain cells. These compounds determine neuroprotection in experimental models of cerebral ischemia and neurotoxicity. In the current study we investigated the protective effects of spermine, an agonist of the polyamine binding site at the N-methyl-d-aspartate receptor, against the behavioral and neurochemical alterations induced by quinolinic acid. The unilateral intrastriatal injection of quinolinic acid (180 nmol/site into the dorsal striatum) induced stereotypical motor asymmetries, assessed by the open field and elevated body swing tests. Spermine modulated quinolinic acid-induced rotational behavior biphasically. While the previous intrastriatal administration of spermine at the dose of 0.1 nmol/site increased, the administration of spermine at the dose of 10 nmol/site reduced quinolinic acid-induced rotational behavior. Spermine (10 nmol/site) also decreased the contralateral swing behavior induced by quinolinic acid. Furthermore, the effect of 10 nmol of spermine was counteracted by the co-administration of arcaine (10 nmol), a selective antagonist of the polyamine binding site at the N-methyl-d-aspartate receptor. In addition, spermine (10 nmol) protected against quinolinic acid-induced protein carbonylation in the rat striatum, further suggesting an antioxidant role for this polyamine. These results provide evidence that the behavioral and biochemical alterations induced by quinolinic acid are attenuated or prevented by spermine through its interaction with N-methyl-d-aspartate receptor and/or its antioxidant function.

Nerve growth factor selectively prevents excitotoxin induced degeneration of striatal cholinergic neurones.

Selective neuronal death is a prominent feature of human neurodegenerative disease both of genetic and idiopathic origin. Huntington's disease is characterised by the selective degeneration of striatal projection neurones, with the relative preservation of a variety of interneurones. The ability of the endogenous excitotoxin, quinolinic acid, to produce a pattern of selective neuronal cell death was investigated using immunocytochemical and histochemical techniques. We find that the large striatal, cholinergic interneurones are relatively spared, and that this sparing can be enhanced by the co-administration of the neurotrophin, nerve growth factor (NGF). Further, a single co-injection of NGF will selectively prevent both the cell death and morphological changes that occur within cholinergic cells when assessed 2 weeks later. These results suggest that an interaction between growth factors and excitotoxins can dramatically modify patterns of selective neuronal death.

A peptidase-resistant cyclic octapeptide analogue of somatostatin (SMS 201-995) modulates seizures induced by quinolinic and kainic acids differently in the rat hippocampus.

Electroencephalographic (EEG) seizures were measured in rats after intrahippocampal injection of 120 nmol quinolinic acid into the stratum radiatum CA1 or 0.19 nmol kainic acid in the dentate gyrus or in the stratum radiatum. Injection of 5 micrograms SMS 201-995, a peptidase-resistant cyclic octapeptide analogue of somatostatin, into the stratum radiatum, 15 min before quinolinic acid, did not significantly modify the number of seizures and the total time in seizures. Five micrograms SMS 201-995 injected into the stratum radiatum reduced the number of seizures induced by kainic acid in the same area and the total time spent in seizures by 58% and 75%, respectively (Student's t-test; P less than 0.01). In both instances the latency to the first ictal episode was not significantly modified. Lesions of the medial septum, which reduced the activity of choline-o-acetyl-transferase (CAT) in the dorsal hippocampus by greater than 90% after one week did not significantly affect seizures induced by quinolinic acid. In rats lesioned in the medial septum, 5 micrograms SMS 201-995 reduced the total time spent in seizures by 43%, without changing the number of ictal episodes and raised the latency to the first quinolinic acid-induced seizure by 53% (ANOVA 2 x 2, P less than 0.05) but had no effect on these measures in the corresponding sham-operated group.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of MK-801, ketamine and alaptide on quinolinate models in the maturing hippocampus.

The ability of the N-methyl-D-aspartate receptor antagonists, MK-801, ketamine and alaptide [a newly synthesized cyclo(1-amino-1-cyclopentane-carbonyl-L-alanyl) with protective properties in models of hypoxia], to prevent neuronal degeneration caused by intracerebroventricular application of quinolinic acid was investigated. Neurodegenerative effects of quinolinate in the hippocampal formation were found to increase with the degree of maturity of glutamatergic target structures. A protective potency of the N-methyl-D-aspartate receptor antagonists was observed at all developmental stages studied (12- and 30-day-old and adult rats). MK-801 showed the highest efficacy, alaptide the lowest. These findings suggest a parallelism in maturity of glutamatergic transmission processes as one prerequisite of quinolinate vulnerability and postnatal increases of target fields of the protectives. Application of MK-801 or ketamine after quinolinate injection intensified their protective effects when compared to simultaneous or preadministration. This observation is interpreted as indicating that quinolinate is a prompter of a delayed neurodegenerative process rather than acting immediately as a toxicant.

Intracerebral implantation of nerve growth factor-producing fibroblasts protects striatum against neurotoxic levels of excitatory amino acids.

With the exception of L-DOPA pharmacological treatment in Parkinson's disease, the neurodegenerative diseases lack effective treatment. Previous studies of neurodegenerative diseases suggest that symptoms arise secondary to defects in local neuronal circuitry and cannot be treated effectively with systemic drug delivery. Therefore, a promising treatment is the application of fetal or genetically engineering cells which protect or replace neurons in deficient regions. Engineered cells can be derived from cell lines or grown from recipient host fibroblasts or other cells, then modified to produce and secrete substances at a specific area of the brain. A previous study using parallel intracerebral infusions of nerve growth factor and an excitotoxic amino acid into the rat striatum demonstrated a protective effect of nerve growth factor on neurons [Aloe L. (1987) Biotechnology 5, 1085-1086]. In order to further test this paradigm, we have utilized a biological delivery system of nerve growth factor by implanting fibroblasts into the rat striatum which secrete high levels of nerve growth factor, prior to infusing the neurotoxins quinolinate or quisqualate. Animals in this group had smaller lesions than did a group implanted with a similar non-nerve growth factor-producing graft. In addition, marked neuronal sparing was noted within areas of lesions in those animals containing a nerve growth factor-producing graft. These results indicate that implantation of genetically engineered nerve growth factor-secreting cells can be used to protect neurons at a specific target from excitotoxin-induced lesions.

Protective effect of nimodipine against quinolinic acid-induced damage of rat hippocampus in vitro.

The study was undertaken to examine the effect of nimodipine, calcium channels blocker, on the morphological alterations induced by quinolinic acid (QUIN). The experiment was performed on 21-day-old organotypic rat hippocampal cultures. Nimodipine was applied to the nutrient medium simultaneously with QUIN (both at 100 microM). Ultrastructural changes were evaluated 24 h, 5 and 7 days after the exposure to tested agent. It was shown that nimodipine induced distinct cytoprotective effect, especially considering the development of late neurotoxic injury produced by QUIN. However, the protection was not complete, indicating the participation of the other factors in the pathomechanism underlying structural damage produced by QUIN.

Kynurenic acid antagonizes hippocampal quinolinic acid neurotoxicity: behavioral and histological evaluation.

In the present study, we evaluate the ability of kynurenic acid to protect hippocampal neurons from the neurotoxicity of the N-methyl-D-aspartate (NMDA) agonist quinolinic acid. Bilateral intrahippocampal injection of quinolinic acid (120 nmol) led to severe behavioral disturbances and total loss of hippocampal neurons. Intrahippocampal co-injection of kynurenic acid (360 nmol) completely prevented cell loss and behavioral disturbances. However, the protection was incomplete when kynurenic acid was intraperitoneally injected (500 mg/kg, repeated during 4 days). These above results indicate that kynurenic acid can antagonize the neuronal degeneration mediated by excessive stimulation of NMDA receptors in vivo.

Modulation of neuronal activity of locus coeruleus in rats induced by excitatory amino acids.

The excitatory actions on the unit activities of locus coeruleus induced by excitatory amino acids were studied. Quinolinic acid 10 nmol and N-methyl-D-aspartate (NMDA) 4 nmol icv markedly increased unit discharge of locus coeruleus neurons. The excitatory action was fully antagonized by icv 4 nmol D,L-2-amino-7-phosphonoheptanoic acid, a specific NMDA receptor antagonist. Excitatory effect induced by quinolinic acid is possibly mediated by excitatory amino acid receptors in locus coeruleus.

[Anticalcium preparations that prevent the neurodegenerative action of quinolinic acid]. / Antikal'tsievye preparaty, preduprezhdaiushchie neirodegenerativnoe deistvie khinolinovoi kisloty.

The protective effect of anticalcium drugs on the development of quinolinate destruction in the dorsal hippocampus and nuclei of the lateral septum was studied on rats with the cannulae chronically implanted into the lateral ventricles. It was found that single doses of kynurenic acid (50 micrograms), taurine (300 micrograms) and verapamil (25 micrograms) prevented the destructive effect of quinolinic acid (30 micrograms) during central administration whereas cinnarizine (25 micrograms) and corinfar (15 micrograms) were active in oral 8-day-long administration.

Prevention of quinolinic acid neurotoxicity in rat hippocampus in vitro by zinc. Ultrastructural observations.

The effect of zinc on the development and evolution of quinolinic acid-induced alterations in the rat hippocampus in culture was studied ultrastructurally. Zinc, although it possesses intrinsic cytotoxic properties, after application in concentrations comparable with those encountered in vivo, was able to prevent typically observed responses after quinolinic acid exposure, either early or late damage to hippocampal neurons. The results further support the concept of a potential protective effect of zinc against the neurotoxicity of particular excitotoxins.

Quinolinate neurotoxicity and glutamatergic structures.

Neurotoxic properties of quinolinic acid following intracerebroventricular application were investigated in the hippocampal formation of 12- and 30-day-old rats. Quinolinic acid neurodegenerative potency was found to depend on the survival time, the dose applied and the developmental stage of the animal. Pretreatment with kynurenic acid and ketamine as well as the transection of the perforant path were noted to protect major parts of the hippocampal cell layers from quinolinic acid-induced degenerative effects. The results are interpreted in view of a putative dependence of quinolinic acid neurotoxicity on the presence of established synaptic, in particular glutamatergic, processes which play a major role in the hippocampal formation and mature during the first postnatal weeks. For comparison, we studied local effects of quinolinic acid on superior cervical and dorsal root ganglia in which glutamate inputs obviously do not occur; no signs of neuronal vulnerability were seen.

Systemic treatments with GM1 ganglioside reduce quinolinic acid-induced striatal lesions in the rat.

The administration of GM1 ganglioside, 30 mg/kg per day i.p., begun 3 days prior to an intrastriatal injection of the excitotoxic tryptophan metabolite quinolinic acid (QUIN) and continued for 8-16 days thereafter, significantly decreased QUIN-induced striatal damage, as evaluated by measuring the activity of the marker enzymes, choline acetyltransferase and L-glutamic acid decarboxylase. Since an increased production of QUIN has been demonstrated in Huntington's chorea patients it is possible that repeated GM1 administration could reduce the occurrence of progressive striatal neuronal loss in this neurological disorder.

Behavioral evaluation of the anti-excitotoxic properties of MK-801: comparison with neurochemical measurements.

The ability of MK-801 to protect striatal neurons from the excitotoxic action of quinolinic acid was evaluated by means of apomorphine-induced rotational behavior and by measurement of striatal choline acetyltransferase (ChAT) and glutamic acid decarboxylase (GAD) activity, neurochemical markers for cholinergic and GABAergic neurons, respectively. Animals with a unilateral quinolinic acid lesion of the striatum exhibited a vigorous rotational response when challenged with apomorphine (0.5 mg/kg, s.c.) 6 days later and were found to have an 88 90% depletion of striatal ChAT and GAD activity. Treatment with a high dose of MK-801 (10 mg/kg, i.p.) prior to intrastriatal injection of quinolinic acid eliminated the subsequent rotational response to apomorphine and resulted in complete protection of striatal ChAT and GAD activity. Lower doses of MK-801 (1, 3 and 5 mg/kg, i.p.) failed to significantly reduce the rotational response to apomorphine but provided partial, dose-dependent protection of both ChAT and GAD activity. The rotational response to apomorphine correlated with the percent reduction in both ChAT activity (r = 0.57, P less than 0.0005) and GAD activity (r = 0.49, P less than 0.0005). Rotational behavior may thus provide a means to evaluate the functional integrity of the striatum.

[Effects of antagonists of exciting amino acids on the neuro-destructive effect of quinolinic acid in vitro in comparison with their anticonvulsive action in situ]. / Vliianie antagonistov vozbuzhdaiushchikh aminokislot na neirodestruktivnyi éffekt khinolinovoi kisloty in vitro v sopostavlenii s ikh antikonvul'sivnymi deistviem in situ.

A comparative study of the influence of kynurenic acid (KYNA), L-kynurenine (KYN) and ethylimidazole-4-5-dicarboxylic acid (IEM-1442) on neuro-destructive effect of quinolinic acid (QUIN) in hippocampal cell cultures of mouse embryos and on convulsive action of QUIN after its injection into the brain ventricles of adult mice was performed. In presence of KYNA the neuronal destruction in vitro didn't occur under QUIN exposure, while in situ KYNA had no effect on convulsive action of QUIN. On the other hand, KYN and IEM-1442 didn't block the neurodegenerative action of QUIN in vitro, whereas in situ these compounds showed the anticonvulsant, effect. The results obtained suppose, that some anticonvulsants, preventing convulsive effects of QUIN, are not antagonists of the receptors, which mediate its neurodegenerative action.

Kynurenic acid and AP5 distinguish between NMDA receptor agonists.

Quantitative analysis of responses to amino acids in mouse cortical slices has indicated that the antagonists kynurenate and 2-amino-5-phosphonopentanoic acid distinguish between ibotenate and both N-methyl-D-aspartate (NMDA) and quinolinate. This result is consistent with the existence of NMDA-receptor subtypes.

Neuroprotective effects of MK-801 in vivo: selectivity and evidence for delayed degeneration mediated by NMDA receptor activation.

The ability of the noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 to prevent neuronal degeneration in the rat striatum and hippocampus caused by intracerebral injection of excitotoxins has been examined. Excitotoxic damage was assessed after 7 d, using histological and biochemical [choline acetyltransferase (ChAT) glutamate decarboxylase (GAD)] measurements. Systemically administered MK-801 was found to protect against neurodegeneration caused by NMDA (200 nmol) and the naturally occurring NMDA receptor agonist quinolinate (120-600 nmol) but not against that induced by kainate (5 nmol) or alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA; 50 nmol), indicating a selectivity for NMDA receptor-mediated neuronal loss. Neurotoxicity caused by NMDA (200 nmol) or quinolinate (200 nmol) was prevented by MK-801 (1-10 mg/kg, i.p.) administered in a single dose after excitotoxin injection. In the striatum, significant protection of cholinergic neurons (assessed by ChAT measurements) was observed when MK-801 was given up to 5 hr after injection of NMDA or quinolinate, whereas protection of GABAergic neurons (assessed by GAD measurements) was obtained up to 2 hr. The results suggest that GABAergic neurons degenerate more rapidly than cholinergic neurons. The competitive NMDA receptor antagonist 3-[(+/-)-2-carboxypiperazin-4-yl]-propyl-1-phosphonate (100 mg/kg, i.p.) gave partial protection of striatal neurons when administered 1 hr after quinolinate injection. In the rat hippocampus, administration of 10 mg/kg MK-801 i.p. 1 hr after quinolinate injection caused almost complete protection of pyramidal and granule neurons, whereas the degeneration of CA3/CA4 pyramidal neurons caused by kainate injection was unaffected. These observations indicate that neurons in rat striatum and hippocampus do not die as an immediate consequence of exposure to high concentrations of NMDA agonists but that a delayed process is involved that requires NMDA receptor activation. In this respect, intracerebral injections of NMDA agonists may mimic the pathological changes that are thought to occur in the brain following periods of cerebral ischemia, where delayed neuronal degeneration occurs.

Systemic approaches to modifying quinolinic acid striatal lesions in rats.

Quinolinic acid (QA) is an endogenous excitotoxin present in mammalian brain that reproduces many of the histologic and neurochemical features of Huntington's disease (HD). In the present study we have examined the ability of a variety of systemically administered compounds to modify striatal QA neurotoxicity. Lesions were assessed by measurements of the intrinsic striatal neurotransmitters substance P, somatostatin, neuropeptide Y, and GABA. Histologic examination was performed with Nissl stains. The antioxidants ascorbic acid, beta-carotene, and alpha-tocopherol administered s.c. for 3 d prior to striatal QA lesions had no significant effect. Other drugs were administered i.p. 1/2 hr prior to QA striatal lesions. The following were ineffective in blocking QA excitotoxicity: allopurinol, 50 and 100 mg/kg; ketamine, 75 mg/kg; nimodipine, 2.4, and 10 mg/kg; baclofen, 10 mg/kg; 2-amino-5-phosphonovalerate, 50 mg/kg; and 2-amino-7-phosphonoheptanoate, 50 mg/kg. Oral taurine administration for 4 weeks resulted in significantly increased levels of brain taurine but had no significant effect in blocking QA neurotoxicity. Systemic administration of the noncompetitive N-methyl-D-aspartate (NMDA) antagonist MK-801 resulted in a dose-responsive protection against QA toxicity, with complete block at a dose of 4 mg/kg. If the pathogenesis of HD involves QA or another excitotoxin acting at the NMDA receptor, it is possible that MK-801 could retard the degenerative process.

Episodic barrel rotations induced by intrastriatal injection of quinolinic acid in rats. Inhibition by anticonvulsants.

Unilateral intrastriatal injection of quinolinic acid (2,3 pyridine dicarboxylate; QUIN) in the rat produces episodic barrel rotations and tonic-clonic forepaw movements, lasting for several hours. We investigated whether intraperitoneal posttreatment with anticonvulsants could abolish this phenomenon when it is already fully developed, and whether their potency ratio was similar in models of epilepsy. All 8 tested antiepileptics, namely carbamazepine, clonazepam, diazepam, diphenylhydantoin, ethosuximide, flunarizine, phenobarbital and sodium valproate decreased this behaviour in a dose-dependent way. Six other drugs with anticonvulsant properties were also effective: DL-2-amino-7-phosphonoheptanoic acid, desipramine, etomidate, ketamine, meprobamate and sabeluzole. The ED50-values for halving the frequency of the episodes of barrel rotation correlated well with published ED50-values for inhibition of tonic hindpaw extension in the maximal metrazol seizure test (rs = .95, p less than 0.001) and with the ED50-values for halving the duration of the forepaw clonus in the rat-kindling model (rs = .93, p less than 0.001). This quinolinic acid test allows visualization of the onset of action of anticonvulsants, with each animal as its own control. In order to assess whether this test is also sensitive to drugs influencing the symptoms of Huntington's disease, the effect of the dopamine antagonists haloperidol and pimozide, the acetylcholinesterase inhibitor physostigmine and the anticholinergics atropine and dexetimide were investigated as well. The experiments suggested that the barrel rotations and clonic forepaw movements, only 3-6 hours after intrastriatal injection of QUIN respond to anticonvulsants, but are not specifically sensitive to drugs used in the symptomatic treatment of Huntington's disease.

[Selective anticonvulsive action of N-substituted imidazole-4,5-dicarboxylic acids against quinolinic acid]. / Izbiratel'noe protivosudorozhnoe deistvie N-zameshchennykh imidazol-4,5-dikarbonovykh kislot protiv khinolinovoi kisloty.

Selective antagonists of quinolinic acid (2,3-pyridine dicarboxylic acid, QUIN)--an endogenous convulsant tryptophan metabolite, administered intracerebroventricular to mice, were identified during comparison with the following intracerebroventricular convulsants: l-kynurenine, aspartic, glutamic, N-methyl-DL-aspartic and kainic acids. It is suggested that the antagonism arises due to a common fragment of the structure which consists of two carboxylic groups at two nearest carbon atoms of the ring and of one nitrogen atom in the alpha-position. The selective action of the compounds found against QUIN supports the suggestion that QUIN produces seizures via N-methyl-D-aspartate binding sites.

[3H]norepinephrine release from hippocampal slices is an in vitro biochemical tool for investigating the pharmacological properties of excitatory amino acid receptors.

[3H]Norepinephrine ([3H]NE) efflux from preloaded rat hippocampal slices was increased in a dose-dependent manner by excitatory amino acids, with the following order of potencies: N-methyl-D-aspartate (NMDA) greater than kainic acid (KA) greater than L-glutamate greater than or equal to D,L-homocysteate greater than L-aspartate greater than quinolinic acid greater than quisqualic acid. The effect of the excitatory amino acids was blocked by physiological concentrations of Mg2+, with the exception of KA. D,L-2-Amino-7-phosphonoheptanoic acid dose-dependently inhibited the NMDA effect (ID50 = 69 microM), whereas at 1 mM it was ineffective versus KA. The release of [3H]-NE induced by quinolinic acid was blocked by 0.1 mM D,L-2-amino-7-phosphonohepatanoic acid. gamma-D-Glutamylglycine dose-dependently inhibited the KA effect with an ID50 of 1.15 mM. Tetrodotoxin (2 microM) reduced by 40 and 20% the NMDA and KA effects, respectively. The data indicate that [3H]NE release from hippocampal slices can be used as a biochemical marker for pharmacological investigations of excitatory amino acid receptors and their putative agonists and antagonists.