Intrastriatal Kainic Acid Research Articles

Functional and biochemical characteristics of a putative quisqualate-type receptor in rat striatum: effect of brain lesions.

Excitatory amino acids such as L-glutamate (Glu) and quisqualate (QUIS) markedly potentiated K+-evoked release of exogenous [3H]dopamine (DA) from rat striatal slices. Intrastriatal kainic acid injections resulted in a total disappearance of the stimulatory effects of Glu on evoked-release of [3H]DA as well as in a parallel reduction in the maximal number (Bmax) of a D-aspartate-insensitive L-[3H]Glu binding site in striatal particulate fractions. Following cortical ablation, the potentiating effect of Glu on [3H]DA release in decorticated striatal slices lasted longer, compared to normal slices, and occurred during the 2nd min following K+-depolarization. However, the extent (%) of Glu stimulation on [3H]DA release remained the same in decorticated and normal striatal slices. Cortical ablation produced also a significant decrease in the Bmax and in the KD' of the D-aspartate-insensitive binding site towards L-[3H]Glu. These results support the proposal that the D-aspartate-insensitive Glu binding site is somehow related to an amino acid receptor-mediated modulation of dopaminergic transmission in the rat corpus striatum.

Distant blood-brain barrier opening in subfields of the rat hippocampus after intrastriatal injections of kainic acid but not ibotenic acid

Blood brain barrier (BBB) permeability towards proteins was determined in rats 4 h after intrastriatal kainic or ibotenic acid application, using Evans blue as indicator. Whereas, with the exception of the unspecific damage in cortex, after ibotenic acid BBB remained intact in deep brain areas, Evans blue leakage was found ipsilateral to the kainic acid injection, occasionally in striatum, thalamus and amygdala and regularly in hippocampus. There it was confined to the fimbria and the CA3 field. Only rarely a mirror focus-like staining was present in the contralateral hippocampus. The ultrastructural investigation revealed that BBB opening in CA3 is due to increased transendothelial pinocytosis; the tight junctions were intact. Thus, changes in the microenvironment around vessels, elicited by kainic acid and/or seizures, might be responsible for BBB opening.

Activities of glutamine synthetase, glutaminase and arginase in kainic acid lesioned rat brain corpus striatum

Intrastriatal kainic acid (2 μg/μl) administration gave rise to significant increase in activities of glutamine synthetase and arginase along with a significant decrease in the activity of glutaminase in the lesioned striatal tissue 7 days after the administration of kainic acid. The increase in the activity of glutamine synthetase was attributed to the gliosis occurring in such lesions. The decrease in the activity of glutaminase was thought to be due to the loss of GABAergic neurons. The increase in arginase activity might be occurring in glial cells or in nerve endings. Although the earlier results indicated a low specific activity of arginase in glial cells, the observed increase in its activity might be partly due to its increase in proliferating glial cells, liberating ornithine for the formation of polyamines. However, it was also thought that a substantial increase may be occurring in the arginase present in the intact glutamatergic (corticostriate pathway) nerve endings, since it was earlier found that the synaptosomes of the rat brain had appreciably high activity of arginase. These results were discussed in relation to the probable roles of arginine and glutamine as the precursors for neurotransmitter pools of glutamate in striatum.

Effects of intrastriatal kainic acid injection on [3H]dopamine metabolism in rat striatal slices: evidence for postsynaptic glial cell metabolism by both the type A and B forms of monoamine oxidase.

Abstract: Intrastriatal injections of kainic acid (KA) were utilized to investigate the cellular localization of postsynaptic dopamine (DA) metabolism by type A and B monoamine oxidase (MAO) in rat striatum. At 2 days postinjection, maximal degeneration of cholinergic and γ‐aminobutyric acid (GABA)ergic neurons was observed and found to be associated with a significant decrease in both type A and B MAO activity. However, over the next 8‐day period, when only the process of gliosis appeared to be occurring, a selective return to control of type B MAO activity was seen. When the metabolism of [3H]DA (10−7 M) was examined in 8‐day KA‐lesioned rat striatal slices, an increase in [3H]dihydroxyphenylacetic acid (DOPAC) and [3H]homovanillic acid (HVA) formation was observed. The KA‐induced elevation of [3H]DOPAC formation (but not [3H]HVA) was abolished by the DA neuronal uptake inhibitor nomifensine. This is consistent with earlier findings suggesting that HVA is formed exclusively within sites external to DA neurons. Experiments with clorgyline and/or deprenyl revealed that the relative roles of type A and B MAO in striatal DA deamination remained unchanged following KA (90% deamination by type A MAO) even though total deamination was substantially enhanced. At high concentrations of [3H]DA (10−5 M), deamination by type B MAO could be increased to 30% of the total MAO activity; however, this was observed in both control and KA‐lesioned striata. These results suggest that KA‐sensitive neurons contain type A and/or type B MAO. Moreover, whereas these neurons may metabolize DA, a major portion of postsynaptic DA deamination appears to occur within glial sites of rat striatal tissue. Furthermore, glial cells would appear to contain functionally important quantities of both type A and B MAO.

Evidence for dopamine autoreceptors controlling dopamine synthesis in the substantia nigra

The effect of apomorphine and haloperidol on DOPA accumulation after inhibition of DOPA decar☐ylase activity with NSD 1015 was compared in the substantia nigra (SN) and caudate nucleus (CN) of normal rats and rats deprived of nigral afferences from the striatum by means of intrastriatal kainic acid. In normal rats apomorphine decreased DOPA accumulation to the same extent in both the SN and CN. However, haloperidol produced a more pronounced increase in DOPA accumulation in the CN than in the SN. The effect of both drugs still persisted in the SN and CN after destruction of the neuronal strionigral feedback loop with kainic acid. The results provide evidence for the existence of nigral dopamine autoreceptors controlling dopamine synthesis in the SN.

Effects of kainic acid injection and cortical lesion on ornithine and aspartate aminotransferases in rat striatum.

The effects of cortical lesions and intrastriatal kainic acid injections on various striatal enzyme activities were investigated. Ornithine aminotransferase decreased concomitantly with glutamate uptake in decorticated and chronic kainic acid-treated rats. It was also decreased in acute kainic acid-lesioned striatum where glutamate uptake was unaffected. Aspartate aminotransferase, however, decreased only after acute kainic acid treatment. Results for glutamate uptake, glutamate decarboxylase, and choline acetyltransferase were in agreement with previous findings. These results suggest that ornithine may act as a precursor for glutamate in nerve terminals, although the nonspecific localization does not allow ornithine aminotransferase to be a convenient biochemical marker. The decrease in aspartate aminotransferase is thought to be due to the widespread cell degeneration after acute kainic acid. Aspartate aminotransferase activities were also found to be reduced in the frontal cortex, caudate nucleus and putamen of Huntington's disease brains.

Kainic acid-induced changes of serotonin and dopamine metabolism in the striatum and substantia nigra of the rat

Levels of the putative neurotransmitters serotonin (5-HT) and dopamine (DA) and their respective metabolites 5-hydroxyindoleacetic acid (5-HIAA) and dihydroxyphenylacetic acid (DOPAC) were determined in the rat striatum after unilateral intrastriatal injection of the convulsive neurotoxin kainic acid. Two days after intrastriatal kainic acid injection, levels of the 5-HT metabolite 5-HIAA were increased by about 200% in the injected striatum and by about 150% in the contralateral striatum. An elevated striatal 5-HIAA content was still detectable 10 days after the kainate lesion, but approached normal values 10 weeks after the injection of the neurotoxin. Two days after the lesion, but not at the other time intervals, a moderate increase of 5-HIAA also occurred bilaterally in other brain areas such as the substantia nigra, frontal cortex and hypothalamus. Levels of 5-HT were decreased significantly in the injected striatum 2 days after the intrastriatal application of kainic acid and increased by about 40% after 10 weeks. The 5-HT concentration in the contralateral striatum or in the three other brain areas examined was unchanged at all time intervals. Levels of the DA metabolite DOPAC and DA turnover were increased in the lesioned striatum 2 days after kainic acid injection; concomitantly the DOPAC level was increased in the substantia nigra of the contralateral side. DOPAC levels of the contralateral striatum were unchanged or slightly reduced 2 days after the injection. Ten days as well as 10 weeks after the lesion there was a slightly increased DOPAC concentration in both striata. The levels of DA were not altered at any time interval after the injection of kainic acid.

Studies on axonal transport in dopaminergic neurons: Effect of neuropharmacologic lesions

Axonal transport of [ 3H]protein to the nucleus accumbens, olfactory tubercle, septal region, caudate nucleus, and hypothalamic region was investigated in rats after unilateral injection of [ 3H]lysine into the substantia nigra. Co-injection of 2 μg of colchicine with the [ 3H]lysine depressed the recovery of [ 3H]protein from forebrain structures by over 70 percent without altering incorporation into midbrain protein, whereas 1 or 2 μg of cycloheximide decreased the incorporation of labelled lysine into both midbrain and forebrain protein by 69 to 76 percent. Partial 6-hydroxydopamine (6-OHDA)-induced lesions of the substantia nigra decreased striatal dopamine levels by 78 percent and reduced axonal protein transport by 47 to 82 percent. Injecting the [ 3H]lysine 2 mm dorsal to the substantia nigra decreased transport by 95 percent. Unilateral kainic acid-induced lesions of the caudate, which decreased striatal glutamic acid decarboxylase activity by 44 percent and spared striatal dopamine content, did not alter the transport of [ 3H]protein. Thus, axonal transport of protein in dopamine-containing systems is dependent upon the site of injection of labelled precursor and upon the integrity of a 6-OHDA sensitive pathway. Further, transport is sensitive to inhibitors of both microtubule assembly and protein synthesis, and insensitive to intrastriatal kainic acid lesions.

Presynaptic dopamine receptors: insensitivity to kainic acid and the development of supersensitivity following chronic haloperidol.

The effects of kainic acid lesions and chronic haloperidol treatment on rat striatal dopaminergic presynaptic receptors were studied. Following the gamma-butyrolactone-induced inhibition of dopaminergic impulse flow, and after dopa decarboxylase inhibition, dopa accumulation and its reversal by dopamine agonists was measured in vivo. 3H-apomorphine (a dopamine receptor ligand with purported presynaptic specificity) was used for in vitro binding experiments. Presynaptic dopamine receptors, as assessed by both methods, were unaffected by intrastriatal kainic acid injection 5-6 days before sacrifice. Seven days after termination of chronic haloperidol treatment (28 days, 0.5 mg/kg/day s.c.) both an increased apomorphine response using the dopa accumulation method and an increase in 3H-apomorphine binding were observed, indicating the development of presynaptic dopamine receptor supersensitivity.

Tremor: Role of striatal cholinergic neurons and the effect of intrastriatal kainic acid

Rats injected intrastriatally with kainic acid (KA) showed increased tremor responses to arecoline and tremorine, but not to harmaline. Since KA significantly reduced both pre- and postsynaptic measurements of cholinergic function in the striatum, the results indicate that integrity of the striatal cholinergic system is not essential to tremor response. Further investigations of cholinergic function in the brains of rats injected with KA did not reveal evidence of cholinergic supersensitivity; thus, the altered responses to cholinergic agents may reflect KA-associated destruction of some pathway normally opposing the behavioral output of cholinergic stimulation. If, as recently proposed, intrastriatal injection of KA produces an animal model of Huntington's disease (HD), then these results may also be relevant to experimental therapeutics of this disorder.

The localization of receptor binding sites in the substantia nigra and striatum of the rat

Neurotransmitter receptor binding of 5 ligands was examined in the striatum, substantia nigra (SN) and frontal cortex of rats which had received either unilateral 6-hydroxydopamine (6-OHDA) lesions of the nigrostriatal pathway (NSP) or unilateral kainic acid lesions of the striatum. 6-OHDA lesions of the NSP significantly reduced [ 3H]dihydroalprenolol ([ 3H]DHA) and [ 3H]naloxone binding by 31% and 28% respectively, in the denervated striatum compared to the contralateral side. Scatchard analysis revealed that the alteration in [ 3H]DHA binding was not due to a change in the affinity of the β-adrenergic receptor for [ 3H]DHA. In marked contrast to these changes in the striatum, destruction of the NSP resulted in a significant increase in [ 3H]DHA and [ 3H]Nal binding by 44% and 26%, respectively, in the frontal cortex of the lesioned compared to the control side. 6-OHDA lesions in the NSP did not alter striatal receptor binding for [ 3H]quinuclidinyl benzilate ([ 3H]QNB), [ 3H]muscimol ([ 3H]Mus) or [ 3H]flunitrazepam ([ 3H]Flu). Similarly, intrastriatal kainic acid injections did not alter striatal receptor binding for [ 3H]Nal, [ 3H]Flu or [ 3H]Mus. Of the various receptor densities measured in the SN after the above lesions the only alteration observed was a 43% increase in [ 3H]Flu binding following 6-OHDA lesions of the NSP. Scatchard analysis indicate no change in the affinity of the benzodiazepine receptor for [ 3H]Flu. 6-OHDA lesions of the NSP did not alter [ 3H]QNB or [ 3H]Nal binding in the SN. Striatal kainic acid lesions did not alter nigral [ 3H]QNB or [ 3H]Flu binding. The results are discussed in terms of neurotransmitter localization and plasticity within the striatum, SN and frontal cortex.

Reduction of endogenous level, uptake and release of taurine after intrastriatal kainic acid injection

Rats received single unilateral stereotaxic injections of 2 μg of kainic acid into the left caudate nucleus 10 days before sacrifice. On the lesioned side, a significant reduction of endogenous taurine levels and high affinity uptake of 3H-taurine into crude synaptosomal (P 2) fractions to about 75% of control values was found. In agreement with previous reports on the neurotoxic action of kainic acid, a marked reduction of endogenous GABA levels and 14C-GABA uptake into P 2-fractions was observed, while 3H-dopamine uptake was not significantly changed. In superfusion experiments with prelabeled P 2-fractions prepared from lesioned striata, K +(56 mM)-induced release of 3H-taurine and 14C-GABA, but not of 3H-dopamine, was reduced. The results are compatible with the hypothesis that taurine in the striatum of the rat is partially localized in interneurones.

Effect of kainic acid injections and other brain lesions on vasoactive intestinal peptide (VIP)-stimulated formation of cAMP in rat brain

In rat striatal slices, both intrastriatal kainic acid injection, which destroys striatal neurones, and intranigral injection of 6-hydroxydopamine (6-OHDA), which leads to a degeneration of dopamine nerve terminals in the striatum, reduced vasoactive intestinal peptide (VIP)-induced cAMP accumulation by approximately 60%. Cortical ablation, which leads to degeneration of cortico-striatal fibres, had no effect on striatal VIP-induced cAMP formation. Knife cut lesions transecting the stria terminalis, which destroy afferent fibres to the amygdala, decreased the VIP-induced increase in cAMP in amygdala slices by 40%, while kainic acid injection into the amygdala had no effect. Kainic acid injection into several other brain regions, including hippocampus, cortex and hypothalamus also failed to affect the VIP-elicited increase in cAMP in slices, despite reductions in choline acetyl-transferase, glutamate decarboxylase, cyclic nucleotide phosphodiesterase and basal levels of cAMP. The results of a study of the effects of various VIP fragments on cAMP stimulation in striatal and cortical slices suggests that the entire sequence of VIP is necessary for full activity. The results suggest that VIP may be involved in neuromodulation or neurotransmission in the striatum and/or nigrostriatal pathway and also in the stria terminalis from the bed nucleus to the amygdala.

Angiotensin-converting enzyme in substantia nigra: Reduction of activity in huntington's disease and after intrastriatal kainic acid in rats

The substantia nigra of Huntington's disease brains shows a 78% reduction in angiotensin-converting enzyme activity in the pars reticulata and a 48% reduction in the pars compacta. The nucleus accumbens shows a 29% reduction in converting enzyme activity. In the rat, after instrastriatal injections of kainic acid 92.5 μg), an agent which selectively destroys neuronal cell bodies, there is a 55% reduction in angiotensin-converting enzyme activity in the ipsilateral substantia nigra. Both human and animal data suggest that a major part of the angiotensin-converting enzyme in the substantia nigra is localized in nerve terminals whose cell bodies originate in the striatyum.

Functional interaction between receptors for dopamine antagonists and GABA central receptors

The plasticity of GABA receptors has been demonstrated after different pharmacological treatments. Intrastriatal kainic acid injection induces a significant increase of 3H -GABA and 3H -spiroperidol binding both in striatum and substantia nigra. On the other hand, a single injection of ha l operidol decreases in a dose dependent manner 3H -GABA binding both in striatum and cerebellum but not in substantia nigra. Other neuroleptics such as chlorpromazine and sulpiride induce the same changes in 3H-GABA binding, while clozapine tend to increase the GABA radioreceptor binding.

Receptor-linked cyclic amp systems in rat neostriatum: Differential localization revealed by kainic acid injection

Various receptor-linked cyclic AMP systems were measured in rat neostriatum 2–14 days after selective destruction of neuronal cell bodies and dendrites by microinjection of 3 μg of kainic acid. Basal adenylate cyclase activity was reduced by up to 56% in the injected side and the sensitivity to dopamine was abolished. Up to 84% of cyclic nucleotide phosphodiesterase activity, hydrolyzing either cyclic AMP or cyclic GMP, was destroyed by kainic acid injection. Specific binding of [ 3H]etorphine and [ 3H]spiroperidol was reduced by up to 62% in the injected side, while non-specific binding was unchanged. All of these changes were time-dependent, and were greatest 7–14 days after kainic acid treatment. On the other hand, intrastriatal kainic acid injection caused no change in the steady-state concentration of cyclic AMP in striatal slices, or in the in vivo cyclic AMP content in the striatum of rats killed by microwave irradiation. Receptor-mediated increases in cyclic AMP accumulation in striatal slices were either unchanged or markedly potentiated by kainic acid treatment. The maximum response to adenosine was unchanged, while the response to isoprenaline was increased up to 3.7-fold, the response to dopamine increased up to 6.7-fold, and the response to PGE 1 increased up to 30-fold. The effect of dopamine in kainic acid-treated striatal slices was no longer blocked by fluphenazine, but was blocked by propranolol, suggesting an interaction of dopamine with a β-adrenoceptor in kainic acid-treated slices. The results suggest differential cellular localizations of the various receptor-linked cyclic AMP systems in rat neostriatum. Some dopamine and opiate receptors, as well as most of the phosphodiesterase activity, are associated with local neuronal elements, while β-adrenoceptor, adenosine and PGE 1 alterations in cyclic AMP are not. The potentiation of the β-adrenoceptor and PGE 1 responses suggests that they may occur in glial cells. In addition, the pool of adenylate cyclase destroyed by kainic acid appears to make little contribution to normal levels of cyclic AMP in the tissue.

Destruction of post-synaptic dopamine receptors prevents neuroleptic-induced activation of striatal tyrosine hydroxylase but not dopamine synthesis stimulation

Destruction of post-synaptic dopamine (DA)-receptors by intrastriatal kainic acid prevents the haloperidol-induced activation of striatal tyrosine-hydroxylase but not the stimulation of DA-synthesis estimated in vivo on the accumulation of 3,4-dihydroxyphenylalanine (DOPA) after inhibition of aromatic aminoacid decarboxylase. The results indicate the existence of two DA-receptor-mediated mechanisms regulating DA-synthesis in vivo: one depending on the presence of post-synaptic DA-receptors and capable of producing a stable activation of tyrosine-hydroxylase whereas the other is not associated to a persistent conformational change of tyrosine-hydroxylase and is possibly mediated by pre-synaptic DA-receptors. The results also indicate that the activation of striatal tyrosine-hydroxylase by neuroleptics is unrelated to blockade of pre-synaptic DA-receptors.

Loss of striatal dopaminergic receptors after intrastriatal kainic acid injection

Lesioning of the rat striatum with kainic acid may provide a useful animal model with which to study Huntington's Disease since, in both situations, changes in several neurochemical parameters appear similar. In this study, we examined the time course of dopaminergic (DA) and muscarinic cholinergic (MCHOL) receptor alterations after kainic acid injection into the rat striatum. As early as two days after unilateral, intrastriatal injection of kainic acid, most striatal perikaya in the injected area had been destroyed as seen by histological examination. A progressive decrease in the DA and MCHOL receptors continued which was not due to changes in their affinity for their respective receptors. By 48 days after injection, there was about 75% decrease in DA receptors and about a 65% decrease in MCHOL receptors. The DA receptor loss is similar in extent to the reported loss in activity of striatal, dopamine-stimulated adenylate cyclase after kainic acid lesion. The DA and MCHOLreceptor loss is similar to the reported loss of neostriatal DA and MCHOL receptors in Huntington's Disease.

Release of radiolabeled dopamine, serotonin, acetylcholine and GABA from slices of rat striatum after intrastriatal kainic acid injections

Release of radiolabeled dopamine, serotonin, acetylcholine and GABA from slices of rat striatum after intrastriatal kainic acid injections