Rat Brain Striatal Slices Research Articles

Adenosine A2A receptor blockade attenuates excitotoxicity in rat striatal medium spiny neurons during an ischemic-like insult.

During brain ischemia, excitotoxicity and peri-infarct depolarization injuries occur and cause cerebral tissue damage. Indeed, anoxic depolarization, consisting of massive neuronal depolarization due to the loss of membrane ion gradients, occurs in vivo or in vitro during an energy failure. The neuromodulator adenosine is released in huge amounts during cerebral ischemia and exerts its effects by activating specific metabotropic receptors, namely: A1, A2A, A2B, and A3. The A2A receptor subtype is highly expressed in striatal medium spiny neurons, which are particularly susceptible to ischemic damage. Evidence indicates that the A2A receptors are upregulated in the rat striatum after stroke and the selective antagonist SCH58261 protects from exaggerated glutamate release within the first 4 hours from the insult and alleviates neurological impairment and histological injury in the following 24 hours. We recently added new knowledge to the mechanisms by which the adenosine A2A receptor subtype participates in ischemia-induced neuronal death by performing patch-clamp recordings from medium spiny neurons in rat striatal brain slices exposed to oxygen and glucose deprivation. We demonstrated that the selective block of A2A receptors by SCH58261 significantly reduced ionic imbalance and delayed the anoxic depolarization in medium spiny neurons during oxygen and glucose deprivation and that the mechanism involves voltage-gated K+ channel modulation and a presynaptic inhibition of glutamate release by the A2A receptor antagonist. The present review summarizes the latest findings in the literature about the possibility of developing selective ligands of A2A receptors as advantageous therapeutic tools that may contribute to counteracting neurodegeneration after brain ischemia.

Lack of Autophagy Induction by Lithium Decreases Neuroprotective Effects in the Striatum of Aged Rats

The pharmacological modulation of autophagy is considered a promising neuroprotective strategy. While it has been postulated that lithium regulates this cellular process, the age-related effects have not been fully elucidated. Here, we evaluated lithium-mediated neuroprotective effects in young and aged striatum. After determining the optimal experimental conditions for inducing autophagy in loco with lithium carbonate (Li2CO3), we measured cell viability, reactive oxygen species (ROS) generation and oxygen consumption with rat brain striatal slices from young and aged animals. In the young striatum, Li2CO3 increased tissue viability and decreased ROS generation. These positive effects were accompanied by enhanced levels of LC3-II, LAMP 1, Ambra 1 and Beclin-1 expression. In the aged striatum, Li2CO3 reduced the autophagic flux and increased the basal oxygen consumption rate. Ultrastructural changes in the striatum of aged rats that consumed Li2CO3 for 30 days included electrondense mitochondria with disarranged cristae and reduced normal mitochondria and lysosomes area. Our data show that the striatum from younger animals benefits from lithium-mediated neuroprotection, while the striatum of older rats does not. These findings should be considered when developing neuroprotective strategies involving the induction of autophagy in aging.

Protein Phosphatases but not Reactive Oxygen Species Play Functional Role in Acute Amphetamine-Mediated Dopamine Release

Drug abuse-induced neurodegeneration can be triggered by elevated production of reactive oxygen species (ROS). Involvement of oxidative stress in acute amphetamine (AMPH)-mediated dopamine (DA) release, however, has not been completely understood yet. In order to elucidate the dopaminergic response of PC12 cells to a single dose of 10 μM AMPH, ROS production was measured as related to the extracellular DA level. Due to the spontaneous oxidation of peroxide-sensitive fluorophore 2',7'-dichlorofluorescin diacetate (DCFH-DA) to 2',7'-dichlorofluorescein (DCF), the increase in fluorescence could not be unambiguously attributed to AMPH-triggered ROS production. Based on Amplex Red fluorescence, no ROS production was detected after acute AMPH application. Our data strongly suggest that ROS development was not the main triggering factor for immediate DA release after acute AMPH treatment. On the other hand, AMPH-induced elevation of DA levels in rat brain striatal slices was quenched by the water soluble antioxidant, N-acetylcysteine (NAC) at 10 mM. In this study, we also investigated the contribution of protein phosphatases to the AMPH-induced rat brain striatal dopaminergic response. The experimental protocol, double AMPH challenge was applied for screening the effect of NAC and cantharidin on AMPH-mediated DA release. Here we show that AMPH-mediated DA release increased nearly twofold in striatal rat brain slices pretreated for 30 min with 1000 μM cantharidin, a selective PP1 and PP2A inhibitor. These findings prove the lack of ROS inhibitory action on protein phosphatase activity in acute AMPH-mediated DA efflux.

Dopamine release from rat pheochromocytoma (PC12) cells and rat brain striata induced by a series of straight carbon chain aldehydes with variations in carbon chain length and functional groups

Green odor compounds, a group of 6-carbon (C6) aldehydes and alcohols, are able to enhance dopamine release from pheochromocytoma (PC12) cells, rat brain striatal slices, and brain striata in living rats. In this study, we examined the effects of aldehydes and alcohols with varying carbon chain lengths (2–9 carbons) and functional groups on dopamine release in PC12 cells, brain slices, and living rat brain. In PC12 cells, n-aldehydes and n-alcohols promoted dopamine release, and this effect was stronger as the carbon chain length increased. In rat brain slices, however, the maximum dopamine release was detected when stimulated by n-hexanal, while n-nonanal promoted the lowest level of release. In addition, C6 compounds with a hydroxyl, aldehyde, or carboxyl group enhanced the dopamine release from PC12 cells and striatal slices. In the microdialysis study, n-hexanal and n-hexanol enhanced dopamine release, while n-nonanal promoted lower activity than n-hexanol. The relationship of the concentration of the odor-related compounds and the amount of dopamine released differed between PC12 cells and brain slices. Dopamine release in the living rat brains was similar to that in brain slices. These data suggested that the length of the carbon chain correlated with the strength of dopamine release, and the functional groups further modified it. The distinction between PC12 cells and rat striata might be due to the differences in the cell structure or the target molecules within the cells.

Effects of n-hexanal on dopamine release in the striatum of living rats

Green odor is present in many green leaves, vegetables, and fruits and is composed of four 6-carbon straight-chain alcohols, n-hexanol, (E)-2-hexenol, (Z)-3-hexenol, and (E)-3-hexenol, and four aldehydes, n-hexanal, (E)-2-hexenal, (Z)-3-hexenal, and (E)-3-hexenal. It has been reported that certain green odor compounds enhance dopamine release from rat brain striatal slices and rat pheochromocytoma cells (PC12 cells). It is well known that intracellular Ca2+ levels regulate dopamine release. The amount of dopamine released by n-hexanal-treated PC12 cells decreased in cells pretreated with a membrane-permeable Ca2+ chelator. In this study, the effect of n-hexanal on dopamine release in the brain striatum of living rats was studied using an in vivo brain microdialysis system. Local stimulation with n-hexanal diluted in Ringer's solution to 0.01%, 0.05%, or 0.1% enhanced dopamine release in a concentration-dependent manner. The amount of dopamine released with 0.01% n-hexanal administration significantly declined when either extracellular or intracellular Ca2+ levels decreased. Furthermore, the extracellular dopamine concentration increased with perfusion of nomifensine, an inhibitor of dopamine uptake into cells. When nomifensine was co-perfused with n-hexanal into the striatum, extracellular dopamine release increased further. Accordingly, the concentration of dopamine metabolite and the ratio of dopamine metabolite to dopamine decreased after treatment with n-hexanal. These responses were similar to those seen with KCl stimulation. These data suggest that n-hexanal stimulates dopamine release but does not inhibit dopamine uptake in the brain striatum of living rats, and that dopamine release associated with n-hexanal is regulated by both extracellular and intracellular Ca2+ levels.

Low concentrations of methamidophos do not alter AChE activity but modulate neurotransmitters uptake in hippocampus and striatum in vitro

AimsMethamidophos (Meth) is a toxic organophosphorus compound (OP) that inhibits acetylcholinesterase enzyme (AChE) and induces neurotoxicity. As the mechanism of its neurotoxic effects is not well understood, the aim of the present study was to evaluate the effects of Meth on glutamate and gamma aminobutyric acid (GABA) uptake and correlate with cell viability and AChE and Na+/K+-ATPase enzyme activities in striatum and hippocampus slices exposed to low concentrations (0.05 to 1.0μM) of Meth. Main methodsHippocampal and striatal slices of rat brain were exposed to Meth for 5min ([3H]Glutamate uptake) or 15min ([3H]GABA uptake) for assays. The enzyme activities and cell viability were also accessed at both times in hippocampal and striatal slices and homogenates. Key findingsAt concentrations that did not inhibit AChE, Meth caused changes in glutamate uptake in striatal (0.05 and 1.0μM Meth) and hippocampal (1.0μM Meth) slices. GABA uptake was increased by the pesticide in striatum at 0.5 and 1.0μM and in hippocampus at 0.05μM. After 3.5h of Meth exposure, striatal and hippocampal cells showed no changes in viability as well as no inhibition of Na+/K+-ATPase were observed after 5 or 15min exposure to Meth in the same brain structures. SignificanceResults suggest that Meth, even without changing the AChE activity can modify somehow the neurotransmitters uptake. However, further studies are necessary to clarify if this modulation in glutamate or GABA uptake may be responsible to cause some disturbance in behavior or in other neurochemical parameters following low Meth exposure in vivo.

Adenosine Release Evoked by Short Electrical Stimulations in Striatal Brain Slices Is Primarily Activity Dependent

Adenosine is an important neuromodulator in the brain. Traditionally, adenosine is thought to arise in the extracellular space by either an extracellular mechanism, where it is formed outside the cell by the breakdown of released ATP, or an intracellular mechanism, where adenosine made inside the cell is transported out. Recently, a proposed third mechanism of activity dependent adenosine release has also been proposed. Here, we used fast-scan cyclic voltammetry to compare the time course and mechanism of adenosine formation evoked by either low- or high-frequency stimulations in striatal rat brain slices. Low-frequency stimulations (5 pulses at 10 Hz) resulted in an average adenosine efflux of 0.22 ± 0.02 μM, while high-frequency stimulations (5 pulses, 60 Hz) evoked 0.36 ± 0.04 μM. Blocking intracellular formation by inhibiting adenosine transporters with S-(4-nitrobenzyl)-6-thioinosine (NBTI) or propentofylline did not decrease release for either frequency, indicating that the release was not due to the intracellular mechanism. Blocking extracellular formation with ARL-67156 reduced low-frequency release about 60%, but did not affect high-frequency release. Both low- and high-frequency stimulated release were almost completely blocked by removal of calcium, indicating activity dependence. Reducing dopamine efflux did not affect adenosine release but inhibiting ionotropic glutamate receptors did, indicating that adenosine release is dependent on downstream effects of glutamate. Therefore, adenosine release after short, high-frequency physiological stimulations is independent of transporter activity or ATP metabolism, and may be due to direct release of adenosine after glutamate receptor activation.

Hypericum perforatum L. (St John's wort) extract Ze 117 inhibits dopamine re‐uptake in rat striatal brain slices. An implication for use in smoking cessation treatment?

Classic synthetic antidepressant drugs, as well as St John's wort extract (SJW), directly inhibit the re-uptake of norepinephrine (NE) and/or serotonin (5-HT) into pre-synaptic axons. With chronic treatment they induce adaptive changes in a number of neurotransmitter receptors in synaptic membranes. The immediate effects of SJW Ze 117, an extract low in hyperforin content, on the specific dopamine (DA) uptake were studied in rat striatal brain slices and compared with the effects on NE and 5-HT uptake in rat cortical brain slices. Specific DA uptake was inhibited in a dose dependent manner. In contrast to the findings in synaptosomal preparations published so far, the extract showed different inhibitory potencies for the respective transporters. The potencies for the uptake inhibition of NA, DA and 5-HT were 30, 7 and 1, respectively. The results indicate that the SJW Ze 117 extract interferes in three ways with the individual uptakes of the relevant neurotransmitters that are considered to be causal in the development of depression. This observation, the concomitant and potent inhibition of DA re-uptake by SJW extract, may additionally provide a rationale for the treatment of nicotine or drug addiction with SJW.

The effect of N‐acetylcysteine on amphetamine‐mediated dopamine release in rat brain striatal slices by ion‐pair reversed‐phase high performance liquid chromatography

The amphetamine (AMPH)-induced alteration in rat brain dopamine levels modified by N-acetylcysteine (NAC) administration has been examined using isocratic ion-pair reversed-phase high-performance liquid chromatography with electrochemical detection. The aim of the development of a novel validated evaluation scheme implying a double AMPH challenge was to enhance the efficiency of AMPH-triggered dopamine release measurements in rat brain striatal slices by improving the reproducibility of the results. The proposed experimental protocol was tested in vivo and proved to be capable of fast and reliable drug screening for tracing the effect of NAC as a model compound in AMPH-mediated dopaminergic response. The subcellular localization of the dopamine mobilizing effect of NAC has been established indirectly by the use of an irreversible dopamine vesicular depletor, reserpine. The antioxidant NAC at 10 mM plays an important role in the complete suppression of acute AMPH-elicited dopamine release. The possible role of this quenching effect is discussed.

Effects of direct exposure of green odour components on dopamine release from rat brain striatal slices and PC12 cells

The effects of odour components on dopamine release from rat brain striatal slices and rat pheochromocytoma (PC12) cells were examined. The striatal slices were directly stimulated with 0.5% odour-including Krebs buffer using a superfusion method. In this experiment, (Z)-3-hexenol, (E)-2-hexenal, n-hexanal, 1,8-cineole or Eucalyptus globulus essential oil was used as an odour component. The concentrations of monoamines released in perfusate were measured by HPLC-ECD. Dopamine release from brain slices was significantly enhanced by perfusion of each odour-including solution. In particular, administration of n-hexanal caused a 9-fold increase in dopamine release. The dopamine release by n-hexanal increased linearly with the concentration of n-hexanal up to 0.5% and was maximal at 0.5%. Since PC12 cells have the ability to release dopamine, the effects of four green odour compounds, (Z)-3-hexenol, (E)-2-hexenal, n-hexanal and n-hexanol, on dopamine release were examined. These odour compounds dose dependently increased dopamine release from PC12 cells, and different patterns of dopamine release were observed with aldehyde or alcohol. Odour compounds thus appear to increase dopamine release from dopamine-releasing cells, with differences between aldehydes and alcohols in pattern of release. Dopamine regulates brain functions such as reward, mood, and attention. Green odours may in turn regulate such brain functions through the stimulation of dopamine release.

Dopaminergic differentiation of human neural stem cells mediated by co‐cultured rat striatal brain slices

Properly committed neural stem cells constitute a promising source of cells for transplantation in Parkinson's disease, but a protocol for controlled dopaminergic differentiation is not yet available. To establish a setting for identification of secreted neural compounds promoting dopaminergic differentiation, we co-cultured cells from a human neural forebrain-derived stem cell line (hNS1) with rat striatal brain slices. In brief, coronal slices of neonatal rat striatum were cultured on semiporous membrane inserts placed in six-well trays overlying monolayers of hNS1 cells. After 12 days of co-culture, large numbers of tyrosine hydroxylase (TH)-immunoreactive, catecholaminergic cells could be found underneath individual striatal slices. Cell counting revealed that up to 25.3% (average 16.1%) of the total number of cells in these areas were TH-positive, contrasting a few TH-positive cells (<1%) in non-induced areas. The presence of dopamine in the conditioned culture medium was confirmed by HPLC analysis. Interestingly, not all striatal slice cultures induced TH-expression in underlying hNS1 cells. Common to TH-inductive cultures was, however, the presence of degenerating, necrotic areas, suggesting that factors released during striatal degeneration were responsible for the dopaminergic induction of the hNS1 cells. Ongoing experiments aim to identify such factors by comparing protein profiles of media conditioned by degenerating (necrotic) versus healthy striatal slice cultures.

Nicotinic-receptor potentiator drugs, huprine X and galantamine, increase ACh release by blocking AChE activity but not acting on nicotinic receptors

The main goal of the present study was to analyse the effects of (±)-huprine X ((±)-HX) and galantamine (GAL), with potentiating action on nicotinic receptors, and huperzine A (HPA), devoid of nicotinic activity, on [ 3H]-acetylcholine ([ 3H]-ACh) release in striatal slices of rat brain. All compounds are non-covalent and reversible inhibitors of AChE. Addition of (±)-HX (0.01 μM), GAL (10 μM) and HPA (0.1 μM) to the superfusion medium decreased the release of the ACh neurotransmitter to a similar extent: 36%, 30% and 34%, respectively ( P < 0.01). This effect was reverted in the presence of atropine (ATR; 0.1 μM), which blocks the pre-synaptic muscarinic M 2 receptor. After that, a wide range of concentrations of drugs, concomitantly with ATR (0.1 μM), was studied in the presence of haloperidol (HAL; 0.01μM), a dopamine D 2 antagonist. In these conditions, a dose-dependent increase of [ 3H]-ACh release was observed in the presence of (±)-HX, GAL and HPA. To test the role of nicotinic receptors in the drugs' effects on [ 3H]-ACh release, mecamylamine (MEC) 100 μM was used to block such receptors. MEC alone significantly decreased neurotransmitter release by 18% ( P < 0.05), but no change was obtained in the presence of both ATR and MEC. Under these conditions, (±)-HX, GAL and HPA increased the release of [ 3H]-ACh by 37%, 25% and 38%, respectively ( P < 0.01). Taking into account all of these data, the present results suggest that the effects induced by (±)-HX and GAL nicotinic-receptor potentiators seem to be mainly due to their ability in inhibiting acetylcholinesterase activity, but not by interaction on the nicotinic receptors.

The control of [ 125I]BDNF release from striatal rat brain slices

The depolarisation-induced release of brain-derived neurotrophic factor (BDNF) from adult rat striatal slices was studied in vitro. The slices were preloaded with [ 125I]BDNF and exposed to depolarising stimulation with varying concentrations of veratrine (up to 50 μM) and potassium (up to 50 mM) which caused activity-dependent short-term release of [ 125I]BDNF. The results indicate that this stimulated release of [ 125I]BDNF is not regulated by a feedback mechanism mediated via the TrkB receptor. The release of [ 125I]BDNF was found to be dependent on the concentrations of both extracellular and intracellular calcium, since BDNF release was modulated by the addition of both EGTA and BAPTA-AM, agents chelating either external or internal Ca 2+, respectively. BDNF release also proved to be dependent on activation of IP 3 mediated Ca 2+ release from intracellular stores. [ 125I]BDNF release was also modulated by 5HT 3 receptor ligands and by receptors coupled to adenylate cyclase. Taken together, these results indicate that [ 125I]BDNF release is activity dependent, and is modulated by changes in Ca 2+ levels. Moreover the release occurs via a mechanism involving cAMP.

Adenosine A 2A receptors inhibit the N-methyl- d-aspartate component of excitatory synaptic currents in rat striatal neurons

The effects of the adenosine A 2A receptor agonist 2- p-(2-carboxyethyl)phenethyl-amino-5′- N-ethylcarboxamidoadenosine (CGS 21680) on currents mediated by excitatory amino acid receptors were examined in rat striatal brain slices. In a Mg 2+-free superfusion medium, CGS 21680 decreased the amplitude of excitatory postsynaptic currents (EPSCs) in about 70% of striatal neurons. The inhibitory effect of CGS 21680 disappeared both in the presence of the adenosine A 2A receptor antagonist 8-(3-chlorostyryl) caffeine and the NMDA receptor antagonist 2-amino-5-phosphonopentanoic acid (AP-5). NMDA-induced currents were also depressed by CGS 21680 in a subset of striatal cells, whereas α-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)-induced currents were not affected. The results suggest that adenosine A 2A receptor agonists inhibit the NMDA component of the EPSC.

Modulation of neurotransmitter release induced by brain-derived neurotrophic factor in rat brain striatal slices in vitro

This study examined the influence of brain-derived neurotrophic factor (BDNF) on the basal and depolarisation-induced release of the neurotransmitters GABA, dopamine and serotonin from rat striatal brain slices in vitro. BDNF potentiated the potassium or veratrine-stimulated release of GABA, dopamine and serotonin. This potentiation was shown to be dependent on activation of the high-affinity tyrosine kinase-linked receptor TrkB, as K252a (a potent TrkB antagonist) largely prevented the effects. BDNF potentiated the release of each neurotransmitter to similar extents irrespective of the type of depolarising stimulus used. In all cases the potentiation of neurotransmitter release caused by BDNF was dependent on membrane depolarisation as BDNF alone was incapable of causing potentiation. These results, obtained using striatal slices in vitro, suggest that BDNF may be acting via the specific receptor TrkB to modulate synaptic performance in the corpus striatum in vivo.

Barbiturates inhibit K +-evoked noradrenaline and dopamine release from rat striatal slices – involvement of voltage sensitive Ca 2+ channels

The cellular target site(s) for anaesthetic action remain unclear. In rat striatal slices we have previously demonstrated that K +-evoked noradrenaline (NA) and dopamine (DA) release is mediated predominantly via P/Q-type voltage sensitive Ca 2+ channels (VSCC). Using this model of Ca 2+ dependent transmitter release we have evaluated the effects of anaesthetic and non-anaesthetic barbiturates. Rat brain striatal slices were incubated in the absence and presence of barbiturate for 10 min at 37°C. The slices were then incubated for 6 min with 40 mM KCl. All anaesthetic barbiturates produced a concentration-dependent inhibition of K +-evoked NA and DA release. Non-anaesthetic barbiturate, barbituric acid was ineffective. The pIC 50 for NA and DA release (thiopental: 4.90±0.13 and 5.00±0.10, pentobarbital: 4.39±0.07 and 4.43±0.14, phenobarbital: 3.85±0.08 and 3.59±0.10, respectively) correlated with lipid solubility (NA: r 2=0.999, DA: r 2=0.987). We therefore suggest that barbiturates inhibit catecholamine release via an interaction with P/Q VSCC further implicating this channel in anaesthetic action.

Effect of amphetamine-induced dopamine release on radiotracer binding to D1 and D2 receptors in rat brain striatal slices.

The in vivo binding of positron emission tomography (PET) and single photon emission computer tomography (SPECT) radiotracers to dopamine D2 receptors in the striatum can be influenced by competition with endogenous dopamine. The present study was undertaken to determine if a similar inhibition of radiotracer binding to dopamine receptors could be observed following pharmacologically-evoked dopamine release in rat brain striatal slices. Striatal slices were incubated in a large volume of oxygenated Krebs saline and exposed to amphetamine or methamphetamine to evoke dopamine release within the slice. Amphetamine and methamphetamine, at concentrations up to 30 microM, reduced [3H]raclopride binding in the slices by 77% and 86%, respectively, with 50% inhibition at 1.6 microM amphetamine or 3.0 microM methamphetamine. Neither drug produced a significant effect on binding of [3H]SCH 23390 in the slices. This suggests that dopamine was able to interfere with radiotracer binding to D2 but not D1 receptors. The dopamine uptake blockers, cocaine and methylphenidate, had relatively little effect by themselves on [3H]raclopride binding but, by inhibiting amphetamine-induced dopamine release, significantly reduced inhibition of [3H]raclopride binding by a low (3 microM) amphetamine concentration. At a higher (30 microM) amphetamine concentration the inhibition of [3H]raclopride binding was not antagonized by uptake blockers and data obtained from homogenate binding experiments indicated a direct displacement of [3H]raclopride binding by amphetamine at this concentration. In conclusion the data obtained in the present study demonstrate that the effects of amphetamine on striatal radiotracer accumulation observed in PET and SPECT can also be observed in brain slices in vitro and, at least at low amphetamine concentrations, are mediated by competition with released dopamine.

Inhibition by adenosine A(2A) receptors of NMDA but not AMPA currents in rat neostriatal neurons.

Whole-cell patch clamp experiments were used to investigate the transduction mechanism of adenosine A(2A) receptors in modulating N-methyl-D-aspartate (NMDA)-induced currents in rat striatal brain slices. The A(2A) receptor agonist 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamidoadenosine (CGS 21680) inhibited the NMDA, but not the (S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) current in a subset of striatal neurons. Lucifer yellow-filled pipettes in combination with immunostaining of A(2A) receptors were used to identify CGS 21680-sensitive cells as typical medium spiny striatal neurons. Dibutyryl cyclic AMP and the protein kinase A activator Sp-cyclic AMPs, but not the protein kinase A inhibitors Rp-cyclic AMPS or PKI(14 - 24)amide abolished the inhibitory effect of CGS 21680. The phospholipase C inhibitor U-73122, but not the inactive structural analogue U-73343 also interfered with CGS 21680. The activation of protein kinase C by phorbol 12-myristate 13-acetate or the blockade of this enzyme by staurosporine did not alter the effect of CGS 21680. Heparin, an antagonist of inositol 1, 4,5-trisphosphate (InsP(3)) and a more efficient buffering of intracellular Ca(2+) by BAPTA instead of EGTA in the pipette solution, abolished the CGS 21680-induced inhibition. The calmodulin antagonist W-7 and cytochalasin B which enhances actin depolymerization also prevented the effect of CGS 21680; the calmodulin kinase II inhibitors CaM kinase II(281 - 309) and KN-93 but not the inactive structural analogue KN-92 were also effective. The calcineurin inhibitor deltamethrin did not interfere with CGS 21680. It is suggested that the transduction mechanism of A(2A) receptors to inhibit NMDA receptor channels is the phospholipase C/InsP(3)/calmodulin and calmodulin kinase II pathway. The adenylate cyclase/protein kinase A and phospholipase C/protein kinase C pathways do not appear to be involved.

Correlating physiology with gene expression in striatal cholinergic neurones.

The expression of 34 transmitter-related genes has been examined in the cholinergic neurones of rat striatal brain slices, with the aim of correlating gene expression with functional activity. The mRNAs encoding types I, II/IIA, and III alpha subunits of the voltage-sensitive sodium channels were detected, suggesting the presence of these three types of sodium channel. Similarly, mRNAs encoding all four alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)-type glutamate receptor subunits and the NR1 and NR2A, 2B, and 2D subunits of the NMDA-type glutamate receptors were detected, suggesting that various combinations of these subunits mediate the cellular response to synaptically released glutamate. Other mRNAs detected included the NK1 and NK3 tachykinin receptors, all four known adenosine receptors, and the GABA-synthesising enzyme glutamate decarboxylase. Subpopulations of these cholinergic neurones have been identified on the basis of the expression of the NK3 tachykinin receptor in 5% and the trkC neurotrophin receptor in 12% of the cells investigated.

P1E108 - Neurotoxic effect of Na 2S, a soluble salt of hydrogen sulphide, on striatal slices of rat brain

P1E108 - Neurotoxic effect of Na 2S, a soluble salt of hydrogen sulphide, on striatal slices of rat brain