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The effect of the non-selective nitric oxide synthase inhibitor L-name on rotational behaviour and dopamine metabolism in 6-OHDA-lesioned rats treated chronically with L-DOPA
Abstracts / Nitric Oxide 27 (2012) S2–S50
nitrate/nitrite and S-nitrose compounds, NOx) were evaluated in the striatum of adult rats. NOS isoforms mRNA did not modify the expression in any hypoxic group vs. control. However, quantification of immunoreaction revealed a decrease in eNOS and nNOS after hypoxia. NOx levels as well as NADPH-diaphorase activity, detected in some striatal neurons, significantly diminished throughout the reoxygenation period. These results reflect that NOS isoforms protein expression, in situ NOS activity, and NO concentration decreased after acute HH/reoxygenation in rat striatum, proposing that the NO pathway is altered during such situations in this basal ganglion of the brain. http://dx.doi.org/10.1016/j.niox.2012.04.066
P-9 Involvement of NO in NMDA receptor-independent long-term potentiation Beatrice Pigott, John Garthwaite The Wolfson Institute for Biomedical Research, University College London, London, UK Long-term potentiation (LTP) is a persistent increase in synaptic efficacy and, throughout the brain, a putative model of processes underlying learning and memory. Multiple forms of LTP exist with different dependences on NMDA receptor activation. Since nNOS is thought to be preferentially activated by NMDA receptor channelopening, the role of NO in NMDA receptor-dependent LTP has attracted much attention. In contrast, less is known about the contribution of NO to NMDA receptor-independent LTP. At hippocampal CA3–CA1 synapses, a component of 200 Hz stimulation-induced LTP is resistant to NMDA receptor antagonism but reduced by L-type voltage-gated Ca2+ channel (L-VGCC) inhibition. Since this component (called here L-VGCC-dependent LTP) shares properties with NO-dependent LTP, we tested the involvement of NO in it. Using field potential recording in hippocampal slices pre-incubated with the NMDA antagonist, D-AP5 (100 lM), we found that the L-VGCCdependent LTP could be inhibited by NOS antagonism (100 lM LNNA). The time-course of the inhibition was similar to the reduction caused by the L-VGCC inhibitor, nifedipine (30 lM), and could be mimicked by the NO-targeted guanylyl cyclase antagonist, ODQ (10 lM), suggesting that the NO signal involved was transduced by cGMP. The results of experiments on slices from eNOS-deficient mice, together with the lack of iNOS in hippocampal slices, suggested that nNOS was the sole source of the NO required. These data extend an essential role for neuron-derived NO from NMDA receptor-dependent to NMDA receptor-independent LTP and suggest that some forms of LTP necessitate a currently unknown mechanism for nNOS activation. http://dx.doi.org/10.1016/j.niox.2012.04.067
P-10 The effect of the non-selective nitric oxide synthase inhibitor Lname on rotational behaviour and dopamine metabolism in 6OHDA-lesioned rats treated chronically with L-DOPA Anna Czarnecka, Tomasz Lenda, Jolanta Konieczny, Elzbieta LorencKoci Institute of Pharmacology, Polish Academy of Sciences, Department of Neuropsychopharmacology, Kraków, Poland The strong evidence obtained from in vivo and ex-vivo studies suggests an interaction between the dopaminergic and nitrergic systems.
S19
The aim of this study was to assess whether the inhibition of nitric oxide synthesis in 6-OHDA-lesioned rats treated chronically with L-DOPA affects rotational behaviour and dopamine (DA) metabolism. Male Wistar rats were injected unilaterally with a single dose of 6-OHDA (8 lg/4 ll) into the left medial forebrain bundle. After two weeks, only rats exhibiting a substantial loss of nigrostriatal neurons were treated chronically with L-DOPA (25 mg/kg) once daily for 15 days. On day 14, the rats received single doses of L-NAME (50 or 100 mg/kg) ten minutes before L-DOPA injection, and rotational behaviour was recorded for more than 2 h. On the following day, 1 h after the last injections of L-NAME and L-DOPA, animals were killed. The levels of dopamine (DA) and its metabolites (DOPAC, HVA) were assayed in striatal and nigral homogenates using an HPLC method. A single dose of L-NAME (50 mg/kg), administered before the penultimate dose of L-DOPA, caused contralateral rotations whose intensity was lower than that produced by L-DOPA alone. Moreover, such a combined treatment decreased striatal and nigral DA, DOPAC and HVA levels on the lesioned side compared to administration of L-DOPA alone. On the contralateral side, decreases in the content of DA metabolites only were observed. The higher dose of L-NAME produced weaker effects. Our biochemical results suggest that L-NAME prevents DA formation from L-DOPA, which eventually leads to attenuation of the LDOPA-induced rotations. http://dx.doi.org/10.1016/j.niox.2012.04.068
P-11 The influence of the selective NNOS inhibitor 7-nitroindazole on rotational behaviour and dopamine metabolism in 6-OHDAlesioned rats treated chronically with L-DOPA Elzbieta Lorenc-Koci, Anna Czarnecka, Tomasz Lenda, Jolanta Konieczny Institute of Pharmacology, Polish Academy of Sciences, Department of Neuropsychopharmacology, Kraków, Poland Our study was aimed at assessing behavioral and biochemical effects of the selective nNOS inhibitor 7-nitroindazole (7-NI), administered to 6-OHDA-lesioned rats receiving chronically L-DOPA. Male Wistar rats were injected unilaterally with a single dose of 6-OHDA (8 lg/4 ll) into the left medial forebrain bundle. After two weeks, only rats exhibiting a substantial loss of nigrostriatal dopamine (DA) neurons were treated chronically with L-DOPA (25 mg/ kg i.p) once daily for 15 days. On day 14, animals received single doses of 7-NI (30 or 50 mg/kg) ten minutes before L-DOPA injection, and the intensity of rotations was measured until their expiry. On the following day, 1 h or 3 h after the last injections of 7-NI and LDOPA, rats were killed. The levels of DA and its metabolites (DOPAC, HVA) were assayed in striatal and nigral homogenates using an HPLC method. Both single doses of 7-NI, administered before the penultimate dose of L-DOPA, caused contralateral rotations whose intensity was lower, but duration twice as long as that produced by L-DOPA alone. Such a combined treatment significantly increased DA levels in the ipsi- and contralateral striata and substantia nigra, but decreased the concentrations of DOPAC and HVA. The prolonged duration of rotations after the combined treatment seems to be a consequence of a more pronounced increase in DA level in the nigrostriatal DA system than that after L-dopa alone. Since 7-NI decreases the level of monoaminooxidase metabolite,
nitrate/nitrite and S-nitrose compounds, NOx) were evaluated in the striatum of adult rats. NOS isoforms mRNA did not modify the expression in any hypoxic group vs. control. However, quantification of immunoreaction revealed a decrease in eNOS and nNOS after hypoxia. NOx levels as well as NADPH-diaphorase activity, detected in some striatal neurons, significantly diminished throughout the reoxygenation period. These results reflect that NOS isoforms protein expression, in situ NOS activity, and NO concentration decreased after acute HH/reoxygenation in rat striatum, proposing that the NO pathway is altered during such situations in this basal ganglion of the brain. http://dx.doi.org/10.1016/j.niox.2012.04.066
P-9 Involvement of NO in NMDA receptor-independent long-term potentiation Beatrice Pigott, John Garthwaite The Wolfson Institute for Biomedical Research, University College London, London, UK Long-term potentiation (LTP) is a persistent increase in synaptic efficacy and, throughout the brain, a putative model of processes underlying learning and memory. Multiple forms of LTP exist with different dependences on NMDA receptor activation. Since nNOS is thought to be preferentially activated by NMDA receptor channelopening, the role of NO in NMDA receptor-dependent LTP has attracted much attention. In contrast, less is known about the contribution of NO to NMDA receptor-independent LTP. At hippocampal CA3–CA1 synapses, a component of 200 Hz stimulation-induced LTP is resistant to NMDA receptor antagonism but reduced by L-type voltage-gated Ca2+ channel (L-VGCC) inhibition. Since this component (called here L-VGCC-dependent LTP) shares properties with NO-dependent LTP, we tested the involvement of NO in it. Using field potential recording in hippocampal slices pre-incubated with the NMDA antagonist, D-AP5 (100 lM), we found that the L-VGCCdependent LTP could be inhibited by NOS antagonism (100 lM LNNA). The time-course of the inhibition was similar to the reduction caused by the L-VGCC inhibitor, nifedipine (30 lM), and could be mimicked by the NO-targeted guanylyl cyclase antagonist, ODQ (10 lM), suggesting that the NO signal involved was transduced by cGMP. The results of experiments on slices from eNOS-deficient mice, together with the lack of iNOS in hippocampal slices, suggested that nNOS was the sole source of the NO required. These data extend an essential role for neuron-derived NO from NMDA receptor-dependent to NMDA receptor-independent LTP and suggest that some forms of LTP necessitate a currently unknown mechanism for nNOS activation. http://dx.doi.org/10.1016/j.niox.2012.04.067
P-10 The effect of the non-selective nitric oxide synthase inhibitor Lname on rotational behaviour and dopamine metabolism in 6OHDA-lesioned rats treated chronically with L-DOPA Anna Czarnecka, Tomasz Lenda, Jolanta Konieczny, Elzbieta LorencKoci Institute of Pharmacology, Polish Academy of Sciences, Department of Neuropsychopharmacology, Kraków, Poland The strong evidence obtained from in vivo and ex-vivo studies suggests an interaction between the dopaminergic and nitrergic systems.
S19
The aim of this study was to assess whether the inhibition of nitric oxide synthesis in 6-OHDA-lesioned rats treated chronically with L-DOPA affects rotational behaviour and dopamine (DA) metabolism. Male Wistar rats were injected unilaterally with a single dose of 6-OHDA (8 lg/4 ll) into the left medial forebrain bundle. After two weeks, only rats exhibiting a substantial loss of nigrostriatal neurons were treated chronically with L-DOPA (25 mg/kg) once daily for 15 days. On day 14, the rats received single doses of L-NAME (50 or 100 mg/kg) ten minutes before L-DOPA injection, and rotational behaviour was recorded for more than 2 h. On the following day, 1 h after the last injections of L-NAME and L-DOPA, animals were killed. The levels of dopamine (DA) and its metabolites (DOPAC, HVA) were assayed in striatal and nigral homogenates using an HPLC method. A single dose of L-NAME (50 mg/kg), administered before the penultimate dose of L-DOPA, caused contralateral rotations whose intensity was lower than that produced by L-DOPA alone. Moreover, such a combined treatment decreased striatal and nigral DA, DOPAC and HVA levels on the lesioned side compared to administration of L-DOPA alone. On the contralateral side, decreases in the content of DA metabolites only were observed. The higher dose of L-NAME produced weaker effects. Our biochemical results suggest that L-NAME prevents DA formation from L-DOPA, which eventually leads to attenuation of the LDOPA-induced rotations. http://dx.doi.org/10.1016/j.niox.2012.04.068
P-11 The influence of the selective NNOS inhibitor 7-nitroindazole on rotational behaviour and dopamine metabolism in 6-OHDAlesioned rats treated chronically with L-DOPA Elzbieta Lorenc-Koci, Anna Czarnecka, Tomasz Lenda, Jolanta Konieczny Institute of Pharmacology, Polish Academy of Sciences, Department of Neuropsychopharmacology, Kraków, Poland Our study was aimed at assessing behavioral and biochemical effects of the selective nNOS inhibitor 7-nitroindazole (7-NI), administered to 6-OHDA-lesioned rats receiving chronically L-DOPA. Male Wistar rats were injected unilaterally with a single dose of 6-OHDA (8 lg/4 ll) into the left medial forebrain bundle. After two weeks, only rats exhibiting a substantial loss of nigrostriatal dopamine (DA) neurons were treated chronically with L-DOPA (25 mg/ kg i.p) once daily for 15 days. On day 14, animals received single doses of 7-NI (30 or 50 mg/kg) ten minutes before L-DOPA injection, and the intensity of rotations was measured until their expiry. On the following day, 1 h or 3 h after the last injections of 7-NI and LDOPA, rats were killed. The levels of DA and its metabolites (DOPAC, HVA) were assayed in striatal and nigral homogenates using an HPLC method. Both single doses of 7-NI, administered before the penultimate dose of L-DOPA, caused contralateral rotations whose intensity was lower, but duration twice as long as that produced by L-DOPA alone. Such a combined treatment significantly increased DA levels in the ipsi- and contralateral striata and substantia nigra, but decreased the concentrations of DOPAC and HVA. The prolonged duration of rotations after the combined treatment seems to be a consequence of a more pronounced increase in DA level in the nigrostriatal DA system than that after L-dopa alone. Since 7-NI decreases the level of monoaminooxidase metabolite,