Haloperidol-induced synaptic changes in striatum are associated with glutamate synapses
ABSTRACT Sub-chronic treatment with the typical neuroleptic, haloperidol (0.5 mg/kg/d, s.c.), but not the atypical neuroleptic, clozapine (35 mg/kg/day, s.c.), causes an increase in synapses containing a perforated postsynaptic density (referred to as 'perforated' synapses) and in dopamine (DA) D2 receptors within the caudate nucleus . To determine if these perforated synapses are glutamatergic, we systemically co-administered MK-801 (0.3 mg/kg/day for 2 weeks), a non-competitive antagonist at the N-methyl-D-aspartate (NMDA) receptor-associated ion channel, and haloperidol. MK-801 blocked the haloperidol-induced increase in striatal perforated synapses, but not the haloperidol-induced increase in DA D2 receptors. Injection of MK-801 into the striatum also attenuated the haloperidol-induced increase in perforated synapses. Post-embedding immuno-gold electron microscopy using antibodies to glutamate indicated that the gold particles were localized within striatal presynaptic nerve terminals that make contact with perforated postsynaptic densities. These findings support the hypothesis that the haloperidol-induced increase in perforated synapses is regulated by the NMDA subtype of excitatory glutamate receptor. The increase in perforated synapses following administration of haloperidol, which is associated with a high incidence of extrapyramidal side effects (EPS), and the lack of a synaptic change following administration of clozapine, known to have a low frequency of EPS, suggests that glutamate synapses play a role in the motoric side effects that are observed with typical neuroleptic drug treatment.
- SourceAvailable from: Giselle Petzinger
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- "The differences between the experimental groups were analyzed using the Student's t-test. The specificity of the immunolabeling for the glutamate antibody was previously established by incubating the antibody overnight with 3 mM glutamate (Meshul et al., 1994). This mixture was then applied to the sections as detailed above, with the final results showing a lack of tissue immunolabeling. "
ABSTRACT: The goal of this study was to determine whether there was a difference in glutamate within the dorsolateral striatum in mice exhibiting either a high (HR) or low (LR) locomotor response to a novel environment. The number of line crossings over a 30-min-period when the mice were placed in a novel environment was determined, and those mice for which the values were above the mean were in the HR group and those with the values below the mean were in the LR group. In vivo microdialysis was carried out to determine the basal extracellular level of striatal glutamate, and the contralateral striatum was taken to measure the density of glutamate immunolabeling within nerve terminals making an asymmetrical (excitatory) synaptic contact using quantitative immuno-gold electron microscopy. There was a statistically significant difference (35%) in the basal extracellular level of striatal glutamate between the HR and LR groups, with the HR group having a lower level, compared with that of the LR group. There was a 25% difference in the density of nerve terminal glutamate immuno-gold labeling associated with the synaptic vesicle pool in the HR, compared with that in the LR group, but this difference was not statistically significant. There was no change in the basal extracellular level of striatal dopamine between the two groups, but there was a statistically significant difference (73%) in the basal turnover ratio of striatal dopamine and its metabolites in the HR, compared with that in the LR group. The data suggests that the difference in extracellular striatal glutamate between the HR and LR groups is not due to an alteration in basal extracellular dopamine but could be due to an increase in dopamine turnover.Synapse 12/2005; 58(3):200-7. DOI:10.1002/syn.20198 · 2.43 Impact Factor
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- "The differences between treatment groups were analyzed using a one-way ANOVA and significant main effects were further characterized using the Fisher post-hoc test for comparison of multiple means. The specificity of the immunolabeling for the glutamate antibody was previously established by incubating the antibody overnight with 3 mM glutamate (Meshul et al., 1994). This mixture was then applied to the sections as detailed above. "
ABSTRACT: A unilateral lesion of the rat nigrostriatal pathway with 6-hydroxydopamine (6-OHDA) results in a decrease in the basal extracellular level of striatal glutamate, a nearly complete loss of tyrosine hydroxylase (TH) immunolabeling, an increase in the density of glutamate immunogold labeling within nerve terminals making an asymmetrical synaptic contact, and an increase in the number of apomorphine-induced contralateral rotations. [Meshul et al. (1999) Neuroscience 88:1-16; Meshul and Allen (2000) Synapse 36:129-142]. In Parkinson's disease, a lesion of either the subthalamic nucleus (STN) or the motor thalamic nucleus relieves the patient of some of the motor difficulties associated with this disorder. In this rodent model, either the STN or motor thalamic nucleus was electrolytically destroyed 2 months following a unilateral 6-OHDA lesions. Following a lesion of either the STN or motor thalamic nucleus in 6-OHDA-treated rats, there was a significant decrease (40-60%) in the number of apomorphine-induced contralateral rotations compared to the 6-OHDA group. There was a significant decrease (<30%) in the basal extracellular level of striatal glutamate in all of the experimental groups compared to the sham group. Following an STN and/or 6-OHDA lesion, the decrease in striatal extracellular levels was inversely associated with an increase in the density of nerve terminal glutamate immunolabeling. There was no change in nerve terminal glutamate immunogold labeling in either the motor thalamic or motor thalamic plus 6-OHDA lesion groups compared to the sham group. The decrease in the number of apomorphine-induced rotations was not due to an increase in TH immunolabeling (i.e., sprouting) within the denervated striatum. This suggests that alterations in striatal glutamate appear not to be directly involved in the STN or motor thalamic lesion-induced reduction in contralateral rotations.Synapse 03/2004; 51(4):287-98. DOI:10.1002/syn.10306 · 2.43 Impact Factor
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- "The specificity of the immunolabeling for the glutamate antibody was previously established by incubating the antibody overnight with 3 mM glutamate (Meshul et al., 1994). This mixture was then applied to the sections as detailed above, with the final results showing a lack of tissue immunolabeling. "
ABSTRACT: We previously reported that 1 month following unilateral loss (>95%) of striatal dopamine, there is an increase in striatal glutamate function as measured by in vivo microdialysis and quantitative immuno-gold electron microscopy, Neuroscience 88, 1-16). The goal of this study was to determine the effect of bilateral loss of striatal dopamine on striatal glutamate function following acute or subchronic administration of the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to C57/B6J mice. Animals were administered either single injections (ip) of 30 mg/kg/day for 7 days (subchronically treated group) or 20 mg/kg x 4 doses every 2 h (acutely treated group) of the toxin or saline. One month following the first injection, there was a 44 and 65% loss in the relative density of tyrosine hydroxylase (TH) immunolabeling within the dorsolateral striatum in the subchronically and acutely MPTP-treated groups compared to the saline group, respectively. There was a decrease in the basal level of extracellular glutamate within the striatum in the subchronically MPTP-treated animals compared to an increase in the acutely treated group in relationship to the saline group. Ultrastructurally, only in the acutely MPTP-treated group was there a decrease in the density of glutamate immunolabeling within nerve terminals associated with an asymmetrical synaptic contact in the dorsolateral striatum compared to either the subchronic or saline groups. In addition, there was a decrease in the relative density of GluR-2/3 subunit immunolabeling within the dorsolateral striatum in the acute MPTP compared to the saline group. These data indicate that differences in striatal glutamate function appear to be associated with the dosing interval of MPTP administration and the variable loss of striatal TH immunolabeling.Experimental Neurology 04/2003; 180(1):74-87. DOI:10.1016/S0014-4886(02)00050-X · 4.62 Impact Factor