Spontaneous functional recovery from parkinsonism is not due to reinnervation of the dorsal striatum by residual dopaminergic neurons

Cats exposed to MPTP experience severe motor deficits that spontaneously recover after 4–6 weeks. This recovery occurs despite a persistent deficit (approximately 95%) in dorsal striatal DA levels. To determine whether residual DA neurons that previously did not innervate the dorsal caudate nucleus (CD) have innervated this area in recovered MPTP-treated animals, HRP was injected into the dorsal lateral and dorsal medial CD and the locations of retrogradely labeled neurons in ventral mesencephalon were mapped in normal and recovered MPTP-treated cats. Tyrosine hydroxylase (TH) positive cells were also counted in ventral mesencephalic DA-containing cell groups in normal, symptomatic, and recovered MPTP-treated cats. Results showed no difference in the pattern of HRP labeling in normal and recovered cats except for the loss of labeled substantia-nigra pars compacta (SNc) cells in MPTP-treated cats. Cell counts revealed no significant difference in the degree of TH-positive cell loss in all ventral mesencephalic areas studied in both symptomatic and recovered cats. The results suggest that spontaneous recovery of gross motor function in MPTP-treated cats is most likely not dependent upon reinnervation of the dorsal striatum from residual DAergic neurons.     

Striatal enkephalin gene expression does not reflect parkinsonian signs

Loss of striatal dopamine has been associated with an increase in striatal enkephalin expression. However, the relationship between increased striatal enkephalin expression and the manifestation of parkinsonian motor deficits is not clear. Administration of MPTP to cats produces a severe parkinsonian condition from which the animals spontaneously recover. Using in situ hybridization histochemistry, preproenkephalin (PPE) mRNA expression was examined in the striatum of cats when normal, symptomatic for or spontaneously recovered from MPTP-induced parkinsonism. In all areas of the striatum, PPE mRNA levels were significantly elevated in animals exhibiting severe parkinsonian motor deficits and remained elevated even after recovery of gross motor functioning. These results show that striatal PPE gene expression and parkinsonian motor deficits are not directly correlated.     

Differential regulation of tyrosine hydroxylase in the basal ganglia of mice lacking the dopamine transporter

Mice lacking the dopamine transporter (DAT) display biochemical and behavioural dopaminergic hyperactivity despite dramatic alteration in dopamine homeostasis. In order to determine the anatomical and functional integrity of the dopaminergic system, we examined the expression of tyrosine hydroxylase (TH), the rate-limiting enzyme of dopamine synthesis as well as DOPA decarboxylase and vesicular monoamine transporter. TH-positive neurons in the substantia nigra were only slightly decreased (-27.6 +/- 4.5%), which can not account for the dramatic decreases in the levels of TH and dopamine that we previously observed in the striatum. TH mRNA levels were decreased by 25% in the ventral midbrain with no modification in the ratio of TH mRNA levels per cell. However, TH protein levels were decreased by 90% in the striatum and 35% in the ventral midbrain. In the striatum, many dopaminergic projections had no detectable TH, while few projections maintained regular labelling as demonstrated using electron microscopy. DOPA decarboxylase levels were not modified and vesicular transporter levels were decreased by only 28.7% which suggests that the loss of TH labelling in the striatum is not due to loss of TH projections. Interestingly, we also observed sporadic TH-positive cell bodies using immunohistochemistry and in situ hybridization in the striatum of homozygote mice, and to some extent that of wild-type animals, which raises interesting possibilities as to their potential contribution to the dopamine hyperactivity and volume transmission previously reported in these animals. In conjunction with our previous findings, these results highlight the complex regulatory mechanisms controlling TH expression at the level of mRNA, protein, activity and distribution. The paradoxical hyperdopaminergia in the DAT KO mice despite a marked decrease in TH and dopamine levels suggests a parallel to Parkinson's disease implying that blockade of DAT may be beneficial in this condition.     

Contrasting effects of repeated treatment vs. withdrawal of methamphetamine on tyrosine hydroxylase messenger RNA levels in the ventral tegmental area and substantia nigra zona compacta of the rat brain

We have assessed the effect of repeated treatment with methamphetamine (METH) on the abundance of the messenger ribonucleic acid molecules encoding the enzyme tyrosine hydroxylase (TH) and preprocholecystokinin (PPCCK) in the substantia nigra zona compacta (SNc) and the ventral tegmental area (VTA) by in situ hybridization histochemistry. Rats were injected twice daily with METH (4 mg/kg of body weight) for 6 consecutive days and sacrificed either 5 h or 15 days after the last injection. TH mRNA in the VTA was unaffected by repeated METH treatment but was decreased 25% relative to controls in the SNc. Concurrent administration of METH and MK-801 decreased TH mRNA levels in the SNc to 47% relative to controls. In contrast, TH mRNA levels were found increased in the VTA (42%) but not SNc 15 days post-METH treatment. Coadministration of MK-801 with METH prevented the increase in TH mRNA in the VTA. PPCCK mRNA levels were not significantly affected by METH treatment in VTA or SNc either 5 h or 15 days posttreatment. The results demonstrate that exposure to repeated methamphetamine elicits changes of TH mRNA levels in the VTA that become manifest 2 weeks after withdrawal from this psychostimulant drug. © 1996 Wiley-Liss, Inc.     

Cellular localization of tyrosine hydroxylase mRNA and cholecystokinin mRNA-containing cells in the ventral mesencephalon of the common marmoset: effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine.

In situ hybridization histochemistry was used to localize tyrosine hydroxylase (TH) mRNA and cholecystokinin (CCK) mRNA-expressing cells in the ventral mesencephalon of the common marmoset (Callithrix jacchus) and to examine the effects of the dopaminergic (DA) neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on these two populations of neurons in the pars compacta of the substantia nigra (SNc) and ventral tegmental area (VTA). X-ray film and liquid emulsion autoradiography of brain sections hybridized with an 35S-labelled synthetic 45-mer antisense human TH oligonucleotide probe showed strong hybridization signals and dense populations of TH mRNA expressing cells in the SNc and VTA at all levels, in the control marmoset brain. In the MPTP-treated brain, there was a substantial reduction of TH mRNA in the ventral midbrain. The loss of TH mRNA-expressing cells amounted to 98% in the lateral SNc, 88% in the medial SNc and 33% in the VTA. In situ hybridization of adjacent sections with an 35S-labelled synthetic 45-mer antisense human CCK oligonucleotide probe showed a weak hybridization signal for CCK mRNA in the ventral midbrain of the control brain. Emulsion autoradiography demonstrated CCK mRNA expressing cells in the SNc and VTA at all levels with the number of cells in the VTA similar to that for TH mRNA. However, the number of cells in the SNc expressing CCK mRNA was a fraction (1/4) of that expressing TH mRNA; moreover, the level of expression per cell was substantially less than that for TH mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)     

Nociceptin/orphanin FQ and opioid receptor-like receptor mRNA expression in dopamine systems

Although nociceptin/orphanin FQ (N/OFQ) influences dopamine (DA) neuronal activity, it is not known whether N/OFQ acts directly on DA neurons, indirectly by means of local circuitry, or both. We used two parallel approaches, dual in situ hybridization (ISH) and neurotoxic lesions of DA neurons by using 6-hydroxydopamine (6-OHDA), to ascertain whether N/OFQ and the N/OFQ receptor (NOP) mRNA are expressed in DA neurons in the ventral tegmental area (VTA) and substantia nigra compacta (SNc). In the VTA and SNc, small populations (approximately 6-10%) of N/OFQ-containing neurons coexpressed mRNA for tyrosine hydroxylase (TH), the rate-limiting enzyme for DA synthesis. Similarly, very few (1-2%) TH-positive neurons contained N/OFQ mRNA signal. A majority of NOP-positive neurons (approximately 75%) expressed TH mRNA and roughly half of the TH-containing neurons expressed NOP mRNA. Many N/OFQ neurons (approximately 50-60%) expressed glutamic acid decarboxylase 65 and 67 mRNAs, markers for gamma-aminobutyric acid (GABA) neurons. In the 6-OHDA lesion studies, NOP mRNA levels were nearly 80 and 85% lower in the VTA and SNc, respectively, on the lesioned side. These lesions appear to lead to compensatory changes, with N/OFQ mRNA levels approximately 60% and 300% higher in the VTA and SNc, respectively, after 6-OHDA lesions. Finally, N/OFQ-stimulated [(35)S]guanylyl-5'-O-(gamma-thio)-triphosphate levels were decreased in the VTA and SNc but not the prefrontal cortex after 6-OHDA lesions. Accordingly, it appears that N/OFQ mRNA was found largely on nondopaminergic (i.e., GABA) neurons, whereas NOP mRNA was located on DA neurons. N/OFQ is in a position to influence DA neuronal activity by means of the NOP located on DA neurons.     

6-OHDA诱导大鼠多巴胺神经元选择性缺失的研究

目的 电压依赖性钙离子通道分布对6-羟基多巴胺（6-OHDA）诱导的SD大鼠多巴胺能神经元缺失的影响.方法 6-OHDA单侧脑内内侧前脑束（MFB）立体定位注射,术后10d观测行为学变化;并取脑固定,免疫组化酪氨酸羟化酶（TH）染色观察中脑黑质致密部（SNc）与腹侧背盖区（VTA）多巴胺能神经元的凋亡情况.并应用膜片钳全细胞记录技术,测量SNc与VTA多巴胺能神经元的电压依赖性钙离子通道的电流密度.结果 损伤侧的SNc区TH阳性细胞与对侧比较明显减少,而VTA区TH阳性细胞与对侧相比变化较小;全细胞记录电压膜片钳技术测量,发现SNc多巴胺能神经元钙通道电流密度与VTA相比明显较高.结论 该结果的发现,提示钙离子通道可能参与到帕金森氏病中脑多巴胺能神经元的选择性凋亡的机制.     

Delayed plasticity of the mesolimbic dopamine system following neonatal 6-OHDA lesions

In this study, we determined the ontogenetic profile (at postnatal days 7, 14, 35, and 90) of tyrodine hydroxylase (TH) mRNA in the ventral mesencephalon, and the levels of TH immunoreactivity (TH-IR) and dopamine (DA) transporter (DAT) sites in the striatum of rats that had received intrastriatal 6-hydroxy dopamine (6-OHDA) or vehicle lesions on day of birth (DO) or postnatal day 1 (P1). TH-IR was significantly decreased in all quadrants of the caudate-putamen at all time points, while TH-IR in the nucleus accumbens was unchanged, as compared to controls. Relative to the earliest time point (P7 lesion group), TH-IR recovered significantly in the medial caudate-putamen (CPu) of the P14, P35 and P90 6-OHDA-lesioned groups. Quantitative autoradiography of [³H]-mazindol binding to DAT sites showed significant, lesion-induced losses throughout the caudate-putamen of the 6-OHDA-lesioned groups at all time points and did not show appreciable recovery. Using in situ hybridization, significant (P < .05) decreases in TH mRNA levels were found at all time points in the lateral and medial substantia nigra pars compacta of 6-OHDA-lesioned animals. TH mRNA levels in the rostral ventral tegmental area (VTA), which were significantly decreased at P7, P14 and P35, returned to control levels at P90. TH mRNA levels in the caudal VTA were unchanged through P35 and became significantly elevated as compared to controls (+22%, P < .05) by P90. Thus, recovery of TH-IR in the medial caudate-putamen occurred prior to the elevation in levels of TH mRNA of the VTA. Our findings suggest that compensation exists in early development in certain subpopulations of mesostriatal DA neurons that differs from that in the adult. Synapse 25:293–305, 1997. © 1997 Wiley-Liss, Inc.     

Striatal preprotachykinin gene expression reflects parkinsonian signs

Striatal preprotachykinin (PPT) gene expression was measured in MPTP-treated cats when symptomatic and during various stages of recovery from parkinsonism using in situ hybridization histochemistry. Animals expressing severe (1 week post-MPTP) or moderate (3 weeks post-MPTP) parkinsonian sensorimotor deficits had significantly reduced striatal PPT mRNA expression. In contrast, fully recovered animals (6 weeks post-MPTP) had striatal PPT mRNA levels that were not significantly different from normal. Thus, PPT gene expression in the striatum appears to reflect presence or absence of sensorimotor deficits in MPTP-treated cats.     

Increase of tyrosine hydroxylase and dopamine transporter mRNA levels in ventral tegmental area of male mice under influence of repeated aggression experience.

Tyrosine hydroxylase (TH) and dopamine transporter (DAT) mRNA levels in the ventral tegmental area (VTA) of midbrain were measured by multiplex RT-PCR in male mice with repeated experience of social victories (winners) and social defeats (losers) in 10 daily agonistic confrontations. Two independent experiments revealed enhanced TH and DAT mRNA levels in VTA of the winners in comparison with the losers and controls (animals after 5 days of individual housing). A positive correlation between DAT and TH mRNA levels was shown.     

Effect of 6-hydroxydopamine on striatal GDNF and nigral GFRalpha1 and RET mRNAs in the adult rat

Exogenous GDNF as well as vectors containing the gene for this trophic factor has been shown to be neuroprotective in animal models of Parkinson's disease. We therefore investigated whether changes in striatal GDNF protein and nigral mRNA levels of its co-receptors GFRalpha1 and RET occur in response to lesions of dopamine (DA) neurons and examined the temporal profile of these changes as they relate to the loss of dopaminergic markers. Rats were lesioned with 6-hydroxydopamine and sacrificed 3 h to 60 days post-infusion. DA tissue levels in the striatum and tyrosine hydroxylase immunoreactivity in the substantia nigra (SN) and ventral tegmental area (VTA) were used to determine the size of the lesions. GDNF protein was measured in the striatum using radioimmunocytochemistry. In situ hybridization was used to determine alterations in the mRNAs of RET and GFRalpha1 in the SN and VTA. We observed no persistent changes in GDNF protein in the striatum in response to 6-hydroxydopamine over the 60-day observation period, suggesting that compensatory changes in this trophic factor do not occur in response to injury. Dramatic decreases in RET and GFRalpha1 were observed in both SN and VTA that were generally correlated with the loss of TH protein and striatal DA content, strongly suggesting that these receptors are located on DA neurons and that the protective effect of GDNF reflects a direct action of the trophic factor on these neurons.     

Localization of striatal opioid gene expression,and its modulation by the mesostriatal dopamine pathway: An in situ hybridization study

In situ hybridization was used to study the macroscopic distribution and regulatory control of proenkephalin mRNA and prodynorphin mRNA in rat striatum. While proenkephalin mRNA was widely distributed throughout the striatum, levels of prodynorphin mRNA were highest in the medial and ventral portions of the striatum. Furthermore, in contrast to the results for proenkephalin mRNA, the levels of prodynorphin mRNA appeared higher in the nucleus accumbens than in the striatum. The mesostriatal dopaminergic pathway was destroyed by discrete, unilateral injection of 6-hydroxydopamine (6-OHDA) into either the substantia nigra or the neighboring ventral tegmental area (VTA). Lesions of the substantia nigra caused a dramatic ipsilateral increase in the hybridization signal for proenkephalin mRNA, but no change was observed in the hybridization signal for prodynorphin mRNA. Similar effects were seen with VTA lesions. Since destruction of the mesostriatal dopamine system elevates the levels of proenkephalin mRNA, but not of prodynorphin mRNA, in the striatal target neurons, it appears that the mesostriatal pathway exerts a tonic and selective suppression of striatal proenkephalin gene expression at the mRNA level.     

Intraventricular insulin increases dopamine transporter mRNA in rat VTA/substantia nigra

The hormone insulin can down-regulate the function and synthesis of the re-uptake transporter for norepinephrine (NET) in vivo and in vitro. In the present study we tested whether this action of insulin is generalized to another member of the catecholamine transporter family. We determined the level of dopamine transporter (DAT) mRNA expression in the ventral tegmental area (VTA)/substantia nigra compacta (SNc) of rats which were chronically treated with vehicle or insulin via the third cerebral ventricle (i.c.v.). DAT mRNA was significantly elevated in the VTA/SNc of rats treated with insulin, as compared with levels in vehicle-treated rats. This is in contrast to our previous observation that i.c.v. insulin decreases NET mRNA in the rat locus coeruleus, and suggests that insulin may have differential and specific modulatory effects on CNS catecholaminergic pathways.     

Differences in release and clearance of extracellular dopamine in the striatum after spontaneous or GM1-ganglioside-stimulated recovery from experimental Parkinsonism

PURPOSE: This study was designed to assess differences in dopamine clearance rates and potassium chloride (KCl)-stimulated release in the striatum of cats that had either spontaneously recovered from 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP)-induced Parkinsonism or recovered after receiving GM1 ganglioside treatment. METHODS: A severe Parkinsonian motor disorder was produced in 17 adult cats by administration of MPTP for seven to ten days. Six MPTP-treated cats received daily GM1 administration (30 mg/kg, i.m.) for 6 weeks and eleven MPTP-treated cats were allowed to spontaneously recover over the same period of time. High-speed chronoamperometric electrochemical measurements were obtained from dorsal and ventral striatal regions in all animals. Dopamine clearance rates were obtained by measuring the clearance of pressure-ejected dopamine from the extracellular space and local potassium-induced release was studied by applying KCl to the tissue. RESULTS: Dopamine clearance rates recorded in all striatal areas in GM1-treated cats were significantly faster than dopamine clearance rates recorded in spontaneously recovered cats. In GM1-treated animals, electrochemical signals recorded in response to KCl stimulation were sig-nificantly greater in all striatal areas compared to spontaneously recovered animals. Reduction/oxidation (redox) ratios recorded in GM1- treated animals indicated dopamine to be the predominant electroactive species released in all striatal areas in response to KCl stimulation. Redox ratios recorded in the ventral striatum of spontaneously recovered cats also indicated dopamine to be the predominant electroactive spe-cies released in response to KCl stimulation. However, redox ratios recorded in the dorsal striatum of spontaneosuly recovered cats indicated serotonin to significantly contribute to the recorded signal. CONCLUSIONS: These results support previous observations that volume transmission may predominate dopaminergic signaling in the stria-tum of spontaneously recovered cats and suggest that a greater degree of synaptic transmission is possible in GM1-treated animals. While the functional significance of this partial restoration of dopaminergic synaptic transmission in the striatum remains to be determined, it may under-lie improved behavioral recovery observed following GM1 treatment.     

Effect of pentylenetetrazol on the expression of tyrosine hydroxylase mRNA and norepinephrine and dopamine transporter mRNA

Seizure activity has been shown to have differential effects on the terminal content of the monoamines, norepinephrine (NE) and dopamine (DA). Induction of seizure activity reduces the terminal content of NE, while DA levels remain unchanged or slightly elevated. This study examined the effect of the chemoconvulsant pentylenetetrazol (PTZ) on the mRNA expression of regulatory proteins which maintain the terminal content of NE and DA (i.e., synthesis and re-uptake). The areas examined were the noradrenergic neurons of the locus coeruleus (LC) and dopaminergic neurons of the substantia nigra pars compacta/ventral tegmentum area (SNpc/VTA) in the rat. In the LC, PTZ increased mRNA expression of the immediate early gene, c-fos, and mRNA expression of the synthesizing enzyme, tyrosine hydroxylase (TH), and the re-uptake protein, norepinephrine transporter (NET). This effect on TH and NET was observed only 1 day after the administration of PTZ. In contrast, PTZ did not alter the expression of c-fos mRNA in the SNpc/VTA, but reduced the expression of the dopamine transporter (DAT) mRNA. This effect was observed only 1 day after the administration of PTZ. TH mRNA expression in dopaminergic neurons was elevated initially in a manner similar to that observed in the LC. However, the effect of PTZ on TH mRNA expression in dopaminergic neurons was more prolonged (still elevated 3 days later). These results indicate that the chemoconvulsant PTZ has differential effects on the mRNA expression of regulatory systems (TH and neurotransporter proteins) in noradrenergic and dopaminergic neurons.     

Differential modification of dopamine transporter and tyrosine hydroxylase mRNAs in midbrain of subjects with parkinson's,alzheimer's with parkinsonism,and alzheimer's disease

The molecular characteristics of midbrain dopamine (DA) neurons have been extensively studied in Parkinson's disease (PD). No such studies of the characteristics of midbrain DA neurons in Alzheimer's disease (AD) or Alzheimer's disease with parkinsonism (AD/Park) have been published. We examined the levels of tyrosine hydroxylase (TH) protein, and the expression of TH and dopamine transporter (DAT) mRNAs, in midbrain neurons of PD, AD, and AD/Park cases. In PD, the loss of TH protein in the ventral tier of the substantia nigra pars compacta (SNpc) of the PD group is accompanied by severe losses in the number of neurons that express TH mRNA and DAT mRNA (74% loss). Remaining neurons show a shift to higher concentrations of TH mRNA but a shift to lower concentrations of DAT mRNA per cell. Hence, there is evidence that compensation in the remaining neurons can elevate concentrations of TH mRNA and lower DAT mRNA. Alternatively, there may be a predilection for a loss of neurons with high levels of DAT mRNA and low TH mRNA levels within the SNpc of PD cases. There was no change in TH protein but an elevation of TH mRNA concentrations per neuron without any change in concentrations of DAT mRNA in the AD group. The AD/Park group did not exhibit changes in the level of TH protein, but showed a small loss (26%) of neurons in the SNpc and a greater loss in other regions of the midbrain (43–53%). Remaining DA neurons showed a marked shift to lower concentrations of DAT mRNA per neuron and a nonsignificant shift in cellular concentration of TH mRNA to higher levels. This is consistent with our previous work showing that with AD/Park there is a significant reduction in the number of DAT sites located on DA terminals in the striatum, but the midbrain neurons have not died. Our results indicate that the differential regulation of mRNAs encoding TH and DAT is similar in the parkinsonian disorders (PD and AD/Park) even though the degree of cell death is very different. This might suggest that compensatory events occur in these DA neurons in AD/Park that are similar to those in PD and that result in differential effects on mRNAs encoding TH and DAT proteins.     

Alterations in dopamine uptake sites and D1 and D2 receptors in cats symptomatic for and recovered from experimental parkinsonism

The administration of the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to adult cats severely disrupts the dopaminergic innervation of the striatum. Animals display a parkinson-like syndrome, consisting of akinesia, bradykinesia, postural instability, and rigidity, which spontaneously recovers by 4–6 weeks after the last administration of MPTP. In this study we used quantitative receptor autoradiography to examine changes in DA uptake sites and DA receptors in the basal ganglia of normal, and symptomatic and recovered MPTP-treated cats. Consistent with the destruction of the nigrostriatal DA pathway, there was a severe loss of DA uptake sites, labeled with [³H]-mazindol, in the caudate nucleus (64–82%), nucleus accumbens (44%), putamen (63%), and substantia nigra pars compacta (SNc, 53%) of symptomatic cats. Following behavioral recovery, there were no significant changes in DA uptake site density. Significant increases of [³H]-SCH 23390 binding to D1 DA receptors were observed in the dorsal caudate (>24%; P < 0.05) of symptomatic cats and in all regions of the caudate-putamen (>30%; P < 0.05) of recovered animals. [³H]-SCH 23390 binding in tree substantia nigra pars reticulata was half of that in the striatum and showed no changes in symptomatic or recovered animals. No alterations in the binding of [¹²⁵1]-epidepride to D2 receptors was observed in any region of the striatum in either, symptomatic or recovered animals. [¹²⁵1]-Epidepride binding in the SNc was decreased by >36% (P < 0.05) following MPTP treatment. These data show that cats made parkinsonian by MPTP exposure have a significant decrease in the number of DA reuptake sites throughout the striatum and that recovery of sensorimotor function in these animals is not correlated with an increase in the number of striatal reuptake sites. Behavioral recovery, however, does seem to be correlated with a general elevation of Dl receptors throughout the striatal complex. The present data also show that direct correlations between changes in DA receptor regulation after a large DA depleting lesion and behavioral deficits or recovery from those deficits are difficult and that the relationships between DA receptors/transporters and behavior require further study. © 1995 Wiley-Liss, Inc.     

Dopaminergic neurons expressing calbindin in normal and parkinsonian monkeys.

In cynomolgus monkeys, midbrain neurons immunoreactive (IR) for the calcium-binding protein calbindin D-28k (CaBP) occur principally in the dorsal tier of substantia nigra pars compacta (SNc) and in the ventral tegmental area (VTA), and most of these neurons co-express tyrosine hydroxylase (TH). In monkeys rendered parkinsonian (PD) after MPTP injections, CaBP-IR neurons are much less severely affected than TH-IR neurons in SNc and in VTA, and most spared neurons in SNc/VTA display both CaBP and TH immunoreactivity. These results reveal that, in contrast to the situation in other neurodegenerative diseases, CaBP may be used as a marker for a specific neuronal population that is less prone to degeneration in Parkinson's disease.