Verbascoside promotes the regeneration of tyrosine hydroxylase-immunoreactive neurons in the substantia nigra

Tyrosine hydroxylase is a key enzyme in dopamine biosynthesis. Change in tyrosine hydroxylase expression in the nigrostriatal system is closely related to the occurrence and development of Parkinson＇s disease. Verbascoside, an extract from Radix Rehmanniae Praeparata has been shown to be clinically effective in treating Parkinson＇s disease. However, the underlying mechanisms remain unclear. It is hypothesized that the effects of verbascoside on Parkinson＇s disease are related to tyrosine hydroxylase expression change in the nigrostriatal system. Rat models of Parkinson＇s disease were established and verbascoside（60 mg/kg） was administered intraperitoneally once a day. After 6 weeks of verbascoside treatment, rat rotational behavior was alleviated; tyrosine hydroxylase m RNA and protein expression and the number of tyrosine hydroxylase-immunoreactive neurons in the rat right substantia nigra were significantly higher than the Parkinson＇s model group. These findings suggest that the mechanism by which verbascoside treats Parkinson＇s disease is related to the regeneration of tyrosine hydroxylase-immunoreactive neurons in the substantia nigra.

Dark rearing maintains tyrosine hydroxylase expression in retinal amacrine cells following optic nerve transection

The present study examined changes in retinal tyrosine hydroxylase （TH） expression in rats having undergone optic nerve transection and housed under a normal day/night cycle or in the dark. The aim was to investigate the effects of amacrine cells on axonal regeneration in retinal ganglion cells and on the synapses that transmit visual signals. The results revealed that retinal TH expression gradually decreased following optic nerve transection in rats housed under a normal day/night cycle reaching a minimum at 5 days. In contrast, retinal TH expression decreased to a minimum at 1 day following optic nerve transection in dark reared rats, gradually increasing afterward and reaching a normal level at 5 7 days. The number of TH-positive synaptic particles correlated with the TH levels indicating that dark rearing can help maintain TH expression during the synaptic degeneration stage （5 7 days after optic nerve injury） in retinal amacrine cells.

Tyrosine hydroxylase expression in the midbrain of Parkinson's disease model rats treated with Xifeng Dingchan decoction

This study showed that abnormal behavioral changes were greatly improved in rats displaying Parkinson＇s disease-like symptoms after intragastric administration of Xifeng Dingchan decoction at 15, 7.5, 3.75 g/kg per day. In addition, tyrosine hydroxylase mRNA expression in the substantia nigra of the midbrain was up-regulated, and tyrosine hydroxylase content in the midbrain ventral tegmentum and substantia nigra pars compacta was also increased. The effect of administration of Xifeng Dingchan decoction at 7.5 g/kg per day was similar to that of Madopar at 67.5 mg/kg per day. These results indicate that the therapeutic effect of Xifeng Dingchan decoction on Parkinson＇s disease is associated with the up-regulated protein and mRNA expression of tyrosine hydroxylase in the midbrain.

Tyrosine Hydroxylase as a Target for Deltamethrin in the Nigrostriatal Dopaminergic Pathway

Objective To study the effects of deltamethrin on tyrosine hydroxylase in nigrostriatum of male rats. Methods Sprague-Dawley rats were daily treated with deltamethrin at 6.25 or 12.5 mg/kg body weight by gavage for 10 days. Then HPLC-fluorescence detection was used to analyze the contents of dopamine （DA）, 3,4-dihydmxyphenylacetic acid （DOPAC） and homoranillic acid （HVA） in substantial nigra and striatum. The activities of tyrosine hydroxylase （TH） were also detected by HPLC-fluorescence detection. TH mRNA or TH protein levels were measured by RT-PCR and immunohistochemistry method. Results The content of DA in stfiatum was significantly decreased by the treatments, suggesting an inhibition of DA synthesis by deltamethrin. The contents of DA metabolites DOPAC and HVA increased, indicating increased dopamine turnover. Furthermore, deltamethrin significantly decreased the activity, as well as the mRNA and protein levels of TH. Conclusions These findings reveal a novel aspect of deltamethfin neurotoxicity and suggest tyrosine hydroxylase as a molecular target of deltamethin on dopamine metabolism in the nigrostriatal pathway.

Treatment time influences the effects of a low-frequency pulsed electric field on synthesis of tyrosine hydroxylase and dopamine in PC12 cells

BACKGROUND： Electromagnetic radiation can influence dopamine （DA） synthesis in brain tissues or ceils, but electromagnetic frequencies, intensities, and radiation time can produce different effects. In addition, the signal pathway by which electromagnetic radiation influences DA synthesis remains controversial. OBJECTIVE： To determine tyrosine hydroxylase （TH） expression in PC12 cells and DA levels in cell culture media after different periods of low-frequency pulsed electric field （LF-PEF） stimulation, and to determine how LF-PEF signaling stimulates TH synthesis using inhibitors. DESIGN, TIME AND SETTING： A parallel, controlled, cell experiment was performed at the Laboratory of Cell Biology, School of Life Science, East China Normal University, between January and October 2006. MATERIALS： PC12 cells were purchased from the Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, China. Nerve growth factor was purchased from PeproTech, USA. The protein kinase A inhibitor, H-89, and mitogen-activated protein kinase kinase inhibitor, U0126, were purchased from Sigma, USA. METHODS： （1） Following routine culture in Dulbecco＇s modified eagle medium, primary PC12 cells were stimulated under LF-PEF （pulse frequency 50.Hz, pulse width 20 μs, peak field strength 1 V/m） for 5, 10, 15, 20, and 30 minutes. （2） Inhibitors （H-89 or U0126, 1 μmol/L） were added 30 minutes before LF-PEF stimulation for 10 minutes. MAIN OUTCOME MEASURES： （1） TH expression was determined by Western blot in PC12 cells at 0.5, 1,2, 3, and 4 days after LF-PEF stimulation. Similarly, DA was measured by high-performance liquid chromatography in media at 2, 3, 4, or 5 days after LF-PEE （2） TH expression was detected 1 day after H-89 or U0126 treatment and LF-PEE RESULTS： （1） Short-term LF-PEF stimulation （5 and 10 minutes） increased TH expression and media DA levels after short-term culture （2 days） （P 〈 0.01）, but both parameters decreased with longer culture （3 4 days） （P 〈 0.01）. Long-term LF-PEF stimulation （15, 20, or 30 minutes） decreased TH and DA synthesis, followed by a rapid increase （P 〈 0.01）. （2） H89 could completely inhibit TH expression in PC12 cells stimulated by LF-PEF for 10 minutes, while the inhibition rate of U0126 was 53.2%. CONCLUSION： Short-term LF-PEF first promotes then inhibits, while long-term LF-PEF first inhibits then promotes, TH and DA synthesis. LF-PEF stimulation regulates TH expression primarily by activating protein kinase A to regulate DA synthesis.

Tyrosine hydroxylase gene transfections to different sites of striatum in the rat model of Parkinson’s disease

The use of gene therapy has been intensively studied as a potential method to treat Parkinson’s disease (PD) and other degenerative brain diseases. However, the effects of experimental measures and approaches on the outcome of gene delivery or on the physiological state of target tissues have not been analyzed as much and systematically. Therefore, we have infused adenovirus vectors expressing either a therapeutic tyrosine hydroxylase (TH) gene or a lacZ reporter gene into striatum in a rat model of PD. The experimental procedures were tested using the Ad lacZ vector in order to optimize concentrations, volumes, infusion speeds and transfection times. The expression of Ad lacZ vector was lower and declined earlier in the lesioned than unlesioned striatum suggesting that the lesion affects on the transfection efficiency and outcome of gene transfection. The effect of three different approaches of Ad TH vector transfection was compared: 1) the delivery of Ad TH gene vector alone into one single site of striatum, 2) the delivery of Ad TH gene vector alone into multiple sites of striatum, and 3) the delivery of Ad TH gene vector into one site of striatum followed by a continuous infusion of tetrahydrobiopterin (BH4) cofactor with a mini pump. There was a small and transient unsignificant decrease in the turning behavior when the Ad TH vector was delivered into one site of the striatum. Simultaneous infusion into several sites or together with BH4 cofactor did not improve more the effect of gene delivery. Thus, although the effects were unsignificant, the Ad TH transfection seemed to decrease the turning behavior in the rat model of PD and the optimal effect was seen at some specific doses and time points. Furthermore, the outcome of gene therapy could depend in addition to the amount and efficacy of gene vectors also on the physiological state and experimental strategies.

A core-satellite-like nanoassembly reverses a decisive tyrosine hydroxylase loss in degenerative dopaminergic neurons

In recent years,neurodegenerative diseases,such as Parkinson’s or Alzheimer’s diseases,are rapidly rising in prevalence.The main hallmark of Parkinson’s disease is the falling levels of neurotransmitter dopamine in the mid-brain with dopaminergic neurons losing.Typical therapeutic solutions,including drugs,deep brain stimulation,and cell transplantation,can only alleviate the symptoms of Parkinson’s disease.It is a tremendous challenge to reverse the function degeneration of the crucial dopaminergic neurons.Herein,we develop a core-satellite-like nanoassembly(PDA-AFn(by integrating polydopamine nanoparticles and apoferritin))to raise the expression of tyrosine hydroxylase(TH),a rate-limiting enzyme in the formation of the dopamine.Both components in the nanoassembly could cooperate with each other,not only elaborately regulate the iron homeostasis and redox microenvironment,but also utilize excessive reactive oxygen species(ROS)and iron ions in the damaged neurons to supply extra dopamine and enhance TH activity,and consequently restore the function of the degenerated neurons.Remarkably,the nanoassembly-treatment relieves the dyskinesia and dramatical increases the tyrosine hydroxylase and dopamine level in the midbrain of Parkinson’s disease model mice.It is an explicit yet inspiring advance in treatment of the neurodegeneration.

Effect of Bushen Huoxue Decoction(补肾活血饮) on the Orphan Receptor and Tyrosine Hydroxylase in the Brain of Rats with Parkinson's Disease

Objective：To explore the effect of Bushen Huoxue Decoction（补肾活血饮,BHD） on the orphan receptor（Nurr1） and tyrosine hydroxylase（TH） in the brain of rats with Parkinson＇s disease（PD）.Methods：One hundred and twenty SD rats were divided into 100 in the model group and 20 in the normal control group,fifty-eight SD rats from the model group,established into PD model successfully by injuring their substantia nigra （SSN） with 6-hydroxydopamine,were divided equally into the model group and the test group,and they were treated with saline and BHD,respectively,for eight successive weeks.The change in the rats＇ behavior before and after treatment was observed by counting the cycles of rotation induced by apomorphine injection; the pathology of neurons,level of Nurr1 mRNA expression,and amount of TH positive cells in SSN were observed after treatment.Results：The rats＇ behavior was improved in the tested group significantly,the rotation cycle after treatment being 84.0±20.0 cycles/40 min,which was significantly lower than that in the model group（377.0±62.3 cycles/40 min,P〈0.01）.Besides,the Nurr1 mRNA expression and TH positive cell in the test group were 0.97±0.15 and 49.40±14.72,respectively,which were significantly higher than those in the model group,0.22±0.03 and 5.45±2.58,respectively（all P〈0.01）.Conclusion：BHD could treat PD by enhancing the Nurr1 mRNA expression,increasing the TH content in brain,and promoting the repairing of injured neuron in cerebral SSN.

CHCHD2 Thr61Ile mutation impairs F1F0-ATPase assembly in in vitro and in vivo models of Parkinson's disease

Mitochondrial dysfunction is a significant pathological alte ration that occurs in Parkinson's disease(PD),and the Thr61lle(T61I)mutation in coiled-coil helix coiled-coil helix domain containing 2(CHCHD2),a crucial mitochondrial protein,has been reported to cause Parkinson's disease.FIFO-ATPase participates in the synthesis of cellular adenosine triphosphate(ATP)and plays a central role in mitochondrial energy metabolism.However,the specific roles of wild-type(WT)CHCHD2 and T611-mutant CHCHD2 in regulating F1FO-ATPase activity in Parkinson's disease,as well as whether CHCHD2 or CHCHD2 T61I affects mitochondrial function through regulating F1FO-ATPase activity,remain unclea r.Therefore,in this study,we expressed WT CHCHD2 and T61l-mutant CHCHD2 in an MPP^(+)-induced SH-SY5Y cell model of PD.We found that CHCHD2 protected mitochondria from developing MPP^(+)-induced dysfunction.Under normal conditions,ove rexpression of WT CHCHD2 promoted F1FO-ATPase assembly,while T61I-mutant CHCHD2 appeared to have lost the ability to regulate F1FO-ATPase assembly.In addition,mass spectrometry and immunoprecipitation showed that there was an interaction between CHCHD2 and F1FO-ATPase.Three weeks after transfection with AAV-CHCHD2 T61I,we intraperitoneally injected 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine into mice to establish an animal model of chronic Parkinson's disease and found that exogenous expression of the mutant protein worsened the behavioral deficits and dopaminergic neurodegeneration seen in this model.These findings suggest that WT CHCHD2 can alleviate mitochondrial dysfunction in PD by maintaining F1F0-ATPase structure and function.

Rapamycin reverses ferroptosis by increasing autophagy in MPTP/MPP+-induced models of Parkinson's disease

Parkinson’s disease is a neurodegenerative disorder,and fe rroptosis plays a significant role in the pathological mechanism underlying Parkinson’s disease.Rapamycin,an autophagy inducer,has been shown to have neuroprotective effects in Parkinson’s disease.However,the link between rapamycin and ferroptosis in Parkinson’s disease is not entirely clear.In this study,rapamycin was administe red to a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced Parkinson’s disease mouse model and a 1-methyl-4-phenylpyridinium-induced Parkinson’s disease PC12 cell model.The results showed that rapamycin improved the behavioral symptoms of Parkinson’s disease model mice,reduced the loss of dopamine neurons in the substantia nigra pars compacta,and reduced the expression of ferroptosis-related indicators(glutathione peroxidase 4,recombinant solute carrier family 7,member 11,glutathione,malondialdehyde,and reactive oxygen species).In the Parkinson’s disease cell model,rapamycin improved cell viability and reduced ferro ptosis.The neuroprotective effect of rapamycin was attenuated by a ferroptosis inducer(methyl(1S,3R)-2-(2-chloroacetyl)-1-(4-methoxycarbonylphenyl)-1,3,4,9-tetrahyyridoindole-3-carboxylate)and an autophagy inhibitor(3-methyladenine).Inhibiting ferro ptosis by activating autophagy may be an important mechanism by which rapamycin exerts its neuroprotective effects.Therefo re,the regulation of ferroptosis and autophagy may provide a therapeutic target for drug treatments in Parkinson’s disease.

Single-nuclei RNA sequencing uncovers heterogenous transcriptional signatures in Parkinson's disease associated with nuclear receptor-related factor 1 defect

Previous studies have found that deficiency in nuclear receptor-related factor 1(Nurr1),which participates in the development,differentiation,survival,and degeneration of dopaminergic neurons,is associated with Parkinson s disease,but the mechanism of action is perplexing.Here,we first asce rtained the repercussion of knocking down Nurr1 by pe rforming liquid chromatography coupled with tandem mass spectrometry.We found that 231 genes were highly expressed in dopaminergic neurons with Nurr1 deficiency,14 of which were linked to the Parkinson’s disease pathway based on Kyoto Encyclopedia of Genes and Genomes analysis.To better understand how Nurr1 deficiency autonomously invokes the decline of dopaminergic neurons and elicits Parkinson’s disease symptoms,we performed single-nuclei RNA sequencing in a Nurr1 LV-shRNA mouse model.The results revealed cellular heterogeneity in the substantia nigra and a number of activated genes,the preponderance of which encode components of the major histocompatibility Ⅱ complex.Cd74,H2-Ab1,H2-Aα,H2-Eb1,Lyz2,Mrc1,Slc6α3,Slc47α1,Ms4α4b,and Ptprc2 were the top 10 diffe rentially expressed genes.Immunofluorescence staining showed that,after Nurr1knockdown,the number of CD74-immunoreactive cells in mouse brain tissue was markedly increased.In addition,Cd74 expression was increased in a mouse model of Parkinson’s disease induced by treatment with 6-hydroxydopamine.Ta ken togethe r,our res ults suggest that Nurr1 deficiency results in an increase in Cd74 expression,thereby leading to the destruction of dopaminergic neuro ns.These findings provide a potential therapeutic target for the treatment of Parkinson’s disease.

Treadmill step training promotes spinal cord neural plasticity after incomplete spinal cord injury

A large body of evidence shows that spinal circuits are significantly affected by training, and that intrinsic circuits that drive locomotor tasks are located in lumbosacral spinal segments in rats with complete spinal cord transection. However, after incomplete lesions, the effect of treadmil training has been debated, which is likely because of the difficulty of separating spontaneous stepping from specific training-induced effects. In this study, rats with moderate spinal cord contusion were sub-jected to either step training on a treadmil or used in the model （control） group. The treadmil training began at day 7 post-injury and lasted 20 ± 10 minutes per day, 5 days per week for 10 weeks. The speed of the treadmil was set to 3 m/min and was increased on a daily basis according to the tolerance of each rat. After 3 weeks of step training, the step training group exhibited a sig-nificantly greater improvement in the Basso, Beattie and Bresnahan score than the model group. The expression of growth-associated protein-43 in the spinal cord lesion site and the number of tyrosine hydroxylase-positive ventral neurons in the second lumbar spinal segment were greater in the step training group than in the model group at 11 weeks post-injury, while the levels of brain-derived neurotrophic factor protein in the spinal cord lesion site showed no difference between the two groups. These results suggest that treadmil training significantly improves functional re-covery and neural plasticity after incomplete spinal cord injury.

Laterodorsal Tegmentum and Pedunculopontine Tegmental Nucleus Circuits Regulate Renal Functions: Neuroanatomical Evidence in Mice Models

Neurons in the laterodorsal tegmentum (LDTg) and pedunculopontine tegmental nucleus (PPTg) play important roles in central autonomic circuits of the kidney. In this study, we used a combination of retrograde tracers pseudorabies virus (PRV)-614 and fluorescence immunohistochemistry to characterize the neuroanatomic substrate of PPTg and LDTg innervating the kidney in the mouse. PRV-614-infected neurons were retrogradely labeled in the rostral and middle parts of LDTg, and the middle and caudal parts of PPTg after tracer injection in the kidney. PRV-614/TPH double-labeled neurons were mainly localized in the rostral of LDTg, whereas PRV-614/TH neurons were scattered within the three parts of LDTg. PRV-614/TPH and PRV-614/TH neurons were located predominantly in the caudal of PPTg (cPPTg). These data provided direct neuroanatomical foundation for the identification of serotonergic and catecholaminergic projections from the mid-brain tegmentum to the kidney.

Bone marrow-derived mesenchymal stem cells increase dopamine synthesis in the injured striatum

Previous studies showed that tyrosine hydroxylase or neurturin gene-modified cells transplanted into rats with Parkinson＇s disease significantly improved behavior and increased striatal dopamine content. In the present study, we transplanted tyrosine hydroxylase and neurturin gene-modified bone marrow-derived mesenchymal stem cells into the damaged striatum of Parkinson＇s disease model rats. Several weeks after cell transplantation, in addition to an improvement of motor function tyrosine hydroxylase and neurturin proteins were up-regulated in the injured striatum, and importantly, levels of dopamine and its metabolite 3,4-dihydroxyphenylacetic acid increased significantly. Furthermore, the density of the D2 dopamine receptor in the postsynaptic membranes of dopaminergic neurons was decreased. These results indicate that transplantation of tyrosine hydroxylase and neurturin gene-modified bone marrow-derived mesenchymal stem cells increases dopamine synthesis and significantly improves the behavior of rats with Parkinson＇s disease.

Downregulation of thioredoxin reductase 1 expression in the substantia nigra pars compacta of Parkinson's disease mice

Because neurons are susceptible to oxidative damage and thioredoxin reductase 1 is extensively distributed in the central nervous system and has antioxidant properties, we speculated that the enzyme may be involved in the pathogenesis of Parkinson＇s disease. A Parkinson＇s disease model was produced by intraperitoneal injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine into C57BL/6 mice. Real-time reverse transcription-PCR, western blot analysis and colorimetric assay showed that the levels of thioredoxin reductase 1 mRNA and protein were decreased, along with a significant reduction in thioredoxin reductase activity, in the midbrain of Parkinson＇s disease mice compared with normal mice. Immunohistochemical staining revealed that the number of thioredoxin reductase 1-positive neurons in the substantia nigra pars compacta of Parkinson＇s disease mice was significantly decreased compared with normal mice. These experimental findings suggest that the expression of thioredoxin reductase 1 in the substantia nigra pars compacta of Parkinson＇s disease mice is significantly decreased, and that the enzyme may be associated with disease onset.

Role of calbindin-D28K in estrogen treatment for Parkinson’s disease

Studies have shown that estrogen has neuroprotective effects on the nigrostriatal system. The present study established a Parkinson＇s disease model in C57BL/6 mice by intraperitoneal injection of 1-methyl-4-phenyl-1,2,3,6-tetrapyridine. The mice were subjected to 1713 estradiol injection into the lateral ventricle. Immunofluorescence double staining showed that estrogen increased tyrosine hydroxylase and calbindin-D28K expression and co-expression in dopaminergic neurons of midbrain substantia nigra pars compacta of model mice. Behavior experiments showed that estrogen improved swimming and hanging behaviors in this mouse model of Parkinson＇s disease.

Zhichan powder regulates nigrostriatal dopamine synthesis and metabolism in Parkinson's disease rats

In this study, rat models of Parkinson＇s disease induced by substantia nigra injection of 6-hydroxy-dopamine were intragastrically administered Zhichan powder daily for 50 days. Reverse transcription PCR results showed that tyrosine hydroxylase mRNA expression in the rat substantia nigra was significantly increased, while monoamine oxidase B mRNA expression was significantly decreased in the Zhichan powder group, compared with the model group. In addition, the levels of striatal dopamine and homovanillic acid, the ratio of dopamine to homovanillic acid, and the activity of blood superoxide dismutase were all higher in the Zhichan powder group than in the model group but the content of malondialdehyde in blood was lower. Our experimental findings indicate that Zhichan powder has an antioxidant effect, it can regulate the expression of monoamine oxidase B and tyrosine hydroxylase in the substantia nigra of Parkinson＇s disease rats, and it can facilitate the secretion of striatal dopamine and its metabolite homovanillic acid.

Degree of dopaminergic degeneration measured by ^(99m)Tc-TRODAT-1 SPECT/CT imaging

To prevent and treat Parkinson＇s disease in its early stages,it is essential to be able to detect the degree of early dopaminergic neuron degeneration.Dopamine transporters（DAT） in the striatum regulate synaptic dopamine levels,and striatal ^99mTc-TRODAT-1 single-photon emission computed tomography（-SPECT） imaging is a marker for presynaptic neuronal degeneration.However,the association between the degree of dopaminergic degeneration and in vivo ^99mTc-TRODAT-1 SPECT imaging is unknown.Therefore,this study investigated the association between the degree of 6-hydroxydopamine（6-OHDA）-induced dopaminergic degeneration and DAT imaging using^99mTc-TRODAT-1 SPECT in rats.Different degrees of nigrostriatal dopamine depletion were generated by injecting different doses of 6-OHDA（2,4,and 8 μg） into the right medial forebrain bundle.The degree of nigrostriatal dopaminergic neuron degeneration was assessed by rotational behavior and immunohistochemical staining.The results showed that striatal ^99mTc-TRODAT-1 binding was significantly diminished both in the ipsilateral and the contralateral sides in the 4 and 8 μg 6-OHDA groups,and that DAT ^99mTc-TRODAT-1 binding in the ipsilateral striatum showed a high correlation to apomorphine-induced rotations at 8 weeks post-lesion（r = –0.887,P 〈 0.01）.There were significant correlations between DAT ^99mTc-TRODAT-1 binding in the ipsilateral striatum and the amount of tyrosine hydroxylase immunoreactive neurons in the ipsilateral substantia nigra in the 2,4,and 8 μg 6-OHDA groups at 8 weeks post-lesion（r = 0.899,P 〈 0.01）.These findings indicate that striatal DAT imaging using ^99mTc-TRODAT-1 is a useful technique for evaluating the severity of dopaminergic degeneration.

Features of adult neurogenesis and neurochemical signaling in the Cherry salmon Oncorhynchus masou brain

We investigated the distribution of gamma aminobutyric acid, tyrosine hydroxylase and nitric oxide-producing elements in a cherry salmon Oncorhynchus masou brain at various stages of postnatal ontogenesis by immunohistochemical staining and histochemical staining. The periventricular region cells exhibited the morphology of neurons and glia including radial glia-like cells and contained several neurochemical substances. Heterogeneous populations of tyrosine hydroxylase-, gamma aminobutyric acid-immunoreactive, as well as nicotinamide adenine dinucleotide phosphate diaphorase-positive cells were observed in proliferating cell nuclear antigen-immunoreactive proliferative zones in periventricular area of diencephalon, central grey layer of dorsomedial tegmentum, medulla and spinal cord. Immunolocalization of Pax6 in the cherry salmon brain revealed a neuromeric construction of the brain at various stages of postnatal ontogenesis, and this was confirmed by tyrosine hydroxylase and gamma aminobutyric acid labeling.

Degenerative alterations in noradrenergic neurons of the locus coeruleus in Alzheimer's disease

Mice carrying mutant amyloid precursor protein and presenilin-1 genes （APP/PS1 double trans- genic mice） have frequently been used in studies of Alzheimer＇s disease; however, such studies have focused mainly on hippocampal and cortical changes. The severity of Alzheimer＇s disease is known to correlate with the amount of amyloid-13 protein deposition and the number of dead neurons in the locus coeruleus. In the present study, we assigned APP/PS1 double transgenic mice to two groups according to age： young mice （5-6 months old） and aged mice （16-17 months old）. Age-matched wild-type mice were used as controls. Immunohistochemistry for tyrosine hydroxylase （a marker of catecholaminergic neurons in the locus coeruleus） revealed that APP/PS1 mice had 23% fewer cells in the locus coeruleus compared with aged wild-type mice. APP/PS1 mice also had increased numbers of cell bodies of neurons positive for tyrosine hydroxylase, but fewer tyrosine hydroxylase-positive fibers, which were also short, thick and broken. Quantitative analysis using unbiased stereology showed a significant age-related increase in the mean volume of tyrosine hy- droxylase-positive neurons in aged APP/PS1 mice compared with young APP/PS1 mice. Moreover, the mean volume of tyrosine hydroxylase-positive neurons was positively correlated with the total volume of the locus coeruleus. These findings indicate that noradrenergic neurons and fibers in the locus coeruleus are predisposed to degenerative alterations in APP/PS1 double transgenic mice.