Effect of muscarinic agonists on the release of 3H-norepinephrine and 3H-dopamine by potassium and electrical stimulation from rat brain slices

The effect of acetylcholine (ACh) on the release of ³H-norepinephrine (NE) from the cerebellum and ³H-dopamine (DA) from the striatum following the administration of potassium chloride or electrical field stimulation was studied in superfused brain slices. ACh in conc. of 10^?6 and 10^?5M significantly inhibited the release of ³H-NE from cerebellar slices and ³H-DA from striatal slices following 2 min infusion of 50mM potassium chloride. In addition ACh produced a dose-dependent inhibition of the release of ³H-DA from striatal slices following electrical stimulation. The results obtained in the present study are quite consistent with the concept that a muscarinic inhibitory mechanism may be operative on noradrenergic and dopaminergic neurons in the brain.     

Synthetic analgesics and other phenylpiperidines: effects on uptake and storage of dopamine and other monoamines mouse forebrain tissue

The neurotoxin N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) can induce degeneration of dopamine (DA) and other central monoamine neurons, leading to Parkinson's disease-like effects in man, monkey, and mouse. MPTP and other substituted phenylpiperidines related to synthetic analgesics including alphaprodine and meperidine were evaluated for potency vs. uptake of 0.1 microM tritiated DA, norepinephrine (NE), or serotonin (5HT) in synaptosomal preparations of mouse striatum or cerebral cortex. The most potent inhibitor of the uptake of 3H-DA was N-methyl-4-phenylpyridinium ion (MPP+; IC50 = 1 microM, Ki = 0.4 microM), a metabolite of MPTP; its effect was competitive and reversible. Other analogs of MPTP: the N-ethylindole AHR-1709, N,N-dimethyl-MPTP, and N-methyl-4-phenylpiperidine were all more potent than MPTP against 3H-DA uptake. N-dealkylation and N-propyl substitution, as well as pyridine ring substitution, decreased affinity for DA uptake while 3',4'-dihydroxyphenyl substitution increased potency and selectivity for catecholamine uptake, and quarternarization of the pyridine ring also increased potency against DA uptake. Active compounds showed higher potency against the uptake of NE than of DA. MPP+ was also more potent than MPTP in releasing endogenous DA from striatal synaptosomes (EC50 = 3 vs. 30 microM), but did not release the cytoplasmic markers tyrosine hydroxylase and lactate dehydrogenase (LDH). In contrast to MPTP, synthetic phenylpiperidine analgesics, their potential metabolites and the experimental neuroleptic agent AHR-1709 all failed to deplete striatal DA in vivo, even if active in vitro against DA uptake.     

腺苷受体拮抗剂对帕金森病小鼠神经递质的影响

运用神经毒剂ＭＰＴＰ（１－ｍｅｔｈｙ－４－ｐｈｅｎｙ－１,２,３,６－ｔｅｔｒａｈｙｄｒｏｐｙｒｉｄｉｎｅ）制作的ＩＣＲ小鼠帕金森病模型,通过荧光测定方法和免疫组织化学方法,测定ＭＰＴＰ及腺甘Ａ２ａ受体拮抗剂喹唑啉（Ｑｕｉｎａｚｏｌｉｎｅ,ＣＰ６６７１３）对单胺类神经递质去甲肾上腺素（ＮＡ）、多巴胺（ＤＡ）、５－羟色胺（５－ＨＴ）及其代谢产物５－羟吲哚乙酸（５－ＨＩＡＡ）和氨基酸类神经递质γ－氨基     

Studies on the mechanisms of L-dopa-induced depletion of 5-hydroxytryptamine in the mouse brain

The administration of L-dopa to mice causes an increase in the brain concentrations of dopa and dopamine which is related temporally to a reduction in the brain concentration of 5HT. These effects occur concurrently with a reduction in the conversion of intravenously administered ³H-tryptophan to ³H-5HT without an alteration in the accumulation of ³H-tryptophan in the brain. The L-dopa-induced changes in the brain concentrations of dopa, dopamine and 5HT are not altered by pretreatment with drugs (imipramine, chlorimipramine, benztropine, cocaine) which inhibit the neuronal uptake of amines. Current evidence suggests that L-dopa is decarboxylated in 5HT neurons to dopamine, which displaces 5HT from intraneuronal storage sites.     

Selective inhibition of serotonin uptake by trazodone,a new antidepressant agent

The inhibitory effect of trazodone, a non tricyclic antidepressant, on 5-HT and catecholamine uptake into the synaptosomal preparation from the rat brain was compared with that of chlorimipramine. The inhibition of 5-HT uptake by trazodone is competitive with a K_i of 1.6 × 10^?6 M. Trazodone inhibits ³H-5-HT, ³H-NE and ³H-DA uptake with an IC₅₀ of 1.4 × 10^?6, 3.1 × 10^?4 and 5.2 × 10^?4 M, respectively. Therefore trazodone is 220 and 370 times more potent in inhibiting 5-HT than NE and DA uptake, respectively. The respective IC₅₀ values of chlorimipramine were 0.9 × 10^?7, 3.6 × 10^?6 and 4.0 × 10^?6 M for ³H-5-HT, ³H-NE and ³H-DA.     

THE EFFECT OF AMINO-OXYACETIC ACID ON BRAIN CATECHOLAMINES

Abstract— —Administration of amino-oxyacetic acid (AOAA) to rats induced a pronounced decrease of midbrain norepinephrine (NE) and adrenal epinephrine (E) after 30 min, at which time the GABA level of midbrain had increased to 117 per cent of the initial value. The concentrations of NE in the pons-medulla and of dopamine (DA) in the cerebral hemispheres were not changed.
Further increases in brain GABA were accompanied by a rise of NE in midbrain and pons-medulla beginning 1 hr after AOAA administration. A rise of cerebral DA level was observed only after 4 hr. Six hours after AOAA administration the levels of both NE and DA in brain were reduced.
From the results of these and other studies, where administration of small amounts of GABA were shown to affect brain NE and serotonin levels, it is suggested that monoamines may be involved in the physiological action of GABA in the brain.     

Prevention of the Nigrostriatal Toxicity of 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine by Inhibitors of 3,4-Dihydroxyphenylethylamine Transport

The 3,4-dihydroxyphenylethylamine (DA, dopamine) uptake inhibitors GBR 13,069, amfonelic acid, WIN-35,065-2, WIN-35,428, nomifensine, mazindol, cocaine, McN-5908, McN-5847, and McN-5292 were effective in preventing [3H]DA and [3H]1-methyl-4-phenylpyridinium (MPP+) uptake in rat and mouse neostriatal tissue slices. These DA uptake inhibitors also were effective in attenuating the MPP+-induced release of [3H]DA in vitro. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration to mice (6 X 25 mg/kg i.p.) resulted in a large (70-80%) decrement in neostriatal DA. WIN-35,428 (5 mg/kg), GBR 13,069 (10 mg/kg), McN-5292 (5 mg/kg), McN-5908 (2 mg/kg), and amfonelic acid (2 mg/kg), when administered intraperitoneally 30 min prior to each MPTP injection, fully protected against MPTP-induced neostriatal damage. Other DA uptake inhibitors showed partial protection in vivo at the doses selected. Desmethylimipramine did not prevent [3H]MPP+ uptake or MPP+-induced release of [3H]DA in vitro, and did not protect against MPTP neurotoxicity in vivo. These results support the hypothesis put forth previously by others that the active uptake of MPP+ by dopaminergic neurons is necessary for toxicity.     

Effects of 1-Methyl-4-Phenyl-1,2,5,6-Tetrahydropyridine and Related Compounds on the Uptake of [3H]3,4-Dihydroxyphenylethylamine and [3H]5-Hydroxytryptamine in Neostriatal Synaptosomal Preparations

1-Methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP) is known to cause a destruction of the dopaminergic nigrostriatal pathway in certain animal species including mice. MPTP and some structurally related analogs were tested in vitro for their capacity to inhibit the uptake of [3H]3,4-dihydroxyphenylethylamine-([3H]DA), [3H]5-hydroxytryptamine ([3H]5-HT), and [3H]gamma-aminobutyric acid [( 3H]GABA) in mouse neostriatal synaptosomal preparations. MPTP was a very potent inhibitor of [3H]5-HT uptake (IC50 value 0.14 microM), a moderate inhibitor of [3H]DA uptake (IC50 value 2.6 microM), and a very weak inhibitor of [3H]GABA uptake (no significant inhibition observed at 10 microM MPTP). In other experiments, MPTP caused some release of previously accumulated [3H]DA and [3H]5-HT, but in each case MPTP was considerably better as an uptake inhibitor than as a releasing agent. The 4-electron oxidation product of MPTP, i.e., 1-methyl-4-phenyl-pyridinium iodide (MPP+), was a very potent inhibitor of [3H]DA uptake (IC50 value 0.45 microM) and of [3H]5-HT uptake (IC50 value 0.78 microM) but MPP+ was a very weak inhibitor of [3H]GABA uptake. These data may have relevance to the neurotoxic actions of MPTP.     

1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine Metabolism and l-Methyl-4-Phenylpyridinium Uptake in Dissociated Cell Cultures from the Embryonic Mesencephalon

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a contaminant found in a synthetic illicit drug, can elicit in humans and monkeys a severe extrapyramidal syndrome similar to Parkinson's disease. It also induces alterations of the dopamine (DA) pathways in rodents. MPTP neurotoxicity requires its enzymatic transformation into 1-methyl-4-phenylpyridinium (MPP+) by monoamine oxidase followed by its concentration into target cells, the DA neurons. Here, we show that mesencephalic glial cells from the mouse embryo can take up MPTP in vitro, transform it into MPP+, and release it into the culture medium. MPTP is not taken up by neurons from either the mesencephalon or the striatum in vitro (8 days in serum-free conditions). However, mesencephalic neurons in culture revealed a high-affinity uptake mechanism for the metabolite MPP+, similar to that for DA. The affinity (Km) for DA uptake is fivefold higher than that for MPP+ (0.2 and 1.1 microM, respectively), whereas the number of uptake sites for MPP+ is double (Vmax = 25 and 55 pmol/mg of protein/min for DA and MPP+, respectively). Mazindol, a DA uptake inhibitor, blocks the uptake of DA and MPP+ equally well under these conditions. Moreover, by competition experiments, the two molecules appear to use the same carrier(s) to enter DA neurons. Small concentrations of MPP+ are also taken up by striatal neurons in vitro. The amount taken up represented less than 10% of the MPP+ uptake in mesencephalic neurons. Depolarization induced by veratridine released comparable proportions of labeled DA and MPP+ from mesencephalic cultures.(ABSTRACT TRUNCATED AT 250 WORDS)     

<Emphasis Type="Italic">Cynomorium songaricum</Emphasis> Extracts Functionally Modulate Transporters of γ-Aminobutyric Acid and Monoamine

Cynomorium songaricum Rupr. (SY) is a central nervous system-oriented herb material that has actions of anti-dementia, anti-epilepsy, and anti-stress. It is unclear whether SY would be biologically active in functionally regulating neurotransmitter transporters. Here, we assessed these potential actions using Chinese hamster ovary cells expressing γ-aminobutyric acid (GABA) transporter (GAT-1), dopamine transporter (DAT), norepinephrine transporter (NET), or serotonin transporter (SERT) (i.e. G1, D8, N1, or S6 cells, respectively). It was shown that SY extracts, such as SYw, SYa, SYp, SYc, SYe, and SYb (SY water, ethanol, petroleum ether, chloroform, ethyl acetate, and n-butyl alcohol extract, respectively) increased dopamine/norepinephrine (DA/NE) uptake by corresponding D8/N1 cells and decreased γ-aminobutyric acid/serotoin (GABA/5HT) uptake by corresponding G1/S6 cells; wherein, the potency or efficacy of SYc for up-regulating DA/NE uptake and that of SYb for inhibiting GABA/5HT uptake were relatively stronger. Additionally, GABA/5HT-uptake inhibition by SY extracts were also seen in cortical synaptosomes, and DA/NE-uptake enhancement by SYc was dependent on the activity of DAT and NET. Thus, SY extracts especially SYc and SYb are novel neurotransmitter-transporter modulators functioning as DAT/NET activators and/or GAT-1/SERT inhibitors.     

Uptake of biogenic amines by glial cells in culture I. A neuronal-like transport system for serotonin

Rat C6 astrocytoma cells take up serotonin (5HT) via a high affinity carrier mediated system with Km of 1 micromolar, and a second component of lower affinity. This high affinity 5HT transport system is rapid, concentrative, and highly sodium and temperature dependent. Chlorimipramine and Lilly 110140 preferentially block the glial 5HT but not NE uptake. This preferential inhibition has previously been shown for synaptosomes and brain slices. Norepinerphrine (NE) and to a lesser extent dopamine (DA) block the glial 5HT uptake, suggesting a partial overlap between the catecholamine and indoleamine glial carrier systems. 5-Hydroxy but not 6-hydroxy dopamine inhibits the high affinity 5HT transport in glia. A variety of ring hydroxylated indoleamine analogs block this glial 5HT transport; of the compounds tested, 5, 7 dihydroxytryptamine is the least effective inhibitor. Phenylethylamine (PEA) and its 0-methylated derivatives block synaptosomal and glial 5HT transport equally well. These observations suggest that cultured C6 cells used as models of glia possess a 5HT transport system which kinetically and pharmacologically resembles a neuronal 5HT transport system.     

Protection and Potentiation of 1-Methyl-4-Phenylpyridinium-Induced Toxicity by Cytochrome P450 Inhibitors and Inducer May Be Due to the Altered Uptake of the Toxin

Abstract: Earlier studies from our laboratory have demonstrated that 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) toxicity could be modulated by inhibitors and inducer of cytochrome P450 (P450) in an in vitro model consisting of sagittal slices of mouse brain. To understand the molecular mechanisms underlying the role of P450 on MPTP toxicity, it was undertaken to study the effect of the modulators of P450 on the toxicity of the metabolite of MPTP, namely, 1-methyl-4-phenylpyridinium ion (MPP⁺). Incubation of mouse brain slices with various concentrations of MPP⁺ (1–100 µ M ) resulted in dose-dependent inhibition of mitochondrial enzyme NADH-dehydrogenase (NADH-DH) and leakage of the cytosolic enzyme lactate dehydrogenase from the slice into the medium. MPP⁺-induced toxicity was abolished by pretreatment of the slices with inhibitors of monoamine oxidase (MAO; pargyline and deprenyl) or inhibitors of P450 (piperonyl butoxide or SKF-525A) or dopamine uptake blocker (GBR-12909), as measured by the activity of NADH-DH in slices and leakage of lactate dehydrogenase from the slice into the medium. Slices prepared from mice pretreated with phenobarbital (an inducer of P450) potentiated the toxic effects of MPP⁺. Pretreatment of slices with MAO-inhibitor, P450 inhibitors, or dopamine uptake blocker attenuated the uptake of MPP⁺ into the slices. In contrast, MPP⁺ uptake was significantly increased in slices prepared from phenobarbital-pretreated mice. Thus, both MAO and P450 inhibitors abolish the toxicity of MPP⁺ in the sagittal slices of mouse brain by altering the uptake of the toxin into the slices.     

Nisoxetine prevents the 6-hydroxydopamine induced decrease in post-decapitation convulsions

Intraventricular injection of 6-hydroxydopamine (60HDA) to rats caused a marked reduction in post-decapitation convulsions (PDC), which was also observed in rats given 60HDA systemically at birth. The reduction in PDC and norepinephrine (NE) content in brain and spinal cord was completely prevented by pretreatment with the selective norepinephrine uptake inhibitor, nisoxetine, but not by fluoxetine, a specific serotonin uptake inhibitor. Presumably nisoxetine prevented the reduction in PDC and NE levels by blocking the entry of 60HDA into the neuron via the membrane uptake pump, and thus preventing subsequent NE depletion and neuron degeneration. These data imply that NE neurons are involved in the neurological mechanism of PDC, although this does not exclude a role for other neurotransmitters such as serotonin (5HT) and dopamine (DA).     

INJECTION OF 6-HYDROXYDOPAMINE AND HYDROGEN PEROXIDE INTO THE SUBSTANTIA NIGRA AND LATERAL VENTRICLE OF THE CAT: SPECIFIC AND NONSPECIFIC EFFECTS ON STRIATAL BIOGENIC AMINES1

Attempting to clarify the mechanism by which intracerabral injection of 6-hydroxydopamine (60HDA) reduces catecholamines in the caudate nucleus (CN), we have tested two hypotheses: (1) 60HDA specifically attacks catecholaminergic neurons; (2) 60HDA liberates hydrogen peroxide (H₂O₂) which destroys neurons indiscriminately. To this end, we have injected high or low doses of 60HDA or equimolar amounts of H₂O₂ stereotaxically into the substantia nigra (SN) or the lateral ventricle of cats and have placed electrocoagulative lesions in the SN. We determined the CN levels of dopamine (DA), norepinephrine (NE) and serotonin (5HT) 7-10 days later. Nigral injections of high doses (8 μ mol) of either agent or low doses (80 nmol) of 60HDA decreased both DA and NE and induced similar histologic damage in the SN with neuronal drop-out at the periphery of the lesions. Injection of 80 nmol of H₂O₂ into the SN did not decrease CN amine levels and did not produce histologic damage in the SN. Electrocoagulation of the SN decreased CN DA and NE, but the histologic lesions failed to show any peripheral neuronal drop-out. Ventricular injections of high doses (16 μmol) of 60HDA or H₂O₂ reduced not only DA and NE but also 5HT levels in the ipsilateral CN. Low intraventricular doses (0-16 μmol) of 60HDA decreased only DA and NE without affecting 5HT levels in the CN whereas 0.16 μmol of H₂O₂ had no effect on any of the CN amines. The catecholamine-depleting effects of low doses (80 nmol) of 60HDA were significantly potentiated by inhibiting brain monoamine oxidase by 90 percent or more at the time and site of injection of 60HDA. These results suggest that the extracellular liberation of H₂O₂ from 60HDA could explain some possibly nonspecific effects of high doses of 60HDA; at lower doses, however, 60HDA may act via selective uptake into catecholaminergic neurons with subsequent intracellular release of H₂O₂.     

LY227942, an inhibitor of serotonin and norepinephrine uptake: biochemical pharmacology of a potential antidepressant drug

LY227942, (+/-)-N-methyl-3-(1-naphthalenyloxy)-3-(2-thiophene)propanamine ethanedioate, is a new, competitive inhibitor of monoamine uptake in synaptosomal preparations of rat brain. LY227942 inhibits uptake of serotonin (5-hydroxytryptamine, 5HT) and norepinephrine (NE) in cortical synaptosomes and uptake of dopamine (DA) in striatal synaptosomes with inhibitor constants (Ki values) of 8.5, 45 and 300 nM, respectively. Upon administration in vivo, LY227942 lowers 5HT and NE uptake in hypothalamus homogenates to half their respective control activities (ED50) at 0.74 and 1.2 mg/kg s.c., 7 and 12 mg/kg i.p., and 12 and 22 mg/kg p.o., but LY227942 at doses up to 30 mg/kg p.o. does not change DA uptake in striatal homogenates. Lowering of 5HT and NE uptake is demonstrated after 15 min and 6 hr, but has dissipated by 16 hr after oral administration. According to radioligand binding determinations, LY227942 possesses only weak affinity for muscarinic receptors, histamine-1 receptors, adrenergic receptors, dopamine receptors and serotonin receptors. These findings suggest that LY227942 has the pharmacological profile of an antidepressant drug and is useful to study the pharmacological responses of concerted enhancement of serotonergic and noradrenergic neurotransmission.     

Modulation of GABA-augmented norepinephrine release in female rat brain slices by opioids and adenosine

GABA_A receptor activation augments electrically-stimulated release of norepinephrine (NE) from rat brain slices. Because this effect is not observed in synaptoneurosomes, GABA probably acts on inhibitory interneurons to disinhibit NE release. To determine whether opioids or adenosine influence GABA-augmented NE release, hypothalamic and cortical slices from female rats were superfused with GABA or vehicle in the presence and absence of 10 M morphine or 100 M adenosine. GABA augments [³H]NE release in the cortex and hypothalamus. Morphine alone has no effect on [³H]NE release, but attenuates GABA augmentation of [³H]NE release in both brain regions. Adenosine alone modestly inhibits [³H]NE release in the cortex, but not in the hypothalamus. Adenosine inhibits GABA-augmented [³H]NE release in both brain regions. The general protein kinase inhibitor H-7, augments [³H]NE release in both brain regions and may have additive effects with GABA in cortical slices. These results implicate opioid and adenosine interneurons and possibly protein kinases in regulating GABAergic influences on NE transmission.     

A new in vitro approach for investigating the MPTP effect on DA uptake

Previous studies have shown that dopamine (DA) uptake was decreased after preincubation of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or 1-methyl-4-phenylpyridinium (MPP(+)) in in vitro slice and synaptosome models. The present study, conducted with and without preincubation, attempted to determine whether inhibition results from a direct effect of neurotoxins on neuronal DA transporter or from an alteration of the transporter secondary to other toxic events. DA uptake was inhibited about 50% in the presence of MPTP+O(2) or MPP(+) (0.1, 1 and 5 mM) in rat striatal slices and synaptosomes. Such inhibition was obtained in synaptosomes preincubated for 150 min with MPP(+) and then washed. Inhibition of DA uptake was lower in slices preincubated with MPTP (5 mM)+O(2) and then washed (30%). Experiments in synaptosomes prepared from slices preincubated with MPTP or MPP(+) showed greater inhibition of DA uptake with MPTP. The results suggest that the inhibition of DA uptake in vitro by MPTP or MPP(+) results initially from a direct effect on the transporter during its penetration in nerve endings and subsequently from a transporter alteration related to toxic events. Thus, the preincubation of striatal slices followed by DA uptake measurement in synaptosomes would appear to be a good in vitro model for studying the dopaminergic toxicity of MPTP.     

Analysis of γ-Aminobutyric AcidA Receptor Subunits in the Mouse Cochlea by Means of the Polymerase Chain Reaction

Abstract: Unlike 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which produces consistent decreases in levels of striatal dopamine (DA) with considerably smaller and more variable effects on mouse brain levels of serotonin (5-HT) and norepinephrine (NE), a novel amine-substituted MPTP analogue, 1-methyl-4-(2'-aminophenyl)-1,2,3,6-tetrahydropyridine (2'-NH₂-MPTP), administered in a standard mouse dosing paradigm for MPTP (20 mg/kg X 4) did not affect striatal DA but led to marked reductions (60–70%) in levels of 5-HT, 5-hydroxyindoleacetic acid (5-HIAA), and NE measured in frontal cortex and hippocampus 1 week after treatment. Another 2'-substituted MPTP analogue, 1-methyl-4-(2'-methylphenyl)-1,2,3,6-tetrahydropyridine, affected cortical and hippocampal 5-HT, 5-HIAA, and NE only minimally, while markedly reducing the DA content in striatum (90%), thus indicating that the substituent (-NH₂ versus -CH₃) at the 2'position is important for the differential effects of these MPTP analogues. In a replication study with a 3-week end point, hippocampal and cortical 5-HT, 5-HIAA, and NE levels remained depressed with no indication of recovery. These results suggest that 2'-NH₂-MPTP may be a novel, regionally selective neurotoxin for serotonergic and norad-renergic nerve terminals.     

Tat-Fused Recombinant Human SAG Prevents Dopaminergic Neurodegeneration in a MPTP-Induced Parkinson’s Disease Model

Excessive reactive oxygen species (ROS) generated from abnormal cellular process lead to various human diseases such as inflammation, ischemia, and Parkinson’s disease (PD). Sensitive to apoptosis gene (SAG), a RING-FINGER protein, has anti-apoptotic activity and anti-oxidant activity. In this study, we investigate whether Tat-SAG, fused with a Tat domain, could protect SH-SY5Y neuroblastoma cells against 1-methyl-4-phenylpyridinium (MPP⁺) and dopaminergic (DA) neurons in the substantia nigra (SN) against 1-methyl-4-phenyl-1,2,3,6-tetra-hydropyridine (MPTP) toxicity. Western blot and immunohistochemical analysis showed that, unlike SAG, Tat-SAG transduced efficiently into SH-SY5Y cells and into the brain, respectively. Tat-SAG remarkably suppressed ROS generation, DNA damage, and the progression of apoptosis, caused by MPP⁺ in SH-SY5Y cells. Also, immunohistochemical data using a tyrosine hydroxylase antibody and cresyl violet staining demonstrated that Tat-SAG obviously protected DA neurons in the SN against MPTP toxicity in a PD mouse model. Tat-SAG-treated mice showed significant enhanced motor activities, compared to SAG- or Tat-treated mice. Therefore, our results suggest that Tat-SAG has potential as a therapeutic agent against ROS-related diseases such as PD.     

Immunity of Fetal Mice to Prenatal Administration of the Dopaminergic Neurotoxin 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine

Abstract: Subcutaneous injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) HC1 (25 mg/kg) in pregnant female mice at the 17th day of gestation markedly depleted striatal dopamine (DA) concentrations in the mothers 24 h later and at 24 h and 28 days after delivery. By contrast, in the offspring of the female mice exposed to MPTP during pregnancy, fetal brain DA concentrations at 24 h after injection and at 24 h after birth and striatal DA levels at 14 and 28 days postnatally were unaffected and identical to those in age-matched controls. The postnatal ontogenesis of striatal DA levels was identical in offspring of control vehicle- and MPTP-treated pregnant mice. Also, prenatal challenge with MPTP did not make nigrostriatal DA neurons more vulnerable to a second postnatal treatment with the toxin. Striatal DA depletions were identical in 6-week-old mice given MPTP, whether they were exposed to MPTP or to vehicle in utero. Monoamine oxidase (EC 1.4.3.4; MAO) type B activity was extremely low in the fetal brain and, relatively, much lower than that of MAO-A. Prenatal MPTP administration reduced maternal striatal and also embryonal brain MAO-B activity at 24 h post treatment but did not alter the normal postnatal development of striatal MAO-A and -B activities in the offspring. Study suggests that resistance of fetal DA neurons to the DA-depleting effect of MPTP may be due, at least in part, to an absence in the embryonal brain of adequately developed MAO-B activity required for the conversion of MPTP to its toxic metabolite, 1-methyl-4-phenylpyridinium ion.