Methamphetamine self-administration results in persistent dopaminergic pathology: implications for Parkinson's disease risk and reward-seeking.

Methamphetamine (Meth) abuse may be a risk factor for Parkinson's disease (PD); a problematic event as approximately 33 million people abuse Meth worldwide. The current study determined if a mild form of PD-like nigrostriatal pathology occurred following forced abstinence in Meth self-administering rats. The average daily intake of self-administered Meth was 3.6 ± 0.2 mg/kg/3 h over 14 sessions. Subsequently, animals were killed and the brains harvested at 1, 7, 28 or 56 days of abstinence. Post mortem, tyrosine hydroxylase (TH) immunostaining in the dorsal striatum progressively decreased throughout abstinence, reaching a 50% loss at 56 days. In the substantia nigra, there was marked reduction of TH+ cells, and Fluorogold (retrograde tracer) transport from the striatum to the nigra, at 28 and 56 days after Meth. Thus, Meth-induced progressive nigrostriatal damage occurred retrogradely, similar to PD pathology. The mesolimbic dopamine pathway [i.e. ventral tegmental area (VTA) and nucleus accumbens (NAc)], critical for Meth-induced reward, was also evaluated. TH immunostaining was decreased in the NAc-core at 28 and 56 days of forced abstinence, while staining in the dorsomedial NAc-shell was preserved. Accordingly, TH+ cell loss was evident in the lateral VTA, the origin of projections to the NAc-core, but not the medial VTA where NAc-shell projections originate. Thus, after Meth-taking ceased, a time-dependent, progressive degeneration occurred within nigrostriatal projections that eventually engulfed lateral mesolimbic projections. This pathological pattern is consistent with a trajectory for developing PD; therefore, these findings provide preclinical support for Meth abuse to increase vulnerability to developing PD.

Dopamine receptors and the persistent neurovascular dysregulation induced by methamphetamine self-administration in rats.

Recently abstinent methamphetamine (Meth) abusers showed neurovascular dysregulation within the striatum. The factors that contribute to this dysregulation and the persistence of these effects are unclear. The current study addressed these knowledge gaps. First, we evaluated the brains of rats with a history of Meth self-administration following various periods of forced abstinence. Micro-computed tomography revealed a marked reduction in vessel diameter and vascular volume uniquely within the striatum between 1 and 28 days after Meth self-administration. Microvessels showed a greater impairment than larger vessels. Subsequently, we determined that dopamine (DA) D2 receptors regulated Meth-induced striatal vasoconstriction via acute noncontingent administration of Meth. These receptors likely regulated the response to striatal hypoxia, as hypoxia inducible factor 1α was elevated. Acute Meth exposure also increased striatal levels of endothelin receptor A and decreased neuronal nitric oxide synthase. Collectively, the data provide novel evidence that Meth-induced striatal neurovascular dysregulation involves DA receptor signaling that results in vasoconstriction via endothelin receptor A and nitric oxide signaling. As these effects can lead to hypoxia and trigger neuronal damage, these findings provide a mechanistic explanation for the selective striatal toxicity observed in the brains of Meth-abusing humans.

Progression of intestinal permeability changes and alpha-synuclein expression in a mouse model of Parkinson's disease.

Parkinson's disease (PD) is a multifocal degenerative disorder for which there is no cure. The majority of cases are sporadic with unknown etiology. Recent data indicate that untreated patients with de novo PD have increased colonic permeability and that both de novo and premotor patients have pathological expression of α-synuclein (α-syn) in their colon. Both endpoints potentially can serve as disease biomarkers and even may initiate PD events through gut-derived, lipopolysaccharide (LPS)-induced neuronal injury. Animal models could be ideal for interrogating the potential role of the intestines in the pathogenesis of PD; however, few current animal models of PD encompass these nonmotor features. We sought to establish a progressive model of PD that includes the gastrointestinal (GI) dysfunction present in human patients. C57/BL6 mice were systemically administered one dose of either LPS (2.5 mg/kg) or saline and were sacrificed in monthly intervals (n = 5 mice for 5 months) to create a time-course. Small and large intestinal permeability was assessed by analyzing the urinary output of orally ingested sugar probes through capillary column gas chromatography. α-Syn expression was assessed by counting the number of mildly, moderately, and severely affected myenteric ganglia neurons throughout the GI tract, and the counts were validated by quantitative optical density measurements. Nigrostriatal integrity was assessed by tyrosine hydroxylase immunohistochemistry stereology and densitometry. LPS caused an immediate and progressive increase in α-syn expression in the large intestine but not in the small intestine. Intestinal permeability of the whole gut (large and small intestines) progressively increased between months 2 and 4 after LPS administration but returned to baseline levels at month 5. Selective measurements demonstrated that intestinal permeability in the small intestine remained largely intact, suggesting that gut leakiness was predominately in the large intestine. Phosphorylated serine 129-α-syn was identified in a subset of colonic myenteric neurons at months 4 and 5. Although these changes were observed in the absence of nigrostriatal degeneration, an abrupt but insignificant increase in brainstem α-syn was observed that paralleled the restoration of permeability. No changes were observed over time in controls. LPS, an endotoxin used to model PD, causes sequential increases in α-syn immunoreactivity, intestinal permeability, and pathological α-syn accumulation in the colon in a manner similar to that observed in patients with PD. These features are observed without nigrostriatal degeneration and incorporate PD features before the motor syndrome. This allows for the potential use of this model in testing neuroprotective and disease-modifying therapies, including intestinal-directed therapies to fortify intestinal barrier integrity.

Evidence for angiogenesis in Parkinson's disease, incidental Lewy body disease, and progressive supranuclear palsy.

Angiogenesis has not been extensively studied in Parkinson's disease (PD) despite being associated with other neurodegenerative disorders. Post-mortem human brain tissues were obtained from subjects with pathologically confirmed Parkinson's disease (PD) and progressive supranuclear palsy (PSP), a rapidly progressing Parkinsonian-like disorder. Tissues were also obtained from subjects with incidental Lewy body disease (iLBD) who had Lewy bodies in the substantia nigra pars compacta (SN(pc)) but had not been diagnosed with PD, and age-matched controls without Lewy body pathology. The SNpc, putamen, locus ceruleus (LC) and midfrontal cortex were examined for integrin αvß3, a marker for angiogenesis, along with vessel number and activated microglia. All parkinsonian syndromes had greater αvß3 in the LC and the SN(pc), while only PD and PSP subjects had elevated αvß3 in the putamen compared to controls. PD and PSP subjects also had increases in microglia number and activation in the SN(pc) suggesting a link between inflammation and clinical disease. Microglia activation in iLBD subjects was limited to the LC, an area involved at an early stage of PD. Likewise, iLBD subjects did not differ from controls in αvß3 staining in the putamen, a late area of involvement in PD. The presence of αvß3 reactive vessels in PD and its syndromes is indicative of newly created vessels that have not likely developed the restrictive properties of the blood brain barrier. Such angiogenic vessels could contribute to neuroinflammation by failing to protect the parenchyma from peripheral immune cells and inflammatory or toxic factors in the peripheral circulation.

The blood-brain barrier in neurodegenerative disease: a rhetorical perspective.

Recent studies suggest that the function of the blood-brain barrier (BBB) is not static under normal physiologic conditions and is likely altered in neurodegenerative disease. Prevailing thinking about CNS function, and neurodegenerative disease in particular, is neurocentric excluding the impact of factors outside the CNS. This review challenges this perspective and discusses recent reports suggesting the involvement of peripheral factors including toxins and elements of adaptive immunity that may not only play a role in pathogenesis, but also progression of neurodegenerative diseases. Central to this view is neuroinflammation. Several studies indicate that the neuroinflammatory changes that accompany neurodegeneration affect the BBB or its function by altering transport systems, enhancing immune cell entry, or influencing the BBB's role as a signaling interface. Such changes impair the BBB's normal homeostatic function and affect neural activity. Moreover, recent studies reveal that alterations in BBB and its transporters affect the entry of drugs used to treat neurodegenerative diseases. Incorporating BBB compromise and dysfunction into our view of neurodegenerative disease leads to the inclusion of peripheral mediators in its pathogenesis and progression. In addition, this changing view of the BBB raises interesting new therapeutic possibilities for drug delivery as well as treatment strategies designed to reinstate normal barrier function.

Evidence of angiogenic vessels in Alzheimer's disease.

Alterations in the blood brain barrier and brain vasculature may be involved in neurodegeneration and neuroinflammation. We sought to determine if vascular remodeling characterized by angiogenic vessels or increased vascular density, occurred in pathologically confirmed Alzheimer's disease (AD) postmortem human brain tissues. We examined brains of deceased, older catholic clergy from the Religious Order Study, a longitudinal clinical-pathological study of aging and AD. The hippocampus, midfrontal cortex, substantia nigra, globus pallidus and locus ceruleus were examined for integrin alphavbeta3 immunoreactivity, a marker of angiogenesis, and vascular densities. Activated microglia cell counts were also performed. All areas except the globus pallidus exhibited elevated alphavbeta3 immunoreactivity in AD cases compared with controls. Only in the hippocampus did the ongoing angiogenesis result in increased vascular density compared with controls. Vascular density was correlated with Abeta load in the hippocampus and alphavbeta3 reactivity was correlated with neurofibrillary tangles in the midfrontal cortex and in the substantia nigra. These data indicate that ongoing angiogenesis is present in brain regions affected by AD pathology and may be related to tissue injury.

Neuroinflammation and peripheral immune infiltration in Parkinson's disease: an autoimmune hypothesis.

Despite decades of research and the development of a large group of animal models, our understanding of the mechanisms responsible for the progressive loss of dopamine neurons in Parkinson's disease (PD) is unknown. So-called neuroprotective studies demonstrate that a vast group of molecules readily attenuate the dopamine (DA) neuron loss produced by DA neurotoxin insult. Despite these successes, these neuroprotective strategies have been surprisingly ineffective in patients. This may reflect the fact that the initial pathogenic event and the subsequent disease progression is a consequence of different mechanisms. As we began to think about this disconnect, we discovered that animals exposed to DA neurotoxins exhibited blood-brain barrier (BBB) dysfunction. If the BBB in PD patients is disrupted, then the barrier that normally segregates peripheral vascular factors from brain parenchyma is no longer present. Immune cells could then enter brain and produce a self-perpetuating (progressive) degenerative process. In this review, we propose that peripheral immunity contributes to the degenerative process of PD and may be responsible for the progressive nature of the disease. This hypothesis is supported by a broad and diverse literature that is just beginning to come together to suggest that PD is, in part, an autoimmune disease. In order to understand this hypothesis, the reader must question the conventional wisdom that the BBB is intact in PD, the brain is an immune privileged area, and that pathogenic insult and disease progression may reflect different mechanisms.

Altered glutathione homeostasis in animals prenatally exposed to lipopolysaccharide.

We previously reported that injection of bacterial lipopolysaccharide (LPS) into gravid female rats at embryonic day 10.5 resulted in a birth of offspring with fewer than normal dopamine (DA) neurons along with innate immunity dysfunction and many characteristics seen in Parkinson's disease (PD) patients. The LPS-exposed animals were also more susceptible to secondary toxin exposure as indicated by an accelerated DA neuron loss. Glutathione (GSH) is an important antioxidant in the brain. A disturbance in glutathione homeostasis has been proposed for the pathogenesis of PD. In this study, animals prenatally exposed to LPS were studied along with an acute intranigral LPS injection model for the status of glutathione homeostasis, lipid peroxidation, and related enzyme activities. Both prenatal LPS exposure and acute LPS injection produced a significant GSH reduction and increase in oxidized GSH (GSSG) and lipid peroxide (LPO) production. Activity of gamma-glutamylcysteine synthetase (GCS), the rate-limiting enzyme in de novo GSH synthesis, was up-regulated in acute supranigral LPS model but was reduced in the prenatal LPS model. The GCS light subunit protein expression was also down-regulated in prenatal LPS model. GSH redox recycling enzyme activities (glutathione peroxidase, GPx and glutathione reducdase, GR) and glutathione-S-transferase (GST), gamma-glutamyl transpeptidase (gamma-GT) activities were all increased in prenatal LPS model. Prenatal LPS exposure and aging synergized in GSH level and GSH-related enzyme activities except for those (GR, GST, and gamma-GT) with significant regional variations. Additionally, prenatal LPS exposure produced a reduction of DA neuron count in the substantia nigra (SN). These results suggest that prenatal LPS exposure may cause glutathione homeostasis disturbance in offspring brain and render DA neurons susceptible to the secondary neurotoxin insult.

Blood-brain barrier pathology in Alzheimer's and Parkinson's disease: implications for drug therapy.

The blood-brain barrier (BBB) is a tightly regulated barrier in the central nervous system. Though the BBB is thought to be intact during neurodegenerative diseases such as Alzheimer's (AD) and Parkinson's disease (PD), recent evidence argues otherwise. Dysfunction of the BBB may be involved in disease progression, eliciting of peripheral immune response, and, most importantly, altered drug efficacy. In this review, we will give a brief overview of the BBB, its components, and their functions. We will critically evaluate the current literature in AD and PD BBB pathology resulting from insult, neuroinflammation, and neurodegeneration. Specifically, we will discuss alterations in tight junction, transport and endothelial cell surface proteins, and vascular density changes, all of which result in altered permeability. Finally, we will discuss the implications of BBB dysfunction in current and future therapeutics. Developing a better appreciation of BBB dysfunction in AD and PD may not only provide novel strategies in treatment, but will prove an interesting milestone in understanding neurodegenerative disease etiology and progression.

Progressive dopamine neuron loss in Parkinson's disease: the multiple hit hypothesis.

Animal models have been an essential tool for researchers and clinicians in their efforts to study and treat Parkinson's disease (PD). Thus, the various ways 6-hydroxydopamine is employed, the use of MPTP in rodents and nonhuman primates, the prenatal exposure to bacterial endotoxin, the postnatal exposure to environmental toxins such as paraquat and rotenone, the assessment of dopamine (DA) neurons in genetic knockout mouse, and even the behavioral analysis of fruit flies and worms have added significantly to our knowledge base of PD--or have they? Are these animal models manifesting a true model of PD? Have the 7786 published studies (to date) on PD with animal models led to a clearer understanding of its etiology, treatment, or progression? In this review we critically assess this question. We begin with a succinct history of the major contributions, which have led to the current animal models of PD. We then evaluate the primary issue of the progressive loss of DA neurons, which, except for a few studies, has not been addressed in animal models of PD, even though this is the major pathological characteristic of the disease. Lastly, we discuss the possibility that more than one risk factor for PD may be necessary to develop an animal model that shows synergy--the progressive loss of DA neurons. Thus, the multiple hit hypothesis of PD-that is, the effect of more then one risk factor-may be the start of new era in animal models of PD that is one step closer to mimicking the pathology of PD in humans.

Age-related changes in glutathione and glutathione-related enzymes in rat brain.

The most reliable and robust risk factor for some neurodegenerative diseases is aging. It has been proposed that processes of aging are associated with the generation of reactive oxygen species and a disturbance of glutathione homeostasis in the brain. Yet, aged animals have rarely been used to model the diseases that are considered to be age-related such as Parkinson's or Alzheimer's disease. This suggests that the results from these studies would be more valuable if aged animals were used. The present study was designed to provide insight into the glutathione redox state in young and aged rat siblings of both genders by studying the enzyme activities related to glutathione synthesis, cycling, and usage. The results suggested a significant age-related reduction of reduced glutathione (GSH) level in all brain regions examined, associated with an increase of GSH oxidation to glutathione disulfide (GSSG) and decrease of the GSH/GSSG ratio. These changes were accompanied by diminished gamma-glutamylcysteine synthetase activity in de novo glutathione synthesis and increased lipid peroxidation. In addition, these changes were associated with increased enzyme activities related to the GSH usage (glutathione peroxidase, gamma-glutamyl transpeptidase, and glutathione S-transferase). The results indicate that aged animals are likely more vulnerable to oxidative stress and insinuate the roles of aged animals in modeling age-related neurodegeneration diseases.

Prenatal exposure to the bacteriotoxin lipopolysaccharide leads to long-term losses of dopamine neurons in offspring: a potential, new model of Parkinson's disease.

The cause of Parkinson's disease (PD) is currently unknown. Although a genetic cause has been implicated in familial PD, the vast majority of cases are considered idiopathic. Environmental toxins have been implicated as a cause for PD by many investigators. Unfortunately, the magnitude of this exposure would likely need to be very high and as a result, would likely have been identified by the many epidemiological studies performed to date. Recently, we inadvertently realized that exposure to neurotoxins while still in utero may also represent a risk factor. Thus, exposure to the bacteriotoxin, lipopolysaccharide (LPS) during a critical developmental window in rats, leads to the birth of animals with fewer than normal dopamine (DA) neurons. This DA neuron loss is apparently permanent as it is still present in 16 months old animals (the longest period studied to date). Moreover, the loss of DA neurons seen in these animals increases with age thereby mimicking the progressive pattern of cell loss seen in human PD. The DA neuron loss is accompanied by reductions in striatal DA, increases in DA activity, and increased production of the pro-inflammatory cytokine Tumor Necrosis Factor alpha (TNF-alpha). These are also characteristics of the PD brain. This model therefore shares many of the same characteristics with PD, and most importantly exhibits a slow, protracted loss of DA neurons - a characteristics of this animal model not found in other models. Interestingly, a common complication of pregnancy is a condition known as bacterial vaginosis (BV), which is known to produce increased levels of LPS and pro-inflammatory cytokines in the chorioamniotic environment of the fetus. This raises the interesting possibility that BV may be a risk factor for PD. The possibility that prenatal toxin exposure may contribute to the development of a neurodegenerative disease of the aged raises interesting new pathogenic questions and draws attention to the possibility that in utero exposure to neurotoxins may represent a here to fore unrecognized cause of PD.

Lipopolysaccharide (LPS)-induced dopamine cell loss in culture: roles of tumor necrosis factor-alpha, interleukin-1beta, and nitric oxide.

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the loss of dopamine (DA) neurons of the substantia nigra pars compacta (SNc). Although the exact mechanisms responsible for this cell loss are unclear, emerging evidence suggests the involvement of inflammatory events. In the present study, we characterized the effects of the proinflammatory bacteriotoxin lipopolysaccharide (LPS) on the number of tyrosine hydroxylase immunoreactive (THir) cells (used as an index for DA neurons) in primary mesencephalic cultures. LPS (10-80 microg/ml) selectively decreased THir cells and increased culture media levels of interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) as well as nitrite (an index of nitric oxide (NO) production). Cultures exposed to both LPS and neutralizing antibodies to IL-1beta or TNF-alpha showed an attenuation of the LPS-induced THir cell loss by at least 50% in both cases. Inhibition of the inducible form of nitric oxide synthase (iNOS) by L-NIL did not affect LPS toxicity, but increased the LPS-induced levels of both TNF-alpha and IL-1beta. These findings suggest that neuroinflammatory stimuli which lead to elevations in cytokines may induce DA neuron cell loss in a NO-independent manner and contribute to PD pathogenesis.

Prenatal cocaine exposure induces an attenuation of uterine blood flow in the rat.

We have previously demonstrated that maternal cocaine injections result in a gradient of fetal brain cocaine levels that decrease as a function of the fetuses' proximity to the ovaries at embryonic (E) day 15. Our prior data suggest that cocaine-induced vasoconstriction may (1) limit cocaine's entry into the brain and (2) cause damage to DA neurons through injury associated with hypoxia or ischemia of the utero-placental junction. Therefore, using the microsphere technique (labeled with Ru(103)), the following study sought to determine whether the previously observed pattern of cocaine distribution among fetuses in the uterus were due to position-specific reductions in uterine or placental blood flow. On day 15, a single subcutaneous injection of 30 mg/kg cocaine HCl was administered to each rat. Thirty minutes after the cocaine injection, reference blood samples were drawn from the ventral tail artery. Uterine segments and placentae were removed and subjected to gamma counting. While results regarding placental blood flow were equivocal, cocaine significantly reduced average uterine blood flow by 54.6%. In addition, as one moves more proximal to the ovaries, cocaine progressively attenuates blood flow in uterine tissue segments. These data support the hypothesis that the pattern of drug distribution and subsequent brain alterations from prenatal cocaine exposure in our previous reports are likely due to differences in uterine blood flow.

The effects of psychostimulant drugs on blood brain barrier function and neuroinflammation.

The blood brain barrier (BBB) is a highly dynamic interface between the central nervous system (CNS) and periphery. The BBB is comprised of a number of components and is part of the larger neuro(glio)vascular unit. Current literature suggests that psychostimulant drugs of abuse alter the function of the BBB which likely contributes to the neurotoxicities associated with these drugs. In both preclinical and clinical studies, psychostimulants including methamphetamine, MDMA, cocaine, and nicotine, produce BBB dysfunction through alterations in tight junction protein expression and conformation, increased glial activation, increased enzyme activation related to BBB cytoskeleton remodeling, and induction of neuroinflammatory pathways. These detrimental changes lead to increased permeability of the BBB and subsequent vulnerability of the brain to peripheral toxins. In fact, abuse of these psychostimulants, notably methamphetamine and cocaine, has been shown to increase the invasion of peripheral bacteria and viruses into the brain. Much work in this field has focused on the co-morbidity of psychostimulant abuse and human immunodeficiency virus (HIV) infection. As psychostimulants alter BBB permeability, it is likely that this BBB dysfunction results in increased penetration of the HIV virus into the brain thus increasing the risk of and severity of neuro AIDS. This review will provide an overview of the specific changes in components within the BBB associated with psychostimulant abuse as well as the implications of these changes in exacerbating the neuropathology associated with psychostimulant drugs and HIV co-morbidity.

An angiogenic inhibitor, cyclic RGDfV, attenuates MPTP-induced dopamine neuron toxicity.

We previously demonstrated that several dopamine (DA) neurotoxins produced punctate areas of FITC-labeled albumin (FITC-LA) leakage in the substantia nigra and striatum suggesting blood brain barrier (BBB) dysfunction. Further, this leakage was co-localized with αvß3 integrin up-regulation, a marker for angiogenesis. This suggested that the FITC-LA leakage might have been a result of angiogenesis. To assess the possible role of angiogenesis in DA neuron loss, we treated mice with 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine (MPTP) and on the following day treated with cyRGDfV, a cyclic peptide that binds to integrin αvß3 and prevents angiogenesis. Post-treatment for 3 days (b.i.d.) with cyRGDfV blocked the MPTP-induced upregulation of integrin ß3 immunoreactivity (a marker for angiogenesis), leakage of FITC-LA into brain parenchyma (a marker for BBB disruption) as well as the down regulation of Zona Occludin-1 (ZO-1; a marker for tight junction integrity). In addition, cyRGDfV also completely prevented tyrosine hydroxylase immunoreactive cell loss (a marker for DA neurons) and markedly attenuated the up-regulation of activated microglia (Iba1 cell counts and morphology). These data suggest that cyRGDfV, and perhaps other anti-angiogenic drugs, are neuroprotective following acute MPTP treatment and may suggest that compensatory angiogenesis and BBB dysfunction may contribute to inflammation and DA neuron loss.

Methamphetamine-induced vascular changes lead to striatal hypoxia and dopamine reduction.

Methamphetamine (meth) is a potent psychostimulant known to cause neurotoxicity. Clinical reports suggest meth abuse is a risk factor for Parkinson's disease. We investigated changes in the blood-brain barrier and cerebral vasculature as a mechanism underlying this risk in rats treated acutely and trained to self-administer meth. We observed blood-brain barrier leakage in rats treated acutely with meth. Hypoperfusion in the striatum was detected with acute and chronic meth treatment and was associated with hypoxia. This was correlated with reductions in striatal tyrosine hydroxylase in rats trained to self-administer meth. These findings suggest a new mechanism of meth-induced neurotoxicity involving striatal vasoconstriction resulting in hypoxia and dopamine reductions leading to an increased risk for Parkinson's disease for meth abusers.

Prenatal lipopolysaccharide does not accelerate progressive dopamine neuron loss in the rat as a result of normal aging.

We previously demonstrated that in utero exposure to the bacteriotoxin lipopolysaccharide (LPS) led to the birth of rat pups with fewer than normal dopamine (DA) neurons. These animals exhibited significant neuroinflammation in the nigrostriatal pathway creating the possibility that they could exhibit further, progressive DA neuron loss over their lives. To study this possibility, we injected gravid female rats i.p. at 10,000 endotoxin units (EUs) of LPS per kg or saline at embryonic (E) day 10.5 and assigned pups to sacrifice groups at 4, 14 and 17 months such that littermates were sacrificed at each end point. The effects of prenatal LPS on DA cell counts and striatal DA were significantly reduced relative to controls whereas DA activity and numbers of activated microglia (OX-6ir cell) were statistically increased. However, the progressive DA neuron loss was parallel to that of the controls suggesting that prenatal LPS does not produce an accelerated rate of DA neuron loss. Interestingly, locomotor activity was increased after 3 months in animals exposed to LPS prenatally, but by 16 months, was significantly reduced relative to controls. Additionally, animals exposed to LPS prenatally exhibited Lewy body-like inclusions that were first seen in 14 month old animals. These data broadly support previous studies demonstrating that prenatal exposure to LPS, as frequently occurs in humans as part of Bacterial Vaginosis, leads to the birth of animals with fewer than normal DA neurons. The progressive DA neuron loss seen in these animals is, however, primarily a result of normal aging.

Dopaminergic and serotoninergic deficiencies in young adult rats prenatally exposed to the bacterial lipopolysaccharide.

We have reported previously that prenatal bacterial lipopolysaccharide (LPS) exposure at the gestation window of vulnerability could consistently lead to dopamine (DA) neuron loss in the substantia nigra (SN). Thus, we suggested that prenatal LPS exposure might represent as a risk factor for the development of Parkinson's disease (PD). Here, we report that the same exposure could lead to tryptophan hydroxylase (TPH, a serotonin neuron marker) immunoreactive cell loss in the dorsal raphe nucleus (DRN). Twenty two pups born to saline or LPS-injected gravid female rats at E10.5 were used in the current study. Twelve male pups at age of 4 months (6 from each of two prenatal groups) were used for the tyrosine hydroxylase (TH) and tryptophan hydroxylase (TPH) immunochemistry studies. The other 10 (5 from each of two prenatal groups) males were used in the biochemistry studies. A 29% THir neuron loss in the substantia nigra (F(1,11)=17.573, P=0.002) and a 31% TPHir neuron loss (F(1,11)=44.005, P<0.001) in the DRN were seen. Significant DA and 5-hydroxytryptamine (5-HT) reductions (P<0.05) were found in the frontal cortex, nucleus accumbens, striatum, amygdala, hippocampus, and hypothalamus. The losses of DA and 5-HT were accompanied by the significant increases in homovanillic acid over DA and 5-hydroxyindoleacetic acid over 5-HT ratios in the most areas tested. These data further validate prenatal LPS exposure as a model of PD since DA and 5-HT changes similar to those seen in PD patients. They also suggest that prenatal LPS might be a risk factor for other diseases including mood disorders.