The perivascular pathways for influx of cerebrospinal fluid are most efficient in the midbrain.

Although there are no conventional lymphatic vessels in the brain, fluid and solutes drain along basement membranes (BMs) of cerebral capillaries and arteries towards the subarachnoid space and cervical lymph nodes. Convective influx/glymphatic entry of the cerebrospinal fluid (CSF) into the brain parenchyma occurs along the pial-glial BMs of arteries. This project tested the hypotheses that pial-glial BM of arteries are thicker in the midbrain, allowing more glymphatic entry of CSF. The in vivo MRI and PET images were obtained from a 4.2-year-old dog, whereas the post-mortem electron microscopy was performed in a 12-year-old dog. We demonstrated a significant increase in the thickness of the pial-glial BM in the midbrain compared with the same BM in different regions of the brain and an increase in the convective influx of fluid from the subarachnoid space. These results are highly significant for the intrathecal drug delivery into the brain, indicating that the midbrain is better equipped for convective influx/glymphatic entry of the CSF.

Atrazine Causes Autophagy- and Apoptosis-Related Neurodegenerative Effects in Dopaminergic Neurons in the Rat Nigrostriatal Dopaminergic System.

Atrazine (2-chloro-4-ethytlamino-6-isopropylamine-1,3,5-triazine; ATR) is widely used as a broad-spectrum herbicide. Animal studies have demonstrated that ATR exposure can cause cell death in dopaminergic neurons. The molecular mechanisms underlying ATR-induced neuronal cell death, however, are unknown. In this study, we investigated the autophagy and apoptosis induced by ATR in dopaminergic neurons in vivo. Wistar rats were administered with ATR at doses of 10, 50 and 100 mg/kg body weight by oral gavage for three months. In terms of histopathology, the expression of autophagy- and apoptosis-related genes as well as proteins related to the Beclin-1/B-cell lymphoma 2 (Bcl-2) autophagy and apoptosis pathways were examined in the rat nigrostriatal dopaminergic system. We observed degenerative micromorphology indicative of neuronal apoptosis and mitochondrial autophagy by electron microscopy in ATR-exposed rat striatum. The rat ventral mesencephalon in the ATR-exposed groups also showed increased expression of Beclin-1, LC3-II, Bax and Caspase-9, and decreased expression of tyrosine hydroxylase (TH), Bcl-xl and Bcl-2. These findings indicate that ATR may induce autophagy- and apoptosis-related changes in doparminergic neurons. Furthermore, this induction may be regulated by the Beclin-1 and Bcl-2 autophagy and apoptosis pathways, and this may help to better understand the mechanism underlying the neurotoxicity of ATR.

[Organization of the projections of the substructures of deep mesencephalic nucleus to the striatum in the dog brain].

Method of retrograde axonal transport of horseradish peroxidase was used to study the organization of the projections of the individual substructures of the deep mesencephalic nucleus complex to the functionally diverse regions of striatal structures of the dog brain (n=20). It was shown that the projection fibers of the neurons of the nucleus profundus mesencephali were directed to the ventro-lateral segment of the nucleus caudatus and the ventral segment of the putamen. The dorsal segment of the putamen obtains the fibers from the neurons of the nucleus cuneiformis, while the lateral segment of the nucleus accumbens received them from the neurons of the nucleus subcuneiformis. The possible pathways for conduction of the functionally diverse information and its integration in the investigated projection systems are discussed.

Single-cell brain atlas of Parkinson's disease mouse model.

Parkinson's disease (PD) is a neurodegenerative disease, leading to the impairment of movement execution. PD pathogenesis has been largely investigated, either limited to bulk transcriptomic levels or at certain cell types, which failed to capture the cellular heterogeneity and intrinsic interplays among distinct cell types. Here, we report the application of single-nucleus RNA-seq on midbrain, striatum, and cerebellum of the α-syn-A53T mouse, a well-established PD mouse model, and matched controls, generating the first single cell transcriptomic atlas for the PD model mouse brain composed of 46,174 individual cells. Additionally, we comprehensively depicte the dysfunctions in PD pathology, covering the elevation of NF-κB activity, the alteration of ion channel components, the perturbation of protein homeostasis network, and the dysregulation of glutamatergic signaling. Notably, we identify a variety of cell types closely associated with PD risk genes. Taken together, our study provides valuable resources to systematically dissect the molecular mechanism of PD pathogenesis at the single-cell resolution, which facilitates the development of novel approaches for diagnosis and therapies against PD.

Neurog2 directly converts astrocytes into functional neurons in midbrain and spinal cord.

Conversion of astrocytes into neurons in vivo offers an alternative therapeutic approach for neuronal loss after injury or disease. However, not only the efficiency of the conversion of astrocytes into functional neurons by single Neurog2, but also the conundrum that whether Neurog2-induced neuronal cells (Neurog2-iNs) are further functionally integrated into existing matured neural circuits remains unknown. Here, we adopted the AAV(2/8) delivery system to overexpress single factor Neurog2 into astrocytes and found that the majority of astrocytes were successfully converted into neuronal cells in multiple brain regions, including the midbrain and spinal cord. In the midbrain, Neurog2-induced neuronal cells (Neurog2-iNs) exhibit neuronal morphology, mature electrophysiological properties, glutamatergic identity (about 60%), and synapse-like configuration local circuits. In the spinal cord, astrocytes from both the intact and lesioned sources could be converted into functional neurons with ectopic expression of Neurog2 alone. Notably, further evidence from our study also proves that Neurog2-iNs in the intact spinal cord are capable of responding to diverse afferent inputs from dorsal root ganglion (DRG). Together, this study does not merely demonstrate the feasibility of Neurog2 for efficient in vivo reprogramming, it gives an indication for the Neurog2-iNs as a functional and potential factor in cell-replacement therapy.

Short-latency visual input to the subthalamic nucleus is provided by the midbrain superior colliculus.

The subthalamic nucleus (STN) is one of the principal input nuclei of the basal ganglia. Using electrophysiological techniques in anesthetized rats, we show that the STN becomes responsive to visual stimuli at short latencies when local disinhibitory injections are made into the midbrain superior colliculus (SC), an important subcortical visual structure. Significantly, only injections into the lateral, but not medial, deep layers of the SC were effective. Corresponding disinhibition of primary visual cortex also was ineffective. Complementary anatomical analyses revealed a strong, regionally specific projection from the deep layers of the lateral SC to neurons in rostral and dorsal sectors of the STN. Given the retinocentric organization of the SC, these results suggest that lower-field stimuli represented in the lateral colliculus have a direct means of communicating with the basal ganglia via the STN that is not afforded to visual events occurring in the upper visual field.

Selective GABAergic control of higher-order thalamic relays.

GABAergic signaling is central to the function of the thalamus and has been traditionally attributed primarily to the nucleus reticularis thalami (nRT). Here we present a GABAergic pathway, distinct from the nRT, that exerts a powerful inhibitory effect selectively in higher-order thalamic relays of the rat. Axons originating in the anterior pretectal nucleus (APT) innervated the proximal dendrites of relay cells via large GABAergic terminals with multiple release sites. Stimulation of the APT in an in vitro slice preparation revealed a GABA(A) receptor-mediated, monosynaptic IPSC in relay cells. Activation of presumed single APT fibers induced rebound burst firing in relay cells. Different APT neurons recorded in vivo displayed fast bursting, tonic, or rhythmic firing. Our data suggest that selective extrareticular GABAergic control of relay cell activity will result in effective, state-dependent gating of thalamocortical information transfer in higher-order but not in first-order relays.

Light and electron microscopic localization of alpha-1 adrenergic receptor immunoreactivity in the rat striatum and ventral midbrain.

Electrophysiological and pharmacological studies have demonstrated that alpha-1 adrenergic receptor (alpha1AR) activation facilitates dopamine (DA) transmission in the striatum and ventral midbrain. However, because little is known about the localization of alpha1ARs in dopaminergic regions, the substrate(s) and mechanism(s) underlying this facilitation of DA signaling are poorly understood. To address this issue, we used light and electron microscopy immunoperoxidase labeling to examine the cellular and ultrastructural distribution of alpha1ARs in the caudate putamen, nucleus accumbens, ventral tegmental area, and substantia nigra in the rat. Analysis at the light microscopic level revealed alpha1AR immunoreactivity mainly in neuropil, with occasional staining in cell bodies. At the electron microscopic level, alpha1AR immunoreactivity was found primarily in presynaptic elements, with scarce postsynaptic labeling. Unmyelinated axons and about 30-50% terminals forming asymmetric synapses contained the majority of presynaptic labeling in the striatum and midbrain, while in the midbrain a subset of terminals forming symmetric synapses also displayed immunoreactivity. Postsynaptic labeling was scarce in both striatal and ventral midbrain regions. On the other hand, only 3-6% of spines displayed alpha1AR immunoreactivity in the caudate putamen and nucleus accumbens. These data suggest that the facilitation of dopaminergic transmission by alpha1ARs in the mesostriatal system is probably achieved primarily by pre-synaptic regulation of glutamate and GABA release.

Isolation and characterization of postsynaptic densities from various brain regions: enrichment of different types of postsynaptic densities.

Postsynaptic densities (PSDs) have been isolated from cerebral cortex, midbrain, cerebellum, and brain stem by the Triton X-100 method previously used in the isolation of cerebral PSDs (Cohen et al., 1977, J. Cell Biol. 74:181). These PSDs have been compared in protein composition, protein phosphorylation, and morphology. Thin-section electron microscopy revealed that cerebral cortex and midbrain PSDs were identical, being approximately 57 nm thick and composed of apparent aggregates 20-30 nm in diameter. Isolated cerebellar PSDs appeared thinner (33 nm) than cerebral cortex PSDs and lacked the apparent 20- to 30-nm aggregates, but had a latticelike structure. In unidirectional and rotary-shadowed replicas, the cerebrum and midbrain PSDs were circular in shape with a large central perforation or hole in the center of them. Cerebellum PSDs did not have a large perforation, but did have numerous smaller perforations in a lattice like structure. Filaments (6-9 nm) were observed connecting possible 20- to 30-nm aggregates in cerebrum PSDs and were also observed radiating from one side of the PSD. Both cerebral cortex and midbrain PSDs exhibited identical protein patterns on SDS gel electrophoresis. In comparison, cerebellar PSDs (a) lacked the major 51,000 Mr protein, (b) contained two times less calmodulin, and (c) contained a unique protein at 73,000 Mr. Calcium plus calmodulin stimulated the phosphorylation of the 51,000 and 62,000 Mr bands in both cerebral cortex and midbrain PSDs. In cerebellar PSDs, only the 58,000 and 62,000 Mr bands were phosphorylated. In the PSDs from all brain regions, cAMP stimulated the phosphorylation of Protein Ia (73,000 Mr), Protein Ib (68.000 Mr), and a 60,000 Mr protein, although cerebrum and midbrain PSDs contained very much higher levels of phosphorylated protein than did the cerebellum. On the basis of the morphological criteria, it is possible that PSDs isolated from cerebrum and midbrain were derived from the Gray type I, or asymmetric, synapses, whereas cerebellum PSDs were derived from the Gray type II, or symmetric, synapses. Since there is some evidence that the type I synapses are involved in excitatory mechanisms while the type II are involved in inhibitory mechanisms, the role of the PSD and of some of its proteins in these synaptic responses is discussed.

J1/tenascin in substrate-bound and soluble form displays contrary effects on neurite outgrowth.

The influence of J1/tenascin adsorbed to polyornithine-conditioned plastic (substrate-bound J1/tenascin) and J1/tenascin present in the culture medium (soluble J1/tenascin) on neurite outgrowth was studied with cultured single cells from hippocampus and mesencephalon of embryonic rats. Neurons at low density grew well on J1/tenascin substrates and extended neurites that were approximately 40% longer than on the polyornithine control substrate after 24 h in vitro. The neurite outgrowth promoting effect of substrate bound J1/tenascin was largely abolished in the presence of mAb J1/tn2, but not by mAb J1/tn1. In contrast to the neurite growth-promoting effects of substrate bound J1/tenascin, neurite outgrowth on polyornithine, laminin, fibronectin, or J1/tenascin as substrates was inhibited by addition of soluble J1/tenascin to the cultures. Neither of the two mAbs neutralized the neurite outgrowth-inhibitory properties of soluble J1/tenascin. In contrast to their opposite effects on neurite outgrowth, both substrate-bound and soluble J1/tenascin reduced spreading of the neuronal cell bodies, suggesting that the neurite outgrowth-promoting and antispreading effects are mediated by two different sites on the molecule. This was further supported by the inability of the mAb J1/tn2 to neutralize the antispreading effect. The J1/tn2 epitope localizes to a fibronectin type III homology domain that is presumably distinct from the putative Tn68 cell-binding domain of chicken tenascin for fibroblasts, as shown by electronmicroscopic localization of antibody binding sites. We infer from these experiments that J1/tenascin contains a neurite outgrowth promoting domain that is distinguishable from the cell-binding site and presumably not involved in the inhibition of neurite outgrowth or cell spreading. Our observations support the notion that J1/tenascin is a multifunctional extracellular matrix molecule.

Lewy pathology in Parkinson's disease consists of crowded organelles and lipid membranes.

Parkinson's disease, the most common age-related movement disorder, is a progressive neurodegenerative disease with unclear etiology. Key neuropathological hallmarks are Lewy bodies and Lewy neurites: neuronal inclusions immunopositive for the protein α-synuclein. In-depth ultrastructural analysis of Lewy pathology is crucial to understanding pathogenesis of this disease. Using correlative light and electron microscopy and tomography on postmortem human brain tissue from Parkinson's disease brain donors, we identified α-synuclein immunopositive Lewy pathology and show a crowded environment of membranes therein, including vesicular structures and dysmorphic organelles. Filaments interspersed between the membranes and organelles were identifiable in many but not all α-synuclein inclusions. Crowding of organellar components was confirmed by stimulated emission depletion (STED)-based super-resolution microscopy, and high lipid content within α-synuclein immunopositive inclusions was corroborated by confocal imaging, Fourier-transform coherent anti-Stokes Raman scattering infrared imaging and lipidomics. Applying such correlative high-resolution imaging and biophysical approaches, we discovered an aggregated protein-lipid compartmentalization not previously described in the Parkinsons' disease brain.

Floor plate chemoattracts crossed axons and chemorepels uncrossed axons in the vertebrate brain.

In the bilaterally symmetrical vertebrate CNS, all developing axons must choose between remaining on the same side of the midline or growing across it. The mechanism underlying this axonal pathfinding is, however, poorly understood. Here we demonstrate that the ventral midline floor plate (FP) chemorepels two types of ipsilaterally projecting axons, one from the alar plate and another from the basal plate in the mesencephalon. We further demonstrate that the FP chemoattracts contralaterally projecting myelencephalic as well as metencephalic axons. The FP at all axial levels displayed both chemoattractive and chemorepellent activities, suggesting that FP chemoattraction and chemorepulsion may be at work throughout the neuraxis. Chemotropic guidance by the FP may therefore play a key role in the establishment of neuronal projection laterality.

Guidance of circumferentially growing axons by netrin-dependent and -independent floor plate chemotropism in the vertebrate brain.

Netrin-1, a diffusible signal secreted by floor plate cells at the ventral midline of the vertebrate CNS, can attract ventrally migrating axons and repel a subset of dorsally migrating axons in the spinal cord and rostral hindbrain in vitro. Whether netrin-1 can act as a global cue to guide all circumferentially migrating axons is, however, unknown. Here, we show that netrin-1 can attract alar plate axons that cross the floor plate along its entire rostrocaudal axis. Dorsally directed axons forming the posterior commissure are, however, repelled by the floor plate by a netrin-independent mechanism. These results suggest that netrin-1 functions as a global guidance cue for attraction to the midline. Moreover, floor plate-mediated chemorepulsion may also operate generally to direct dorsal migrations, but its molecular basis may involve both netrin-dependent and -independent mechanisms.

Dynorphin-A immunoreactive terminals on the neuronal somata of rat mesencephalic trigeminal nucleus.

Dynorphin-A-like immunoreactivity was investigated in the rat mesencephalic trigeminal nucleus (Mes 5) at the light and electron microscopic levels. Dynorphin-A immunoreactive fibers and puncta, likely representing nerve terminals, were observed throughout rostrocaudal extension of the Mes 5 at the light microscopic level. Within the rostrocaudal extension, more abundant fibers and puncta were localized in the midbrain-pontine junction and pontine areas than in the midbrain area. At the electron microscopic level, dynorphin-A immunoreactive synapses were observed on the somata of Mes 5. Dynorphin-A-like immunoreactivity tended to be restricted to dense-cored vesicles in the synapses. These results suggest that dynorphin-A-containing fiber systems affect mastication through the Mes 5.

Normal biogenesis and cycling of empty synaptic vesicles in dopamine neurons of vesicular monoamine transporter 2 knockout mice.

The neuronal isoform of vesicular monoamine transporter, VMAT2, is responsible for packaging dopamine and other monoamines into synaptic vesicles and thereby plays an essential role in dopamine neurotransmission. Dopamine neurons in mice lacking VMAT2 are unable to store or release dopamine from their synaptic vesicles. To determine how VMAT2-mediated filling influences synaptic vesicle morphology and function, we examined dopamine terminals from VMAT2 knockout mice. In contrast to the abnormalities reported in glutamatergic terminals of mice lacking VGLUT1, the corresponding vesicular transporter for glutamate, we found that the ultrastructure of dopamine terminals and synaptic vesicles in VMAT2 knockout mice were indistinguishable from wild type. Using the activity-dependent dyes FM1-43 and FM2-10, we also found that synaptic vesicles in dopamine neurons lacking VMAT2 undergo endocytosis and exocytosis with kinetics identical to those seen in wild-type neurons. Together, these results demonstrate that dopamine synaptic vesicle biogenesis and cycling are independent of vesicle filling with transmitter. By demonstrating that such empty synaptic vesicles can cycle at the nerve terminal, our study suggests that physiological changes in VMAT2 levels or trafficking at the synapse may regulate dopamine release by altering the ratio of fillable-to-empty synaptic vesicles, as both continue to cycle in response to neural activity.

Therapeutic efficacy of olfactory stem cells in rotenone induced Parkinsonism in adult male albino rats.

BACKGROUND: Olfactory stem cells (OSCs) are found in the olfactory mucosa and olfactory bulb and have the capacity to proliferate and differentiate along multiple tissue lineages. Rotenone; widely used insecticide has a neurodegenerative effect on the dopaminergic cells of substantia nigra (SN) of midbrain producing Parkinsonism. The aim of this study is to isolate rat OSCs from olfactory mucosa and olfactory bulb, culture these OSCs in suitable medium to allow for their proliferation to be used in the treatment of Parkinsonism induced by rotenone. METHODS: The characteristics of OSCs, the effects of rotenone on the SN of midbrain and the curative effect of OSCs on the substantia nigra were determined morphologically, immunohistochemically, and by transmission electron microscopy. PKH 26; immunofluorescent dye was used as a cell tracer to locate the transplanted cells in host midbrain. RESULTS: OSCs were spindle shaped with irregular processes, and were positive for CD44 and Nestin and negative for CD34. Subcutaneous rotenone produced Parkinsonism through producing degeneration of the dopaminergic cells of SN of the midbrain. Transplantation of OSCs produced restoration of the normal structure of SN and dopaminergic cells and improves the clinical manifestations of Parkinsonism. CONCLUSION: These results indicate that, the isolated rat OSCs can proliferate and expand in vitro when culture in suitable medium and these cells can exert therapeutic effects in Parkinsonism by recruitment in SN and restoration of the structure and function of dopaminergic cells.

Existence of high and low affinity dinucleotides pentaphosphate-induced calcium responses in individual synaptic terminals and lack of correlation with the distribution of P2X1-7 subunits.

Individual analysis of synaptic terminals calcium responses, induced by dinucleotides pentaphosphate, Ap(5)A or Gp(5)G, demonstrates the presence of two main groups considering the concentration required for stimulation. The first group corresponds to those responding to Ap(5)A or Gp(5)G at nanomolar concentration, representing 16% and 12%, respectively, and the second one responds to micromolar concentration and represents, respectively, 17% and 14%, of the total functional synaptosomal population in rat midbrain. Dose-response curves in single terminals showed an Ap(5)A EC(50) values of 0.9+/-0.2 nM and 11.8+/-0.9 microM, being the maximal intrasynaptosomal calcium increase of 200+/-0.3 and 125+/-0.2 nM for the high and low affinity responding terminals, respectively. Combination of microfluorimetric and immunocytochemical studies showed lack of correlation between dinucleotides pentaphosphate responses and P2X receptor subunits expression, in spite of the abundance of P2X(2), P2X(3) and P2X(7) at the presynaptic level in rat midbrain synaptosomes. Pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), a P2X receptors antagonist, showed no effect on low affinity dinucleotides receptors population, and partial inhibition on the high affinity one. On the other hand, diinosine pentaphosphate (Ip(5)I) completely abolished the low affinity dinucleotides responses, and 60% inhibition of the high affinity ones.

Localization of alpha-synuclein to mitochondria within midbrain of mice.

The interrelationship between alpha-synuclein (alpha-syn) and mitochondria is not clearly understood. Owing to the lack of the signal peptide and its predominant localization in the cytosol, alpha-syn is generally considered to affect mitochondrial function through some secondary effects. Contrary to this assumption, here, we show that a portion of alpha-syn is present in the membrane of mitochondria in normal dopaminergic neurons. The same profile is also found in other alpha-syn-positive neurons. Thus, binding to the membrane of mitochondria is the physiological nature of alpha-syn and might also contribute to the pathological role of this protein in the mitochondrial dysfunction in Parkinson's disease.

Fine ultrastructure and biochemistry of PC12 cells: a comparative approach to understand neurotoxicity.

The PC12 cell line is commonly used as a tool to understand the biochemical mechanisms underlying the physiology and degeneration of central dopamine neurons. Despite the broad use of this cell line, there are a number of points differing between PC12 cells and dopamine neurons in vivo which are missed out when translating in vitro data into in vivo systems. This led us to compare the PC12 cells with central dopamine neurons, aiming at those features which are predictors of in vivo physiology and degeneration of central dopamine neurons. We carried out this comparison, either in baseline conditions, following releasing or neurotoxic stimuli (i.e. acute or chronic methamphetamine), to end up with therapeutic agents which are suspected to produce neurotoxicity (l-DOPA). Although the neurotransmitter pattern of PC12 cells is close to dopamine neurons, ultrastructural morphometry demonstrates that, in baseline conditions, PC12 cells possess very low vesicles density, which parallels low catecholamine levels. Again, compartmentalization of secretory elements in PC12 cells is already pronounced in baseline conditions, while it is only slightly affected following catecholamine-releasing stimuli. This low flexibility is caused by the low ability of PC12 cells to compensate for sustained catecholamine release, due both to non-sufficient dopamine synthesis and poor dopamine storage mechanisms. This contrasts markedly with dopamine-containing neurons in vivo lending substance to opposite findings between these compartments concerning the sensitivity to a number of neurotoxins.

The proinflammatory cytokines interleukin-1beta and tumor necrosis factor-alpha activate serotonin transporters.

Proinflammatory cytokines and serotonergic homeostasis have both been implicated in the pathophysiology of major psychiatric disorders. We have demonstrated that activation of p38 mitogen-activated protein kinase (MAPK) induces a catalytic activation of the serotonin transporter (SERT) arising from a reduction in the SERT Km for 5-hydroxytryptamine (5-HT). As inflammatory cytokines can activate p38 MAPK, we hypothesized that they might also activate neuronal SERT. Indeed, Interleukin-1beta (IL-1beta) and tumor necrosis factor alpha (TNF-alpha) stimulated serotonin uptake in both the rat embryonic raphe cell line, RN46A, and in mouse midbrain and striatal synaptosomes. In RN46A cells, IL-1beta stimulated 5-HT uptake in a dose- and time-dependent manner, peaking in 20 min at 100 ng/ml. This was abolished by IL-1ra (20 ng/ml), an antagonist of the IL-1 receptor, and by SB203580 (5 microM), a p38 MAPK inhibitor. TNF-alpha also dose- and time-dependently stimulated 5-HT uptake that was only partially blocked by SB203580. Western blots showed that IL-1beta and TNF-alpha activated p38 MAPK, in an SB203580-sensitive manner. IL-1beta induced an SB203580-sensitive decrease in 5-HT Km with no significant change in Vmax. In contrast, TNF-alpha stimulation decreased 5-HT Km and increased SERT Vmax. SB203580 selectively blocked the TNF-alpha-induced change in SERT Km. In mouse midbrain and striatal synaptosomes, maximal stimulatory effects on 5-HT uptake occurred at lower concentrations (IL-1beta, 10 ng/ml; TNF-alpha, 20 ng/ml), and over shorter incubation times (10 min). As with RN46A cells, the effects of IL-1beta and TNF-alpha were completely (IL-1beta) or partially (TNF-alpha) blocked by SB203580. These results provide the first evidence that proinflammatory cytokines can acutely regulate neuronal SERT activity via p38 MAPK-linked pathways.