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Over the years, advances in immunohistochemistry techniques have been a critical step in detecting and mapping neuromodulatory substances in the central nervous system. The better quality and specificity of primary antibodies, new staining procedures and the spectacular development of imaging technologies have allowed such progress. Very recently, new methods permitting tissue transparency have been successfully used on brain tissues. In the present study, we combined whole-mount immunostaining for tyrosine hydroxylase (TH), oxytocin (OXT) and arginine vasopressin (AVP), with the iDISCO+ clearing method, light-sheet microscopy and semi-automated counting of three-dimensionally-labelled neurones to obtain a (3D) distribution of these neuronal populations in a 5-day postnatal (P5) mouse brain. Segmentation procedure and 3D reconstruction allowed us, with high resolution, to map TH staining of the various catecholaminergic cell groups and their ascending and descending fibre pathways. We show that TH pathways are present in the whole P5 mouse brain, similar to that observed in the adult rat brain. We also provide new information on the postnatal distribution of OXT and AVP immunoreactive cells in the mouse hypothalamus, and show that, compared to AVP neurones, OXT neurones in the supraoptic (SON) and paraventricular (PVN) nuclei are not yet mature in the early postnatal period. 3D semi-automatic quantitative analysis of the PVN reveals that OXT cell bodies are more numerous than AVP neurones, although their immunoreactive soma have a volume half smaller. More AVP nerve fibres compared to OXT were observed in the PVN and the retrochiasmatic area. In conclusion, the results of the present study demonstrate the utility and the potency of imaging large brain tissues with clearing procedures coupled to novel 3D imaging technologies to study, localise and quantify neurotransmitter substances involved in brain and neuroendocrine functions. [ABSTRACT FROM AUTHOR]

Dopaminergic neurons of the substantia nigra constitutively express the CXCR4 receptor for the chemokine stromal-cell-derived factor 1α (CXCL12) but, to date, no direct effect of CXCR4 activation by CXCL12 on membrane conductance of dopaminergic neurons has been demonstrated. We tested the effects of CXCL12 on whole-cell currents of dopaminergic neurons recorded in patch clamp in substantia nigra slices and showed that CXCL12 (0.01–10 nm) increased the amplitude of total high-voltage-activated (HVA) Ca currents through CXCR4 activation. This effect was reversibly reduced by ϖ-conotoxin-GVIA, suggesting that CXCL12 acted on N-type Ca currents, known to be involved in dopamine (DA) release. We therefore investigated the effects of CXCL12 on DA release from cultured dopaminergic neurons from the rat mesencephalon. In basal conditions, CXCL12 alone had no effect on DA release. When neurons were depolarized with KCl (20 mm), and thus when HVA Ca currents were activated, low CXCL12 concentrations (1–50 nm) increased DA release via CXCR4 stimulation. These data strongly suggest that the chemokine CXCL12 can act directly as a neuromodulator of dopaminergic neuronal electrical activity through the modulation of HVA currents. [ABSTRACT FROM AUTHOR]

We recently demonstrated that dopaminergic (DA) neurons of the rat substantia nigra constitutively expressed CXCR4, receptor for the chemokine stromal cell-derived factor-1 (SDF-1)/CXCL12 (SDF-1). To check the physiological relevance of such anatomical observation, in vitro and in vivo approaches were used. Patch clamp recording of DA neurons in rat substantia nigra slices revealed that SDF-1 (10 nmol/L) induced: (i) a depolarization and increased action potential frequency; and (ii) switched the firing pattern of depolarized DA neurons from a tonic to a burst firing mode. This suggests that SDF-1 could increase DA release from neurons. Consistent with this hypothesis, unilateral intranigral injection of SDF-1 (50 ng) in freely moving rat decreased DA content and increased extracellular concentrations of DA and metabolites in the ipsilateral dorsal striatum, as shown using microdialysis. Furthermore, intranigral SDF-1 injection induced a contralateral circling behavior. These effects of SDF-1 were mediated via CXCR4 as they were abrogated by administration of a selective CXCR4 antagonist. Altogether, these data demonstrate that SDF-1, via CXCR4, activates nigrostriatal DA transmission. They show that the central functions of chemokines are not restricted, as originally thought, to neuroinflammation, but extend to neuromodulatory actions on well-defined neuronal circuits in non-pathological conditions. [ABSTRACT FROM AUTHOR]

Pituitary adenylate cyclase-activating polypeptide (PACAP) was originally isolated from ovine hypothalamus on the basis of its hypophysiotrophic activity. It has subsequently been shown that PACAP and its receptors are widely distributed in the central nervous system of adult mammals, indicating that PACAP may act as a neurotransmitter and/or neuromodulator. It has also been found that PACAP and its receptors are expressed in germinative neuroepithelia, suggesting that PACAP could be involved in neurogenesis. There is now compelling evidence that PACAP exerts neurotrophic activities in the developing cerebellum and in embryonic stem (ES) cells. In particular, the presence of PACAP receptors has been demonstrated in the granule layer of the immature cerebellar cortex, and PACAP has been shown to promote survival, inhibit migration and activate neurite outgrowth of granule cell precursors. In cerebellar neuroblasts, PACAP is a potent inhibitor of the mitochondrial apoptotic pathway through activation of the MAPkinase extracellular regulated kinase. ES cells and embryoid bodies (EB) also express PACAP receptors and PACAP facilitates neuronal orientation and induces the appearance of an electrophysiological activity. Taken together, the anti-apoptotic and pro-differentiating effects of PACAP characterised in cerebellar neuroblasts as well as ES and EB cells indicate that PACAP acts not only as a neurohormone and a neurotransmitter, but also as a growth factor. [ABSTRACT FROM AUTHOR]

In rat substantia nigra (SN), Chemokine (CXC motif) receptor 4 (CXCR 4) for the chemokine stromal cell-derived factor (SDF)-1α is expressed on dopaminergic (DA) neurones, but also on non-DA cells, suggesting presynaptic actions. Using whole-cell patch-clamp recordings in DA neurones of rat SN slices at a holding potential of −60 mV, we showed here that SDF-1α exerts multiple presynaptic effects. First, SDF-1α (10 nm) induced an increase in the frequency of spontaneous and miniature GABAA postsynaptic currents by presynaptic mechanisms, consistent with the presence of CXCR4 on GABAergic neurones of the SN, as revealed by immunocytochemistry. Second, SDF-1α (0.1–1 nm) induced a glutamatergic inward current resistant to tetrodotoxin (TTX), most probably the result of glutamate release from non-neuronal cells. This inward current was not blocked by the CXCR4 antagonist AMD 3100 (1 µm), consistent with the lack of CXCR4 on astrocytes as shown by immunocytochemistry under basal conditions. Finally, SDF-1α (10 nm) induced, via CXCR4, an outward G protein-activated inward rectifier (GIRK) current, which was TTX sensitive and prevented by application of the GABAB antagonist CGP55845A, suggesting GABA spillover on to GABAB receptors. Our results show that SDF-1α induces, via presynaptic mechanisms, alterations in the excitability of DA neurones as confirmed by current-clamp experiments. [ABSTRACT FROM AUTHOR]

Recent studies demonstrated that the chemokine monocyte chemoattractant protein-1 (MCP-1)/CCL2 and its receptor, CCR2, play important roles in various brain diseases. In this study, using quantitative autoradiography, we studied the pharmacological properties of [[sup 125]I]MCP-1/CCL2 binding in rat brain and we clearly showed the distribution of CCR2 receptors in cerebral cortex, nucleus accumbens, striatum, amygdala, thalamus, hypothalamus, hippocampus, substantia nigra, mammillary bodies and raphe nuclei. Moreover, using double fluorescent immunohistochemistry, we showed that CCR2 receptors were constitutively expressed on neurons and astrocytes. Using RT-PCR methods, we demonstrated that CCR2 mRNA is present in various brain areas described above. Four hours after an acute intraperitoneal lipopolysaccharide injection, we showed that MCP-1/CCL2 binding was up-regulated in several brain structures; this effect took place on both CCR2B labelled neurons and astrocytes and to a lesser extent on activated microglia. To explore neurobiological function of CCR2, actimetric study was carried out. After intracerebroventricular injections of MCP-1/CCL2, we showed that motor activity was markedly decreased. Our results provide the first evidence for constitutive CCR2 receptor expression with precise neuroanatomical and cellular localizations in the brain, and its regulation during an inflammatory process, suggesting that MCP-1/CCL2 and CCR2 play important physiological and pathophysiological role(s) in the CNS. [ABSTRACT FROM AUTHOR]

Recent findings suggest that gonadal steroid hormones are neuroprotective and may provide clinical benefits in delaying the development of Parkinson's disease. In this report we investigated the ability of oestradiol to protect mesencephalic dopaminergic neurones cultured in serum-free or serum-supplemented medium from toxicity induced by 6-hydroxydopamine or 1-methyl-4-phenylpyridinium ion (MPP[sup +]). The efficiency of both toxins and oestradiol was evaluated by tyrosine hydroxylase (TH) immunocytochemistry, [[sup 3]H]dopamine ([[sup 3]H]DA) uptake, length of dopaminergic processes and␣lactate dehydrogenase (LDH) release measurement. In␣cultures grown in serum-supplemented medium, a 2-h pre-treatment with high concentrations (10–100 µm) of 17β-oestradiol or 17α-oestradiol, the stereoisomer with weak oestrogenic activity, protected both dopaminergic and non-dopaminergic neurones from toxicity induced by 6-hydroxydopamine (6-OHDA; 40 or 100 µm) and by the high MPP[sup +] concentrations (50 µm) necessary to obtain significant neuronal death under those culture conditions. At these concentrations, MPP[sup +] was no longer selective for dopaminergic neurones but affected all cells present in the culture. In contrast, the hormonal treatments did not protect against selective degeneration of dopaminergic neurones induced by lower MPP[sup +] concentrations (below 10 µm), related to inhibition of complex I of respiratory chain. In cultures grown in serum-free medium, oestradiol concentrations higher than 1 µm induced neuronal degeneration and no protection against 6-OHDA or MPP[sup +] toxicity was observed at lower concentrations of the steroid. The neuroprotective effects of 17α- or 17β-oestradiol evidenced in this model might be due to the antioxidant properties of these compounds. However, other non-genomic effects of the steroids cannot be excluded. [ABSTRACT FROM AUTHOR]

Plasma neurotensin (NT) was measured by radioimmunoassay in propanol extracted and unextracted plasma from 16 parkinsonian patients (four before treatment) and 16 age and sex matched controls. Mean plasma NT concentrations were consistently higher in parkinsonian patients than in controls and higher in the four untreated patients than in levodopa treated patients suggesting that plasma NT measurement may represent an easy detectable additional index in diagnosing parkinsonism and provides a novel approach to research in this field. [ABSTRACT FROM AUTHOR]

Purpose To investigate whether the chemokine CX3CL1 could play a role in the conjunctival inflammatory cell trafficking induced by an exposure to benzalkonium chloride (BAC). Methods Expression of CX3CL1 was assessed in BAC‐exposed human conjunctival cell (HCC)line using flow cytometry and RT‐PCR. In vitro migration of leukocytes to BAC‐stimulated HCCs was assessed by migration assays and immuno flow cytometry with or without inhibition of CX3CR1. In vivo inflammatory cell trafficking was investigated by immunohistochemistry and confocal microscopy in the conjunctiva of wild‐type or CX3CR1‐deficient mice exposed to BAC. Results BAC induced an overexpression of CX3CL1 in HCCs. Leukocyte chemotaxis was observed when HCCs are stimulated with BAC. Human monocytic cells (CD45+,CD14+) and NK cells (CD45+,CD56+) migration was inhibited by blocking the CXCR3 receptor. In a mouse model of BAC‐induced ocular surface toxicity, the inflammatory cell infiltration of the conjunctiva was altered in the CX3CR1‐deficient mice compared to wild‐type. Conclusion The CX3CL1/CX3CR1 axis is involved in the BAC‐induced conjunctival inflammation. Specific blockade of this receptor could regulate the cell trafficking in the ocular surface. [ABSTRACT FROM AUTHOR]