Cannabinoids exert pleiotropic actions in the CNS, including the inhibition of inflammatory responses and the enhancement of neuronal survival after injury. Although cannabinoid receptors are distributed widely in brain, their presence has not been investigated previously in oligodendrocytes. This study examined the expression of cannabinoid type 1 (CB1) receptors in rat oligodendrocytes in vivo and in culture and explored their biological function. Expression of CB1 receptors by oligodendrocytes was demonstrated immunocytochemically in postnatal and in adult white matter as well as in oligodendrocyte cultures. Reverse transcription-PCR and Western blotting further confirmed the presence of CB1 receptors. Oligodendrocyte progenitors undergo apoptosis with the withdrawal of trophic support, as determined by TUNEL assay and caspase-3 activation, and both the selective CB1 agonist arachidonyl-2'-chloroethylamide/(all Z)-N-(2-cycloethyl)-5,8,11,14-eicosatetraenamide (ACEA) and the nonselective cannabinoid agonists HU210 and (+)-Win-55212-2 enhanced cell survival. To investigate intracellular signaling involved in cannabinoid protection, we focused on the phosphatidylinositol-3 kinase (PI3K)/Akt pathway. HU210, (+)-Win-55212-2, and ACEA elicited a time-dependent phosphorylation of Akt. Pertussis toxin abolished Akt activation, indicating the involvement of G(i)/G(o)-protein-coupled receptors. The CB1 receptor antagonist SR141716A partially inhibited Akt phosphorylation in response to HU210 and (+)-Win-55212-2 and abolished the effects of ACEA. Trophic support deprivation downregulated Akt activity, and cannabinoids recovered phospho-Akt levels. Inhibition of PI3K abrogated the survival action and the recovery of Akt activity in response to cannabinoids. SR141716A prevented only the protection conferred by ACEA. Nevertheless, SR141716A and the selective CB2 receptor antagonist SR144528 in combination inhibited the prosurvival action of HU210, which is in accordance with the finding of CB2 receptor expression by oligodendroglial cells. These data identify oligodendrocytes as potential targets of cannabinoid action in the CNS.

Increasing evidence associates schizophrenia with prenatal exposure to infection. Impaired ability to "gate out" sensory and cognitive information is considered to be a central feature of schizophrenia and is manifested, among others, in disrupted prepulse inhibition (PPI) of the acoustic startle reflex. We analyzed the effect of a prenatal immune challenge-peripheral administration of bacterial endotoxin lipopolysaccharide (LPS) to pregnant female rats-upon PPI and immune function in adult offspring. Prenatal LPS treatment disrupted PPI which was reversed by antipsychotics. Serum levels of interleukin-2 and interleukin-6 were increased. In addition, histopathological features in brain areas related with PPI circuitry were observed. These results illustrate the critical influence of prenatal immune events upon adult CNS functioning in association with the putative role of the immune system in (Braff et al. 1978;Kumari et al. 1999). A well-established sensorimotor gating paradigm is the prepulse inhibition (PPI) of the startle response. PPI refers to the reduction in startle reactivity toward an intense pulse stimulus when it is shortly preceded by a weak prepulse stimulus (Hoffman and Ison 1980). It is thought that the prepulse response activates an inhibitory process that attenuates or "gates" the startle response. Because identical stimulus parameters can be used for animal and human studies, it is considered that animal models of PPI disruption represent a promising way to study the neural mechanisms underlying sensorimotor gating dysfunction (Swerdlow et al. 1994(Swerdlow et al. , 1999Swerdlow and Geyer 1998) and as a screening test for potential antipsychotics (Swerdlow et al. 1994;Depoortere et al. 1997). In fact, antipsychotics remove PPI deficits in schizophrenic patients (Kumari et al. 1999;Weike et al. 2000). Nevertheless, it must be taken into consideration that deficiency of PPI has been reported in other selected neuropsychiatric disorders where inability to inhibit movements is involved (Huntington's disease (Swerdlow et al. 1995 Tourette's syndrome (Castellanos et al. 1996)), where inability to control attentional and cognitive processes is involved (obsessive-compulsive disorder (Swerdlow et al. 1993)), or where anxiety and exaggerated startle occur (posttraumatic stress disorder (Grillon et al. 1996)). The focus of schizophrenia research has been turning from studies of structural and functional brain abnormalities to an increasing emphasis on possible etiologic factors. Neurodevelopmental theories of schizophrenia postulate that the psychopathology of schizophrenia may derive from alterations of brain organization secondary to defective ontogenesis (Weinberger 1996;Raedler et al. 1998). A causal relationship pertaining to disturbed brain ontogenesis and schizophrenia comes from epidemiological studies that have identified several risk factors that, acting during pregnancy, increase the incidence of the disease in offspring. Maternal infection with influenza virus in the second trimester of preg...

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1 Interleukin-1 (IL-1) is an important mediator of immunoin¯ammatory responses in the brain. In the present study, we examined whether prostaglandin E 2 (PGE 2 ) production after IL-1b stimulation is dependent upon activation of protein kinases in astroglial cells. 2 Astrocyte cultures stimulated with IL-1b or the phorbol ester, PMA signi®cantly increased PGE 2 secretion. The stimulatory action of IL-1b on PGE 2 production was totally abolished by NS-398, a speci®c inhibitor of cyclo-oxygenase-2 activity, as well as by the protein synthesis inhibitor cycloheximide, and the glucocorticoid dexamethasone. Furthermore, IL-1b induced the expression of COX-2 mRNA. This occurred early at 2 h, with a maximum at 4 h and declined at 12 h. IL-1 b treatment also induced the expression of COX-2 protein as determined by immunoblot analysis. In that case the expression of the protein remained high at least up to 12 h. 3 Treatment of cells with protein kinase C inhibitors (H-7, bisindolylmaleimide and calphostin C) inhibited IL-1b stimulation of PGE 2 . In addition, PKC-depleted astrocyte cultures by overnight treatment with PMA no longer responded to PMA or IL-1. The ablation of the e ects of PMA and IL-1b on PGE 2 production, likely results from down-regulation of phorbol ester sensitive-PKC isoenzymes. Immunoblot analysis demonstrated the translocation of the conventional isoform cPKC-a from cytosol to membrane following treatment with IL-1b. 4 In addition, IL-1b treatment led to activation of extracellular signal-regulated kinase (ERK1/2) and p38 subgroups of MAP kinases in astroglial cells. Interestingly, the inhibition of ERK kinase with PD 98059, as well as the inhibition of p38 MAPK with SB 203580, prevented IL-1b-induced PGE 2 release. 5 ERK1/2 activation by IL-1b was sensitive to inhibition by the PKC inhibitor bisindolylmaleimide suggesting that ERK phosphorylation is a downstream signal of PKC activation. 6 These results suggest key roles for PKC as well as for ERK1/2 and p38 MAP kinase cascades in the biosynthesis of PGE 2 , likely by regulating the induction of cyclo-oxygenase-2, in IL-1b-stimulated astroglial cells.

Interleukin-1 receptor antagonist (IL-1ra) is an important anti-inflammatory cytokine that blocks all known actions of IL-1 and markedly protects against experimentally induced ischemic, excitotoxic, and traumatic brain insults. Cannabinoids (CBs) also exert potent anti-inflammatory and neuroprotective effects, but the mechanisms of their actions are unknown. Here we tested the hypothesis that the actions of CBs are mediated by endogenous IL-1ra. We report for the first time that both CB1 and CB2 receptors modulate release of endogenous IL-1ra from primary cultured glial cells. Activation of CB1 or CB2 receptors increased lipopolysaccharide-induced IL-1ra release, and specific CB1 or CB2 antagonists blocked lipopolysaccharide-induced production of IL-1ra from glial cells. Comparison of neuronal cultures from wild-type mice and mice lacking IL-1ra (knock-out) indicates that endogenous IL-1ra is essential for the neuro-protective effects of CBs against excessive activation of glutamate receptors (excitotoxicity) in response to S-AMPA or NMDA. Similarly, analysis of mixed glial cultures from IL-1ra knock-out mice indicates that endogenous IL-1ra is required for the CB-induced inhibition of nitric oxide production in response to bacterial lipopolysaccharide. These data suggest a novel neuroprotective mechanism of action for CBs in response to inflammatory or excitotoxic insults that is mediated by both CB1 and CB2 receptor-dependent pathways.

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Neurospheres are clonal cellular aggregates of neural stem/precursor cells that grow in culture as free-floating clusters. Activation of CB1 cannabinoid receptors, which are expressed by these cells, promotes proliferation. In the present study we investigated the expression of CB2 cannabinoid receptors and the effect of exogenous cannabinoids on neural stem/precursor cell proliferation. Neurospheres containing nestin-positive and sn-1 diacylglycerol lipase alpha-positive cells expressed both CB1 and CB2 receptors, which were maintained through several passages. Application of the non-selective cannabinoid agonist (HU-210, 0.5 microM) stimulated bromodeoxyuridine incorporation and neurosphere formation. This action involved both CB1 and CB2 receptors as neurosphere formation was stimulated by either selective CB1 [arachidonyl-2'chloroethylamide/(all Z)-N-(2-cycloethyl)-5,8,11,14-eicosatetraenamide (ACEA), 200 nM and 1 microM] or CB2 (JWH-056, 0.5 microM) agonists. In addition, CB1 or CB2 antagonists (1 microM SR-141716A and SR-144528, respectively) blocked basal proliferation, suggesting that endogenous cannabinoids are implicated in neurosphere proliferation. In addition, cannabinoid agonist-stimulated proliferation was reduced by the Akt translocation inhibitor BML-257 (12.5 microM), suggesting a role for phosphoinositide-3 kinase signalling. Together, our results suggest that cannabinoids stimulate proliferation of neural stem/precursor cells acting on both CB1 and CB2 cannabinoid receptors through a phosphoinositide-3 kinase/Akt pathway.

Proinflammatory mediators have been implicated in demyelinating disorders, including multiple sclerosis, whereas it has been proposed that the anti‐inflammatory cytokines interleukin‐ (IL‐) 4 and IL‐10 participate in disease recovery. The present study analysed the effect of interferon‐γ (IFN‐γ) and bacterial endotoxin (lipopolysaccharide, LPS) on proliferation and survival of progenitors and differentiated oligodendrocytes. We also investigated the presence of receptors for IL‐4 and IL‐10 in oligodendroglial cells and explored a possible protective action of IL‐4 and IL‐10 in cultures following LPS/IFN‐γ. Finally, the role of endogenous nitric oxide (NO) on cell viability and the modulatory action of IL‐4 and IL‐10 on inducible nitric oxide synthase (iNOS) expression were also analysed. We report that LPS and/or IFN‐γ reduced proliferation and viability of oligodendroglial cells. Cell death, presumably by apoptosis as evidence by TUNEL and Annexin V binding, was observed following LPS/IFN‐γ, progenitors being more sensitive than differentiated cells. At both developmental stages, LPS/IFN‐γ‐treated cultures expressed iNOS protein and released micromolar concentrations of NO. In progenitors, LPS/IFN‐γ‐mediated cell damage was partially dependent on endogenous NO production, whereas NO was fundamental for cytotoxicity of differentiated oligodendrocytes. Both cell types expressed mRNA for IL‐4 and IL‐10 receptors and expression of IL‐10 receptors at the protein level was also demonstrated. Treatment with either cytokine inhibited the expression of iNOS resulting from the proinflammatory stimulation. IL‐10 was more effective than IL‐4 in suppressing iNOS expression and, interestingly, IL‐10 conferred protection against oligodendroglial death evoked by LPS/IFN‐γ. Our data raise the question of whether IL‐10 may play a protective role in demyelinating diseases, not only downregulating the function of inflammatory cells but also promoting survival of progenitors and differentiated oligodendrocytes.