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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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.

Theiler's virus infection of the central nervous system (CNS) induces an immune-mediated demyelinating disease in susceptible mouse strains and serves as a relevant infection model for human multiple sclerosis (MS). Cannabinoids have been shown to exert beneficial effects on animal models of MS and evidence suggests that the endocannabinoid system plays a role in the tonic control of spasticity. In this study we, two selective inhibitors of the putative endocannabinoid transporter and hence of endocannabinoid inactivation, provide an effective therapy for Theiler murine encephalomyelitis virus-induced demyelinating disease (TMEV-IDD). Treatment of TMEV-infected mice with OMDM1 and OMDM2 enhanced anandamide levels in the spinal cord and ameliorated motor symptoms. This was associated with a down-regulation of inflammatory responses in the spinal cord. In addition we show that OMDM1 and OMDM2 down-regulate macrophage function by (i) decreasing the surface expression of major histocompatibility complex (MHC) class II molecules, (ii) inhibiting nitric oxide synthase-2 (NOS-2) expression and (iii) reducing the production of the pro-inflammatory cytokines interleukin-1beta (IL-1b) and interleukin-12 (IL-12p40). Taken together, these results point to the manipulation of the endocannabinoid system as a possible strategy to develop future MS therapeutic drugs.

Theiler's murine encephalomyelitis virus-induced demyelinating disease (TMEV-IDD) is a well-characterized murine model of human multiple sclerosis (MS) that closely resembles the chronic and progressive clinical form of the disease. Recent studies have described the involvement of the cannabinoid system in the progression of the disease and the benefits associated with the administration of cannabinoid agonists. With the objective to study whether "indirect" agonists, that is, compounds able to reinforce the physiological endocannabinoid transmission and, therefore, devoid of the psychotropic effects of "direct" agonists, could be suitable agents for the amelioration of MS neurological deficits, we administered the potent and selective anandamide uptake inhibitor UCM707 to TMEV-infected mice. Our results indicate that treatment during established disease significantly improves the motor function of the diseased mice. At the histological level, UCM707 is able to reduce microglial activation, diminish major histocompatibility complex class II antigen expression, and decrease cellular infiltrates in the spinal cord. Additionally, in microglial cells, UCM707 decreases the production of the proinflammatory cytokines tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and IL-6; reduces nitric oxide levels and inducible nitric oxide synthase expression; and is able to potentiate the action of a subeffective dose of the endocannabinoid anandamide. Overall, these results suggest that agents able to activate the endocannabinoid system could constitute a new series of drugs for the treatment of MS.