This study was undertaken to characterize further the central cannabinoid receptors in rat primary neuronal cell cultures from selected brain structures. By using [ 3H]SR141716A, the specific OB1 receptor antagonist, we demonstrate in cortical neurons the presence of a high density of specific binding sites (Brnax = 139 ± 9 fmol/mg of protein) displaying a high affinity (KD = 0.76 ± 0.09 nM). The two cannabinoid receptor agonists, OP 55940 and WIN 55212-2, inhibited in a concentrationdependent manner cyclic AMP production induced by either 1~M forskolin or isoproterenol with EC 50 values in the nanomolar range (4.6 and 65 nM with forskolin and 1.0 and 5.1 nM with isoproterenol for CP 55940 and WIN 55212-2, respectively). Moreover, in striatal neurons and cerebellar granule cells, OP 55940 was also able to reduce the cyclic AMP accumulation induced by 1 ,uM forskolin with a potency similar to that observed in cortical neurons (E050 values of 3.5 and 1.9 nM in striatum and cerebellum, respectively). SR 141716A antagonized the OP 55940-and WIN 55212-2-induced inhibition of cyclic AMP accumulation, suggesting CB1 receptor-specific mediation of these effects on all primary cultures tested. Furthermore, OP 55940 was unable to induce mitogenactivated protein kinase activation in either cortical or striatal neurons. In conclusion, our results show nanomolar efficiencies for OP 55940 and WIN 5521 2-2 on adenylyl cyclase activity and no effect on any other signal transduction pathway investigated in primary neuronal cultures.

A protein associated with the peripheral-type benzodiazepine receptor (PRAX-1) has recently been cloned, but its regional distribution in the central nervous system and its function remain to be clarified. In situ hybridization was carried out to localize PRAX-1 mRNA in the rat brain and revealed a high expression of the transcript in limbic structures such as the CA1 region of the hippocampus, as well as the dentate gyrus, septum, amygdala, and the islands of Calleja. A dense hybridization signal was also observed in the nucleus accumbens, caudate nucleus, olfactory tubercle, pineal gland, and cerebellar cortex. PRAX-1 mRNA expression was largely neuronal; it colocalized with neuron-specific enolase but not glial fibrillary acidic protein.Long-term treatments (21 days) with the neuroleptic haloperidol increased PRAX-1 mRNA expression only in the dentate gyrus, whereas anxiolytic/anticonvulsant diazepam had no effect in any of the hippocampal region studied. Repeated electroconvulsive shock administration significantly enhanced PRAX1 expression in the CA1 subfield and dentate gyrus. Several classes of antidepressant treatment, including serotonin selective reuptake inhibitor (fluoxetine), mixed serotonin-and norepinephrine-uptake inhibitor (imipramine), and monoamine oxidase inhibitors (iproniazid and tranylcypromine), shared this effect. Furthermore, the selec-, which shows an antidepressant profile in animal studies, also enhanced PRAX-1 mRNA expression. These results point to a potential role of PRAX-1 function in the central nervous system and suggest that the up-regulation of PRAX-1 mRNA represents a common action of chronic antidepressant treatment.PRAX-1 has recently been isolated by the yeast two-hybrid system, using the peripheral-type benzodiazepine receptor (PBR) as bait (Galiegue et al., 1999). This 1857-amino acid protein is a single 220-to 250-kDa entity and is encoded by a 7.5-kilobase mRNA that is highly expressed in the central nervous system and at lower levels in some peripheral tissues. PRAX-1 was shown to interact with PBR in several cell lines, but this interaction has not yet been demonstrated in the central nervous system (CNS). Subcellular localization studies of PBR have shown that it is linked to mitochondria in the rat brain (Basile and Skolnick, 1986), as well as in the rat adrenal gland (Anholt et al., 1986) and many peripheral organs (Antkiewicz-Michaluk et al., 1988). More recently, the use of confocal microscopy further confirmed the abundant mitochondrial localization of PBR (Garnier et al., 1993). PRAX-1 protein was shown to be present in both mitochondrial and cytoplasmic compartments (Galiegue et al., 1999). A comparison of PRAX-1 and PBR expression profiles revealed that some tissues, like lung or testis, express PBR but are devoid of detectable PRAX-1 expression (Burgi et al., 1999). Furthermore, immunohistochemical analysis proved this protein to be highly expressed in the hippocampus, which demonstrates a very low level of PBR expression (Anholt et al., 1985). The...

Obesity epidemic continues to spread and obesity rates are increasing in the world. In addition to public health effort to reduce obesity, there is a need to better understand the underlying biology to enable more effective treatment and the discovery of new pharmacological agents. Abhydrolase domain-containing protein 11 (ABHD11) is a serine hydrolase enzyme, localized in mitochondria, that can synthesize the endocannabinoid 2-arachidonoyl glycerol (2AG) in vitro. In vivo preclinical studies demonstrated that knockout ABHD11 mice have a similar 2AG level as WT mice and exhibit a lean metabolic phenotype. Such mice resist to weight gain in Diet Induced Obesity studies (DIO) and display normal biochemical plasma parameters. Metabolic and transcriptomic analyses on serum and tissues of ABHD11 KO mice from DIO studies show a modulation in bile salts associated with reduced fat intestinal absorption. These data suggest that modulating ABHD11 signaling pathway could be of therapeutic value for the treatment of metabolic disorders.