Role of cannabinoid CB2 receptor in the reinforcing actions of ethanol

This study examines the role of the cannabinoid CB2 receptor (CB2 r) on the vulnerability to ethanol consumption. The time-related and dose-response effects of ethanol on rectal temperature, handling-induced convulsions (HIC) and blood ethanol concentrations were evaluated in CB2 KO and wild-type (WT) mice. The reinforcing properties of ethanol were evaluated in conditioned place preference (CPP), preference and voluntary ethanol consumption and oral ethanol self-administration. Water-maintained behavior schedule was performed to evaluate the degree of motivation induced by a natural stimulus. Preference for non-alcohol tastants assay was performed to evaluate the differences in taste sensitivity. Tyrosine hydroxylase (TH) and μ-opioid receptor gene expressions were also measured in the ventral tegmental area and nucleus accumbens (NAcc), respectively. CB2 KO mice presented increased HIC score, ethanol-CPP, voluntary ethanol consumption and preference, acquisition of ethanol self-administration, and increased motivation to drink ethanol compared with WT mice. No differences were found between genotypes in the water-maintained behavior schedule or preference for non-alcohol tastants. Naïve CB2 KO mice presented increased μ-opioid receptor gene expression in NAcc. Acute ethanol administration (1-2 g/kg) increased TH and μ-opioid receptor gene expressions in CB2 KO mice, whereas the lower dose of ethanol decreased TH gene expression in WT mice. These results suggest that deletion of the CB2 r gene increased preference for and vulnerability to ethanol consumption, at least in part, by increased ethanol-induced sensitivity of the TH and μ-opioid receptor gene expressions in mesolimbic neurons. Future studies will determine the role of CB2 r as a target for the treatment of problems related with alcohol consumption.This research was supported by ‘Instituto de Salud Carlos III’ (RETICS, RD06/0001/1004, RD12/0028/0019), ‘Plan Nacional Sobre Drogas’ (PNSD 2007/061; 2011/043), Fundación Sociosanitaria de Castilla—La Mancha, (FISCAM) and ‘Ministerio de Economía y Competitividad’ (#SAF 2008-01106, SAF 2011-23420) grants to J.M. Postdoctoral fellows A.O.A and A.T, and Raquel Poveda (R.P., technician) and Mar Ruiz (M.R., technician) are supported by FISCAM. F.N. (postdoctoral fellow), A.A.F. (postdoctoral fellow) and Analía Rico (A.R., technician) are supported by RETICS. MSGG (postdoctoral fellow) and Patricia Rodríguez (P.R., technician) are supported by Miguel Hernández University. We thank R.P., M.R., A.R and P.R. for excellent technical assistance. The partial support of FEDER funds (EU) is also acknowledged.Peer reviewe

Overexpression of CB2 cannabinoid receptors results in neuroprotection against behavioral and neurochemical alterations induced by intracaudate administration of 6-hydroxydopamine

The role of CB2 cannabinoid receptors in the behavioral and neurochemical changes induced by intracaudate administration of 6-hydroxydopamine (6-OHDA) was evaluated. 6-OHDA (12 μg/4 μL) or its vehicle was injected in the caudate-putamen (CPu) of mice overexpressing the CB2 cannabinoid receptor (CB2xP) and wild type (WT) mice. Motor impairment, emotional behavior, and cognitive alterations were evaluated. Tyrosine hydroxylase (TH), glial fibrillary acidic protein (GFAP), and ionized calcium-binding adapter molecule 1 (Iba-1) were measured by immunocytochemistry in the CPu and/or substantia nigra (SN) of CB2xP mice and WT mice. Oxidative/nitrosative and neuroinflammatory parameters were also measured in the CPu and cortex of 6-OHDA-treated and sham-treated mice. 6-OHDA-treated CB2xP mice presented significantly less motor deterioration than 6-OHDA-treated WT mice. Immunocytochemical analysis of tyrosine hydroxylase in the SN and CPu revealed significantly fewer lesions in CB2xP mice than in WT mice. GFAP and Iba-1 immunostaining revealed less astrocyte and microglia recruitment to the treated area of the CPu in CB2xP mice. Malonyldialdehyde (MDA) concentrations were lower in the striatum and cerebral cortex of sham-treated CB2xP mice than in sham-treated WT mice. The administration of 6-OHDA increased MDA levels in both WT mice and CB2xP mice; it increased the oxidized (GSSG)/reduced (GSH) glutathione ratio in the striatum in WT mice alone compared with matched sham-treated controls. The results revealed that overexpression of CB2 cannabinoid receptors decreased the extent of motor impairment and dopaminergic neuronal loss, reduced the recruitment of astrocytes and microglia to the lesion, and decreased the level of various oxidative parameters. These results suggest that CB2 receptors offer neuroprotection against dopaminergic injury. © 2012 Elsevier Inc.This work was also supported by the >Fundacion para la Investigacion Sanitaria en Castilla-La Mancha (FISCAM)> project PI-2008/21 to MFG, >Incorporacion de Grupos Emergentes> FIS-Carlos III and project PI-080693 from ISCII-Carlos III to MFG and MES. AT, JMPO, and AOA are postdoctoral fellows from FISCAM. MSGG and FN are predoctoral fellows from the Spanish Ministry of Health and the Spanish Ministry of Science and Innovation, respectively.Peer Reviewe

Regulatory role of the cannabinoid CB 2

BACKGROUND AND PURPOSE: Stress exposure produces excitotoxicity and neuroinflammation, contributing to the cellular damage observed in stress-related neuropathologies. The endocannabinoids provide a homeostatic system, present in stress-responsive neural circuits. Here, we have assessed the possible regulatory role of cannabinoid CB(2) receptors in stress-induced excitotoxicity and neuroinflammation. EXPERIMENTAL APPROACH: We used wild type (WT), transgenic overexpressing CB(2) receptors (CB2xP) and CB(2) receptor knockout (CB2-KO) mice exposed to immobilization and acoustic stress (2 h·day(−1) for 4 days). The CB(2) receptor agonist JWH-133 was administered daily (2 mg·kg(−1), i.p.) to WT and CB2-KO animals. Glutamate uptake was measured in synaptosomes from frontal cortex; Western blots and RT-PCR were used to measure proinflammatory cytokines, enzymes and mediators in homogenates of frontal cortex. KEY RESULTS: Increased plasma corticosterone induced by stress was not modified by manipulating CB(2) receptors. JWH-133 treatment or overexpression of CB(2) receptors increased control levels of glutamate uptake, which were reduced by stress back to control levels. JWH-133 prevented the stress-induced increase in proinflammatory cytokines (TNF-α and CCL2), in NF-κB, and in NOS-2 and COX-2 and in the consequent cellular oxidative and nitrosative damage (lipid peroxidation). CB2xP mice exhibited anti-inflammatory or neuroprotective actions similar to those in JWH-133 pretreated animals. Conversely, lack of CB(2) receptors (CB2-KO mice) exacerbated stress-induced neuroinflammatory responses and confirmed that effects of JWH-133 were mediated through CB(2) receptors. CONCLUSIONS AND IMPLICATIONS: Pharmacological manipulation of CB(2) receptors is a potential therapeutic strategy for the treatment of stress-related pathologies with a neuroinflammatory component, such as depression

Decreased cocaine motor sensitization and self-administration in mice overexpressing cannabinoid CB 2 receptors

The potential involvement of the cannabinoid CB 2 receptors (CB 2 r) in the adaptive responses induced by cocaine was studied in transgenic mice overexpressing the CB 2 r (CB 2 xP) and in wild-type (WT) littermates. For this purpose, the acute and sensitized locomotor responses to cocaine, conditioned place preference, and cocaine intravenous self-administration were evaluated. In addition, we assessed whether CB 2 r were localized in neurons and/or astrocytes, and whether they colocalized with dopamine D1 and D2 receptors (D1Dr and D2Dr). Dopamine (DA) extracellular levels in the nucleus accumbens (NAcc), and gene expression of tyrosine hydroxylase (TH) and DA transporter (DAT) in the ventral tegmental area (VTA), and-opioid and cannabinoid CB 1 receptors in the NAcc were also studied in both genotypes. CB 2 xP mice showed decreased motor response to acute administration of cocaine (10-20 mg/kg) and cocaine-induced motor sensitization compared with WT mice. CB 2 xP mice presented cocaine-induced conditioned place aversion and self-administered less cocaine than WT mice. CB 2 r were found in neurons and astrocytes and colocalized with D2Dr in the VTA and NAcc. No significant differences in extracellular DA levels in the NAcc were observed between genotypes after cocaine administration. Under baseline conditions, TH and DAT gene expression was higher and-opioid receptor gene expression was lower in CB 2 xP than in WT mice. However, both genotypes showed similar changes in TH and-opioid receptor gene expression after cocaine challenge independently of the pretreatment received. Importantly, the cocaine challenge decreased DAT gene expression to a lesser extent in cocaine-pretreated CB 2 xP than in cocaine-pretreated WT mice. These results revealed that CB 2 r are involved in cocaine motor responses and cocaine self-administration, suggesting that this receptor could represent a promising target to develop novel treatments for cocaine addiction. © 2012 American College of Neuropsychopharmacology.Peer Reviewe