Augmented anandamide signalling in the substantia nigra pars reticulata mediates panicolytic-like effects in mice confronted by Crotalus durissus terrificus pit vipers.

RATIONALE: The endocannabinoid modulation of fear and anxiety due to the on-demand synthesis and degradation is supported by a large body of research. Although it has been proposed that anandamide (AEA) in the substantia nigra pars reticulata (SNpr) seems to be important for the organisation of innate fear-related behaviours, a role for endogenous AEA has yet to be clarified. METHODS: Mice were treated with the fatty acid amide hydrolase (FAAH) selective inhibitor URB597 at different concentrations (0.01, 0.1, 1 nmol/0.1 µL) in the SNpr and confronted by rattlesnakes (Crotalus durissus terrificus). The most effective dose of URB597 (1 nmol) was also preceded by microinjections of the CB1 receptor antagonist AM251 (0.1 nmol) into the SNpr, and mice were then confronted by the venomous snake. RESULTS: URB597 (0.1 and 1 nmol) in the SNpr decreased the expression of defensive behaviours such as defensive attention, escape, and time spent inside the burrow of mice confronted by rattlesnakes. Moreover, pretreatment of SNpr with AM251 suppressed these antiaversive effects of URB597 in this midbrain structure. CONCLUSION: Overall, these data clearly indicate that the panicolytic consequences of endogenous AEA enhancement in the SNpr are mediated by CB1 receptor signalling.

URB597 Prevents the Short-Term Excitotoxic Cell Damage in Rat Cortical Slices: Role of Cannabinoid 1 Receptors.

Endocannabinoid-based therapies constitute an emerging tool for the potential treatment of neurodegenerative disorders, requiring characterization at the experimental level. The effects of URB597, an inhibitor of the fatty acid amide hydrolase (FAAH), were tested against the quinolinic acid (QUIN)-induced early toxic effects in rat cortical slices, and compared with those effects exerted by the endocannabinoid anandamide (AEA). URB597 prevented the QUIN-induced loss of mitochondrial function/cell viability and lipid peroxidation, while reduced necrosis, and to a lesser extent, apoptosis. The protective effects of URB597 were mediated by activation of cannabinoid receptor 1 (CB1r), as evidenced by their inhibition by the selective CB1r antagonist AM281. Similar effects were observed when testing AEA against QUIN toxicity. Our findings demonstrate the neuroprotective properties of URB597 during the early stages of excitotoxic damage to cortical tissue, suggesting that these properties are mediated by FAAH inhibition, and might be linked to the protective effects of AEA, or the combination of endocannabinoids.

URB597 ameliorates the deleterious effects induced by binge alcohol consumption in adolescent rats.

Heavy episodic drinking or binge drinking during adolescence may elicit serious neurotoxic consequences in cerebral areas (e.g., the prefrontal cortex, i.e., PFC) and the hippocampus, delay the maturation of the brain and increase the probability of drug abuse and dependence. The endocannabinoid system plays an important role in neuroprotection by reducing oxidative stress and neuroinflammation. In the present study, we aimed to investigate whether URB597, an inhibitor of the metabolic enzyme of the endocannabinoid anandamide (AEA), altered the effects of acute and chronic alcohol administration beginning during rat adolescence on recognition memory, neuroinflammation and brain-derived neurotrophic factor (BDNF) levels. The animals received intraperitoneal injections of URB597 (0.3 mg/Kg) or vehicle followed by the oral administration of ethanol (3 or 6 g/Kg) or distilled water for 3 consecutive days in one week (acute binging) or over 4 weeks (chronic binging). The groups were submitted to the novel object recognition task, and their PFCs and hippocampi were removed for analyses of the cytokine and BDNF levels. URB597 potentiated long-term memory after the 3 mg/Kg acute alcohol administration. The chronic binge alcohol administration increased the interferon (IFN)-γ and tumor necrosis factor (TNF)-α levels in the PFC and hippocampus and the interleukin (IL)-10 and BDNF levels in the PFC, and these effects were prevented by URB597. Our results indicate that the neuromodulation facilitated by AEA can reduce the neuroimmune response induced by the chronic administration of alcohol beginning in adolescence in rats.

URB597 reduces biochemical, behavioral and morphological alterations in two neurotoxic models in rats.

BACKGROUND: URB597 is a compound largely linked to the inhibition of fatty acid amide hydrolase (FAAH), an enzyme responsible for the metabolic degradation of the endocannabinoid anandamide (AEA). Despite this pharmacological property accounts for its modulatory profile demonstrated in some neurotoxic paradigms, the possible protective properties of this agent have been poorly investigated, and deserve exploration in different neurotoxic models. In this study, we explored the effects of URB597 on oxidative damage to lipids and other major endpoints of toxicity in two neurotoxic models in vivo in rats (the first one produced by the mitochondrial neurotoxin 3-nitropropionic acid [3-NP], and the other generated by the striatal injection of the pro-oxidant toxin 6-hydroxidopamine [6-OHDA]) in order to provide further supporting evidence of its modulatory profile. METHODS: Male Wistar adult rats were treated for 5 or 7 consecutive days with URB597 (0.3mg/kg, i.p.) and simultaneously exposed to three injections of 3-NP (30mg/kg, i.p.) or a single intrastriatal infusion of 6-OHDA (0.02mg/2µl), respectively. Twenty four hours after all treatments were administered, lipid peroxidation was measured in the striatum of 3-NP-treated rats, and in the midbrain of 6-OHDA-treated rats. Motor skills and histological assessment in the striatum were also evaluated in 3-NP-treated rats 6 and 7days after the last drug administration, respectively; whereas apomorphine-induced circling behavior and tyrosine hydroxylase immunolocalization in the striatum and substantia nigra were investigated 21 and 22days after the last drug infusion, respectively. RESULTS: URB597 prevented the oxidative damage to lipids induced by 3-NP in the striatum, and this effect could account for the attenuation of motor deficits in this model. Attenuation of motor disturbances induced by URB597 in both models was associated with the morphological preservation of the striatum in the 3-NP model and the partial preservation of tyrosine hydroxylase in the 6-OHDA model in the SNpc and striatum. CONCLUSION: The modulatory actions exerted by URB597 in both toxic models support its potential against toxic conditions implying motor and neurochemical alterations linked to energy depletion, excitotoxicity and oxidative stress. Although most of these effects could be attributable to its action on FAAH and further AEA accumulation, in light of our present findings other properties are suggested.

URB597 inhibits oxidative stress induced by alcohol binging in the prefrontal cortex of adolescent rats.

Heavy episodic drinking (binging), which is highly prevalent among teenagers, results in oxidative damage. Because the prefrontal cortex (PFC) is not completely mature in adolescents, this brain region may be more vulnerable to the effects of alcohol during adolescence. As endocannabinoids may protect the immature PFC from the harmful effects of high doses of alcohol, this study investigated the effect of the fatty acid amide hydrolase (FAAH) inhibitor URB597 on oxidative stress induced by acute or chronic binge alcohol intake in adolescent rats. At 40min after intraperitoneal pre-treatment with URB597 (0.3mg/kg) or vehicle (Veh), ethanol (EtOH; 3 or 6g/kg, intragastrically) or distilled water (DW) was administered in 3 consecutive sessions (acute binging) or 3 consecutive sessions over 4 weeks (chronic binging). Oxidative stress in PFC slices in situ was measured by dihydroethidium fluorescence staining. At the higher EtOH dose (6g/kg), pre-treatment with URB597 significantly reduced (p<0.01) the production of superoxide anions in the PFC after acute (42.8% decrease) and chronic binge EtOH consumption (44.9% decrease) compared with pre-treatment with Veh. As URB597 decreases anandamide metabolism, this evidence shows an antioxidant effect of endocannabinoids to suppress acute and chronic binge alcohol intake-induced oxidative stress in the PFC of adolescent rats.