Brain slices from 7-d-old Wistar rats were exposed to oxygen-glucose deprivation (OGD) for 30 min. OGD slices were incubated with vehicle or with the CB1/CB2 cannabinoid agonist WIN55212 (50 M), the CB1 agonist arachidonyl-2-chloroethylamide (ACEA) (50 M), or the CB2 agonist JW133 (50 M), alone or combined with the CB1 and CB2 receptor antagonist SR 141716 (50 M) or SR 144528 (50 M), respectively. Neuronal damage was assessed by histologic analysis and spectrophotometric determination of lactate dehydrogenase (LDH) efflux into the incubation medium. Additionally, medium glutamate levels were determined by highperformance liquid chromatography (HPLC) and those of tumor necrosis factor ␣ (TNF-␣) by enzyme-linked immunosorbent assay. Finally, inducible nitric oxide synthase (iNOS) and CB1/CB2 receptor expression were determined in slices homogenate by Western blot. Both CB1 and CB2 receptors were expressed in slices. OGD increased CB1 expression, cellular damage, LDH efflux, glutamate and TNF-␣ release, and inducible nitric oxide synthase (iNOS) expression; WIN55212 inhibited all these actions. SR141716 and SR144528 inhibited the effect of R(ϩ)-WIN-55212-2 (WIN), as well as the reduction of LDH efflux by ACEA and JW133, respectively. In conclusion, WIN55212 afforded robust neuroprotection in the forebrain slices exposed to OGD, by acting on glutamatergic excitotoxicity, TNF-␣ release, and iNOS expression; this neuroprotective effect seemed to be mediated by CB1 and CB2 receptors. P erinatal hypoxia-ischemia remains the single most important cause of brain injury in the newborn, leading to death or lifelong sequelae (1,2). The complexities of neonatal hypoxic-ischemic encephalopathy (NHIE) pathophysiology suggest that successful neuroprotection could be achieved only with a multitherapeutic approach (2). In recent years, interest in the neuroprotective possibilities of cannabinoids has grown (3-5). Endocannabinoids emerge as natural brain protective substances in different damaging situations (3,4); in newborn rats, enhanced levels of cannabinoids have been observed in the brain after acute excitotoxic insult (6). Exogenous cannabinoid agonists are neuroprotective in different paradigms of brain injury (7,8); they inhibit intracellular calcium influx, reduce glutamate and TNF-␣ release, decrease stimulated iNOS expression, induce hypothermia, and exert immunomodulatory and antioxidant actions (3-5,9,10). Some of these effects are dependent on the activation of the principal brain cannabinoid receptors, the CB1 receptors, and others are dependent on the molecular properties of the cannabinoid or the activation of non-CB1 receptors (3). There are few studies regarding the possible neuroprotective effect of cannabinoids in newborns. Early studies describe that the administration of anandamide (11) or the cannabinoid agonist ⌬ (9)-tetrahydrocannabinol (12) affords neuroprotection in a newborn rat model with excitotoxic neuronal injury. It has also been demonstrated that the cannabinoid agonist WIN, prevents ea...