AM 404 leads to neuroprotection against ischemia-induced neuronal injury

Anandamide and 2-AG, the most endocannabinoids studied, are produced “on demand” after cerebral ischemia from membrane associated precursors (Baker et al., 2003). As soon as anandamide is released, the diffusion process is accelerated by a rapid and selective carrier system (Piomelli 2003). The development of a series of anandamide transport inhibitors, to slow its elimination and to magnify its beneficial effects, such as AM404, can provide a new tool to investigate the role of endocannabinoids (Piomelli, 2003). Since it is well known the protective role of anandamide in processes occurring during cerebral ischemia (van der Stelt et al., 2001; Berger et al, 2004), the aim of the present work was to investigate the effect of AM404 against neuronal injury in vivo. The animal model we used was the transient global cerebral ischemia induced by Bilateral Carotid Arteries Occlusion (BCAO) in mongolian gerbils. The compound was given i.p. 5 min after BCAO in a range of doses between 0.01 and 1 mg/kg. To quantify the ischemic damage we measured from 1 hour to 7 days after recirculation, electroencephalographic (EEG) mean total spectral power, spontaneous motor activity, cognitive function, rectal temperature and hippocampal neuronal count, all parameters known to be hardly influenced by BCAO (Peruche et al., 1995). AM404 antagonized hyperlocomotion, evaluated in an “activity cage” on Day 1 and the EEG flattening, on Day 7. AM 404 also induced a significant decrease of rectal temperature, within the first hour, and reversed ischemia-induced cognitive deficit, evaluated through the passive avoidance test, on Day 3. Finally, histological examination, carried out on Day 7 with cresyl violet staining, showed that AM404 protected against neuronal loss in CA1 hippocampal subfield. These results, taken together, demonstrate the anti-ischemic effect of AM 404 suggesting a protective role of endocannabinoids in events occurring during cerebral injury. Since it’s well documented an affinity for vanilloid receptors, experiments are in progress to clarify the mechanism by which AM404 shows its protective effect.