Experimental Parkinsonism Alters Endocannabinoid Degradation: Implications for Striatal Glutamatergic Transmission

Open Access
Publisher Website
Google Scholar
Abstract
Cannabinoid receptors and their endogenous ligands have been recently identified in the brain as potent inhibitors of neurotransmitter release. Here we show that, in a rat model of Parkinson9s disease induced by unilateral nigral lesion with 6-hydroxydopamine (6-OHDA), the striatal levels of anandamide, but not that of the other endocannabinoid 2-arachidonoylglycerol, were increased. Moreover, we observed a decreased activity of the anandamide membrane transporter (AMT) and of the anandamide hydrolase [fatty acid amide hydrolase (FAAH)], whereas the binding of anandamide to cannabinoid receptors was unaffected. Spontaneous glutamatergic activity recorded from striatal spiny neurons was higher in 6-OHDA-lesioned rats. Inhibition of AMT byN-(4-hydroxyphenyl)-arachidonoylamide (AM-404) or by VDM11, or stimulation of the cannabinoid CB1 receptor by HU-210 reduced glutamatergic spontaneous activity in both naı̈ve and 6-OHDA-lesioned animals to a similar extent. Conversely, the FAAH inhibitors phenylmethylsulfonyl fluoride and methyl-arachidonoyl fluorophosphonate were much more effective in 6-OHDA-lesioned animals. The present study shows that inhibition of anandamide hydrolysis might represent a possible target to decrease the abnormal cortical glutamatergic drive in Parkinson9s disease.