Figure 1.

CB₁ receptors are located mainly extrasynaptically but also at the presynaptic active zone and at the postsynaptic density of rat striatal nerve terminals. A, Western blot (representative of 4 similar blots from different groups of animals) comparing CB₁ receptor immunoreactivity, corresponding to the 53 kDa band, in a fraction enriched in the presynaptic active zone (pre), in the postsynaptic density (post), in the nerve terminals portion outside the active zone (extra), and in the initial synaptosomal fraction (whole), from which fractionation was performed. These fractions were obtained by pH fractionation, after solubilization of purified striatal nerve terminals as described in Materials and Methods. Thirty micrograms of protein of each fraction were applied into the SDS-PAGE gel, and a CB₁ antibody was used at a 1:5000 dilution. B, Average distribution of CB₁ receptor immunoreactivity in subsynaptic compartments. The CB₁ receptor density was higher in the extrasynaptic fraction but was also present, to a lesser extent, in the presynaptic active zone and in the postsynaptic density.