Fig 5. Prolonged exposure to the cannabimimetic WIN55,212-2 results in down-regulation of the CB1 receptor in control and epileptic cultures.
Immunocytochemical staining for the CB1 receptor in sham control and epileptic (SREDs) hippocampal neuronal cultures following 24 h exposure to potent the cannabimimetic WIN55,212-2 (1000 nM; +WIN) or its inactive enantiomer WIN55,212-3 (1000 nM; −WIN). In cultures exposed to the inactive isomer –WIN (upper panels), CB1 receptor staining (FITC-green) was present throughout a neuronal network of processes (arrowheads) with no discernable differences between control and epileptic. Prolonged exposure to the potent cannabimimetic +WIN (lower panels) resulted in a pronounced down-regulation of the CB1 receptor (arrowheads) equally in both control and epileptic hippocampal cultures. Nuclear staining of DNA with DAPI (blue) revealed that neither the low-Mg2+ treatment or prolonged +WIN exposure had any effect on neuronal culture density (scale = 50 microns).