tokens: The selective and potent sigma - 1 receptor agonist SA4503 ( 0 . 01 , 0 . 1 , or 1 . 0 micro M ) significantly increased the number of cells with neurite outgrowth by NGF ( 2 . 5 ng / ml ) in PC12 cells , in a concentration - dependent manner ( Figure 3 and 4 ) .