tokens: In the present study , we examined the effects of three SSRIs ( fluvoxamine , sertraline , paroxetine ) , as well as the effects of a sigma - 1 receptor agonist ( 4 - phenyl - 1 - ( 4 - phenylbutyl ) piperidine ( PPBP ) , dehydroepiandrostero - sulphate ( DHEA ) - sulfate ) [ 9 ] , [ 22 ] - [ 28 ] and the selective sigma - 1 receptor agonist SA4503 [ 29 ] , [ 30 ] , on NGF - induced neurite outgrowth in PC12 cells .