inclusion of the gtp analogue guanosine 5'-o-3-thiotriphosphate ( gtp-gamma-s , 500 microm ) or guanylylimidodiphosphate ( gmp-pnp , 500 microm ) or gtp itself ( 1 mm ) in the patch pipette solution resulted in a smaller , slowly activating ca2+ channel current which did not inactivate during a 100 ms voltage step .
C0018366
gmp-pnp
C0018353
gtp