Comparison of two procedures of loading with voltage-sensitive dye di-4 ANEPPS in rabbit isolated heart

Recording of monophasic action potentials (MAPs) by optical method using voltage sensitive dyes has been established as possibility to measure membrane potential changes in certain models. We studied two procedures of isolated rabbit hearts loading with di-4-ANEPPS - ldquoslowrdquo method (perfusion with low concentration of dye for longer time) or ldquofastrdquo method (single microinjection of highly concentrated bolus of the dye in the aorta). Signal-to-noise ratio was evaluated in each minute of continuous exposure to excitatory light and persistence of dye in the tissue was estimated. We conclude that both methods enable us to record MAPs, but during long exposure to light the persistence of the dye in the tissue is insufficient in ldquofastrdquo method. Although the ldquoslowrdquo loading affects electrophysiological properties of the heart, in case of rabbit heart it is negligible since its relative resistance to the side-effects of di-4-ANEPPS.