Identification and spatio-temporal analysis of the rat pelvic pacemaker region using a macro zoom microscope and voltage-sensitive dye

Abstract

As we reported in the last meeting in Sendai, we established in situ Ca²⁺ imaging technique of the rat renal pelvis using a macro zoom microscope (Olympus MVX 10). The clear view and smooth zooming operation with this technique enabled us to search upstream of Ca²⁺ transient and to identify the pacemaker region easily. With higher magnification of the region, we could observe that not only one cell but several cells increased their intracellular Ca²⁺ concentration simultaneously. Interestingly their propagating pathway were slightly different every time. Spontaneous Ca²⁺ rises in the other part of renal pelvis rarely occurred; they never propagated to the downstream. Contrary many spontaneous but asynchronous Ca²⁺ rises were observed in the presence of low concentration of heptanol, a gap junction blocker. Using the same technique we could also successfully record image of di-4-ANEPPS, a voltage-sensitive dye. The initial depolarization occurred at the exactly same place as the Ca²⁺ rise. These results might suggest that the smooth muscle cells connected via gap junctions and with synchronous Ca²⁺ rise played an important role in the pacemaker mechanisms. [J Physiol Sci. 2006;56 Suppl:S148]