Wavelength dependence of the optically recorded action potentials in guinea pig atrial muscles

The optically recorded action potentials of the frog atrial muscles which l ack transverse tubules showed different features from those reported by Hei ny and Vergara (Heiny JA, Vergara J. Optical signals from surface and T sys tem membranes in skeletal muscle fibers. J Gen Physiol 1982;80:203-230) in skeletal muscles (Fujishiro N, Kawata H. The wavelength dependence of optic ally recorded action potentials in the atrial muscles of the bullfrog (Rana catesbeiana). Comp Biochem Physiol 1996;114A:153-157). We examined whether or not the differences were consistent in other atrial muscles which lack transverse tubules with guinea pig atrial muscles. Two dyes (merocyanine rh odanine and merocyanine oxazolone) were used, and the dependence of the max imum rising phase of the optical signals on the wavelength of the incident beam was analyzed. No dependence was observed between them, and this findin g was consistent with the structure of the membrane system of the guinea pi g atrial muscles. The optical signals recorded at 718 nm of the incident be am from the guinea pig atrial muscles which stained with merocyanine oxazol one showed a more prominent second rising phase after the initial rapid ris ing phase of the optical signal than that recorded in the frog atrial muscl es. This phase was not observed in the optical signals recorded at other wa velengths. The features of the optically recorded action potentials in guin ea pig atrial muscles were consistent with those recorded in frog atrial mu scles. Nifedipine did not affect the second rising phase. (C) 1999 Elsevier Science Inc. All rights reserved.