Abstract
Time series analysis of evoked transmitter release was performed at the frog [Rana ridibunda] neuromuscular synapse. Clumping of end-plate potentials with similar amplitude was found in the time domain. At low quantal contents periodic oscillations were observed with a period of 14 s. Clumping and oscillations are phenomena of presynaptic origin. The hypothesis that periodic fluctuations occur in Ca concentration inside the presynaptic nerve terminal is concluded.