Quantal secretion at frog cutaneous pectoris neuromuscular junctions will be stimulated by various agents, and the amplitude and rate of occurrence of miniature endplate potentials (mepps) will be measured with a modified procedure of fluctuation analysis. This procedure uses the power spectrum of the fluctuations in membrane potential at the endplate together with the second (variance), third (skew) and fourth semi-variants of the fluctuations to compute the mepp parameters. Its results are insensitive to drifting membrane potential, nonlinear summation of mepps and nonstationary rates of occurrence, and they allow changes in the mepp amplitude distribution to be monitored and corrected for. This procedure will also be used to measure the amplitude and rate of occurrence of miniature endplate currents (mepcs) at voltage-clamped lizard or mouse neuromuscular junctions. The ultrastructure of the nerve terminals and their uptake of horseradish peroxidase will be examined in the electron microscope. The junctions will be stimulated by black widow spider venom, La3+, K+-rich solutions, or hypertonic solutions, and the effects of low temperature (1-2 degrees C) and inhibitors of acetylcholine synthesis (hemicholinium-3 or Na+-free, Li+ substituted solutions on the quantal secretion induced by these agents will be tested. The morphologic and electrophysiologic results will be used to characterize the recycling processes which sustain the population of synaptic vesicles and maintain the quantal stores of acetylcholine in the nerve terminals. These recycling processes support the long term function of a synapse, and their malfunction will impair transmission and produce diseased states in an organism.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
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Physiology Study Section (PHY)
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Rockefeller University
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New York
United States
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Hurlbut, W P; Iezzi, N; Fesce, R et al. (1990) Correlation between quantal secretion and vesicle loss at the frog neuromuscular junction. J Physiol 425:501-26
Hurlbut, W P (1989) The correlation between vesicle loss and quantal secretion at the frog neuromuscular junction. Cell Biol Int Rep 13:1053-62
Dekhuijzen, A J; Iezzi, N; Hurlbut, W P (1989) A re-examination of the effects of lanthanum on the frog neuromuscular junction. Pflugers Arch 414:683-9
Ceccarelli, B; Hurlbut, W P; Iezzi, N (1988) Effect of alpha-latrotoxin on the frog neuromuscular junction at low temperature. J Physiol 402:195-217
Fesce, R; Segal, J R; Ceccarelli, B et al. (1986) Effects of black widow spider venom and Ca2+ on quantal secretion at the frog neuromuscular junction. J Gen Physiol 88:59-81
Fesce, R; Segal, J R; Hurlbut, W P (1986) Fluctuation analysis of nonideal shot noise. Application to the neuromuscular junction. J Gen Physiol 88:25-57
Segal, J R; Ceccarelli, B; Fesce, R et al. (1985) Miniature endplate potential frequency and amplitude determined by an extension of Campbell's theorem. Biophys J 47:183-202
Haimann, C; Torri-Tarelli, F; Fesce, R et al. (1985) Measurement of quantal secretion induced by ouabain and its correlation with depletion of synaptic vesicles. J Cell Biol 101:1953-65