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The three-dimensional (3D) diffusion model of Fogelson, A. L., and R. S. Zucker (1985. Biophys. J. 48: 1003-1017) has been employed as the basis of a refined version of the "Ca theory" for neurotransmitter release. As such, it has been studied here as to its ability to predict the time course of release under various conditions. In particular, conditions(More)
Release and facilitated release of transmitter at neuromuscular junctions of the crayfish Astacus were measured as a function of [Ca]0 at single junctions using a patch clamp technique. Tests were made of a quantitative model that relates release of transmitter to [Ca]i. The model assumes three processes, entry of Ca during the action potential, release of(More)
1. Presynaptic effects of muscarine on neurotransmitter release were studied at the frog neuromuscular junction, using focal depolarization of the presynaptic terminal to different levels. 2. Muscarine (10 microM) had a dual effect on ACh release: concomitant inhibition and enhancement of release at the same patch of presynaptic membrane. 3. These two(More)
Quantal synaptic currents were recorded at nerve terminations on the opener muscle of crayfish using a macro-patch-clamp electrode, and the release was elicited by depolarizing current pulses applied to the terminal through the same electrode. After 2 ms depolarization pulses at low temperature, release started with about 2 ms delay after the onset of(More)
In excitatory neuromuscular junctions of crayfish quantal synaptic currents were recorded focally by means of a macro-patch-clamp electrode. Through the same electrode the nerve terminal was depolarized by current pulses which elicited quantal postsynaptic currents (pEPSCs). The terminals were electrically inexcitable and the quantum content (m) of pEPSCs(More)
1. Propagation of action potentials at high frequency was studied in a branching axon of the lobster by means of simultaneous intracellular recording both before and after the branch point. 2. Although the branching axon studied has a geometrical ratio close to one (perfect impedance matching) conduction across the branch point failed at stimulation(More)
1. A technique has been developed to monitor neurotransmitter release simultaneously with intracellular Ca2+ concentration ([Ca2+]i) in single release boutons whose diameters range from 3 to 5 microns. 2. Using this technique, we have found a highly non-linear relationship between the rate of asynchronous release and [Ca2+]i. The Hill coefficient lies(More)
1. The ionic mechanisms involved in block of conduction of action potentials following high frequency stimulation were studied in a branching axon of the lobster Panulirus penicillatus. 2. A 2-3 mM increase in extracellular K concentration (normal concentration 12 mM) produced block of conduction into both daughter branches. 3. While conduction block(More)
1. Spike propagation across the nonhomogeneous section of the giant axon in ganglion T3 of the cockroach was analyzed by intracellular microelectrodes recording at the posterior and anterior ends of T3. Ascending and descending potentials were evoked by stimulation of A5-A6 and T2-T3 connectives. 2. At high frequencies, descending and ascending impulses(More)
The physiological responses, receptive fields and morphology of individual nociceptor (N) neurones have been studied in the leech. In each of the midbody ganglia there are four N cells (two on either side). Each N cell has a distinctive territory that it supplies in the periphery, on the surface or internally. 1. Both N cells respond selectively to noxious(More)