Figure 1.

Electrophysiological Findings following presynaptic h-tau42 injection. (A) Pre- and post-synaptic potential following a direct electrical stimulation of the presynaptic axon. Synaptic transmission fails in 30 min following h-tau42 preinjection (six subsequent stimuli at 5-min intervals). (B) Similar experiment as in (A) (24 subsequent stimulus are shown at 5-min interval) following h-tau42 injection in a T-817MA-treated squid. Transmission block does not occur within the 2-h period. (C) Repetitive stimulation at 100 Hz following h-tau42 injection results in a step like decrease in post-synaptic response amplitude that slowly progresses (post 1,2,3) but shows small variation in amplitude during a given stimulus train. (D) Similar train stimulus paradigm produced reduction of transmitter release, which recuperated to the 80% amplitude in 15 min (post 1, 2, and 3). (E) Power spectra of spontaneous post-synaptic noise. Noise recording at the post-synaptic terminal (upper and lower panels on the left) were taken at 1-min intervals following h-tau42preinjection. Spontaneous release as determined by synaptic noise power spectrum (right panel) in (E), showed rapid reduction within a 12-min interval (reading taken at a 1/minrate). (F) h-tau42 preinjection produces block of presynatic release (c) without affecting presynaptic inward calcium current (b). Preterminal voltage step were repeated every minutes. For further detail see text and Figure 2.