Figure 3.

Effect of the Mid peptide on synaptic transmission. The Mid peptide was introduced into presynaptic neurons, while postsynaptic responses were evoked by presynaptic action potentials elicited at 0.05 Hz at 5.1 mM Ca²⁺. (A) EPSPs induced by single action potential before and after the injection of the Mid peptide from a pipette containing 2.5 mM peptide. Postsynaptic potentials recorded at the indicated times were taken from one representative experiment. (a) Ten minutes before the injection, (b) 50 min after the injection, (c) 80 min after the injection. (B) Inhibition of synaptic transmission by the Mid peptide. Normalized average postsynaptic potentials are plotted from experiments with the injection of the Mid peptide (Mid, n = 7), the mutated Mid peptide (m-Mid, n = 6), and the scrambled Mid peptide (s-Mid, n = 6) at 2.5 mM in the pipette. Peak values of the EPSP amplitude were measured and averaged. The resultant values were smoothed by eight-point moving average algorithm and plotted against recording time with t = 0 indicating the beginning of the presynaptic injection. (○), Mid; (◊), m-Mid; (■), s-Mid.