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1. The time dependence of the increase in amplitude (facilitation) of a second end‐plate potential (e.p.p.) elicited within 10–100 msec of a preceding e.p.p. was examined at neuromuscular junctions in sartorius muscles of toads. Facilitation was defined by two characteristics, initial facilitation and the time constant of its exponential decay.

Miniature end plate currents (MEPCs) were recorded with focal extracellular electrodes from white extraocular muscle fibres of a marine teleost fish,Trachurus novaezelandiae, over a temperature range of 5 °C to 27 °C.1.Teleost MEPCs rose rapidly, attaining a maximum amplitude of 250–500 µV, withTGof about 150 µs at 15 °C (Figs. 1, 2).2.Decay of MEPCs was exponential, with t=1 ms at 15 °C (Figs. 3, 5). t was an exponential function of absolute temperature, withEa=70 kJ (Fig. 5).3.t ofTrachurus MEPCs was consistently smaller than values of t reported for other vertebrate end plates (Table 1). Low t is correlated with a high degree of lipid unsaturation in teleosts, and may be caused by increased membrane fluidity.4.Frequency distributions ofTG(Fig. 2) and t (Fig. 4) at a single recording site appear to represent one population of events, skewed toward smaller values.5.Teleost MEPCs also appeared to be normal cholinergic MEPCs in that their rates of decay were decreased by neostigmine, ethanol and membrane hyperpolarization.