Quantal Analysis of Presynaptic Inhibition, Low (Ca2+)O, and High PressureInteractions at Crustacean Excitatory Synapses

摘要

The cellular mechanisms underlying the effects of high pressure, GABAergicpresynaptic inhibition, and low Ca2+0 on glutamatergic excitatory synaptic transmission were studied in the opener muscle of the lobster walking leg. Excitatory postsynaptic currents (EPSCs) were recorded with or without prior stimulation of the inhibitor using a loose macropatch clamp technique at atmospheric pressure and at 6.9 MPA helium pressure. High pressure reduced the mean EPSC amplitude and variance, decreased the quantal content (m), but did not affect the quantum current (q). Pressure shifted the median of the amplitude histogram to the left by 1-2 q. Under normal pressure conditions, presynaptic inhibition and low (Ca2+)0 induced similar effects.