Injection of digitally synthesized synaptic conductance transients to measure the integrative properties of neurons.

A novel technique was developed for injecting a time-varying conductance into a neuron, to allow quantitative measurement of the processing of synaptic inputs. In current-clamp recording mode, the membrane potential was sampled continuously and used to calculate and update the level of injected current within 60 microseconds, using a real-time computer, so as to mimic the electrical effect of a given conductance transient. Cellular responses to synthetic conductance transients modelled on the fast (non-N-methyl-D-aspartate) phase of the glutamatergic postsynaptic potential were measured in cultured rat hippocampal neurons.