A simplified electronic circuit for combined single-cell stimulation and recording using loose cell-attached electrodes

While tight-seal patch clamp recordings have found wide use in neuroscience and in other fields, the requirement to replace the glass pipette after every attempted recording represents an impediment to high throughput studies such as searching for monosynaptically connected pairs of neurons. Loose cell-attached recording was introduced in 2000 to circumvent this problem since it enabled combined recording and stimulation of visually-identified neurons without necessitating a tight (gigaohm) seal. Since the stimulus voltages required to evoke action potentials through low resistance seals are beyond the capacity of most commercial amplifiers, Barbour and Isope introduced a variation of classic patch clamp amplifier circuit that is able to deliver stimulus voltages that are effective in triggering action potentials under the loose cell-attached patch clamp configuration. The present report presents the design and operation of a simpler amplifier that contains only two integrated circuits and is able to effectively stimulate and record action potentials in mitral cells in rodent olfactory bulb slices. The addition of an accessory analog gating circuit enables manual control of the stimulus voltage with pulse timing controlled by a digital output from a computer. This system may be useful in studies that require surveying many potential pairs of neurons for synaptic connections and for sampling and manipulating single-cell activity in in vivo electrophysiology experiments.