Figure 2. Fast and slow EPSPs in a nitric oxide synthase immunoreactive descending interneuron.

A Synaptic potentials evoked by electrical stimulation of the mucosa. Upper trace: membrane potential response at resting membrane potential, stimulus applied to neighbouring mucosa. Inset shows the EPSP evoked with superimposed action potentials on an expanded time base (arrows). Lower trace: fast EPSP (arrow) evoked by the same stimulus when the membrane potential was hyperpolarized to prevent action potential firing and increase the driving potential for the inward current. B Left panels: the impaled neuron stained to reveal biocytin (red) in the cell body (upper) and part of its axon with a side-branch providing varicose endings in a more anal ganglion (lower). Centre panels: nNOS-immunoreactivity (green) of the same fields. Right panels: superimposed images showing that the impaled neuron and its processes are nNOS-immunoreactive (yellow/orange).