The top portion (a) of this figure is a phase contrast microscope image of the sensory-motor neuron culture system used to investigate whether CREBP is involved in long-term facilitation. Motor neuron L7 and two sensory neurons are present in the image. The bottom portion of the figure is a schematic representation of the procedure followed by Kandel and colleagues. The sensory neuron component was injected with either the specific double stranded CRE oligonucleotide (if this competes with binding for the CREBP-like protein, the protein might not be able to activate cAMP inducible genes), a control oligonucleotide (that would not compete with binding) or nothing at all (to make sure that the injection itself was not harming the cells). Finally, serotonin was applied to the neuron culture system to see if long term potentiation was produced, and the resulting e.p.s.p (excitatory post synaptic potentials) were measured.