As means to determine the effect of the CRE injection detailed in Figure 3,
Kandel and colleagues measured the e.p.s.p.'s (excitatory post synaptic
potentials) of the sensory neuron on to the L7 motor neuron in response to
serotonin treatment. The top portion (a) of the figure shows the e.p.s.p.
measurements 24 hours after the application of serotonin. Compared to the
un-injected and non-specific nucleotide injected samples, the neurons
injected with the CRE oligonucleotide had a significantly lower e.p.s.p.
amplitude. This means that long-term facilitation is hindered by the
injection of the CRE oligonucleotide. The amplitude of the e.p.s.p. measured after serotonin was just applied (short term facilitation) was not affected by CRE injection. Part (b) shows graphically that the e.p.s.p. amplitude for long-term facilitation was affected by the injection of the CRE oligonucleotide but not by the injection of non-specific oligonucleotide or enhancer sequences (heat shock element or NF kappa beta). Part (c) shows schematically that CRE injection did not have an effect on the e.p.s.p. amplitude of short-term facilitation.