Figure 7.

Intermediate-term facilitation induced by combined 5-HT and sensory neuron firing. A, Postsynaptic potentials in motor neurons elicited with single action potentials in sensory neurons in cocultures were compared with baseline EPSPs (Pre) 30 or 60 min after no treatment (Test alone), after a 5 min application of 5-HT alone or four trains of action potentials in the sensory neuron in the absence of 5-HT (Stim), or after combined 5-HT and stimulation of the sensory neuron. Only combined 5-HT and firing resulted in significant facilitation of the EPSP. Calibration: 20 mV, 25 ms. B, Summary of experiments like those in A, showing that only the combination of 5-HT and firing in the sensory neurons gives rise to intermediate-term facilitation at 30 and 60 min time points (p < 0.001 for both times; two-way ANOVA).