Effect of fluoxetine treatment on electrical activity CGCs. A. Examples of intracellular recording of spontaneous electrical activity in CGCs of control (CS-DS) and conditioned (CS-UCS) senior animals treated with vehicle only (−Fluoxetine) or with fluoxetine (+ Fluoxetine). B. Average number of spontaneous action potentials of CGCs in vehicle only and fluoxetine treated conditioned and control animals. Fluoxetine caused a significant increase in the number of spontaneous action potentials but only in CGCs from conditioned (CS-UCS) animals. No significant effect on electrical activity was observed in fluoxetine treated unconditioned control animals (CS-DS) or vehicle treated conditioned and unconditioned animals. C. CGC resting membrane potential of fluoxetine treated snails was significantly more depolarized compared with vehicle only treated animals. Behavioural conditioning had no effect on resting membrane potential in both treatments. * = p < 0.05, *** = p < 0.001, ns = non-significant.