Fig. 2. Serotonin-mediated membrane potential changes of nonspiking interneurones (ns int). (A) Serotonin-mediated hyperpolarization of a nonspiking interneurone. Bath application of serotonin (5-HT; 100 µmol l^-1) for 3 min (indicated by thick bar) inhibited the motor neurone and elicited a hyperpolarization of the nonspiking interneurone. (B) Serotonin-mediated depolarization of a nonspiking interneurone. Bath application of 100 µmol l^-1 serotonin for 3 min (indicated by thick bar) mediated a membrane depolarization of the nonspiking interneurone and suppressed the tonic discharge of the reductor motor neurone (red mn). (C) Brief application (100ms) of 0.1 µmol l^-1 serotonin caused a long-lasting membrane hyperpolarization of the nonspiking interneurone. (D) Brief application (100ms) of 0.1 µmol l^-1 serotonin caused a membrane depolarization. The dashed line indicates the resting membrane potential level.

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