A fast activating presynaptic reuptake current during serotonergic transmission in identified neurons of Hirudo

Neuron. 1993 Apr;10(4):559-72. doi: 10.1016/0896-6273(93)90159-o.


An electrogenic serotonin (5-HT) uptake process was characterized in the serotonergic Retzius-P cell synapse of the leech, and the simultaneous activation of this presynaptic reuptake and the postsynaptic response was monitored during evoked transmitter release. A presynaptic, Na(+)-dependent inward current upon application of 5-HT was isolated at membrane potentials between -80 and +60 mV. Its identification as a transmitter uptake current was confirmed by monitoring accumulation of the autofluorescent 5-HT analog 5,7-dihydroxytryptamine during activation of this current. To study the kinetics of 5-HT reuptake in functional synapses, transmitter release was stimulated by flash photolysis of the Ca(2+)-caging DM-nitrophen. The results demonstrate that reuptake activates with a minimal delay of less than a millisecond during synaptic transmission. It acts as a rapid transmitter removal system to determine the time course of the postsynaptic response and monitors the kinetics of transmitter clearance at the synaptic site.

MeSH terms

  • 5,7-Dihydroxytryptamine / pharmacology
  • Animals
  • Calcium / pharmacology
  • Dose-Response Relationship, Drug
  • Electric Conductivity
  • Fluorescence
  • Kinetics
  • Leeches
  • Neurons / physiology*
  • Photic Stimulation
  • Serotonin / pharmacology
  • Serotonin / physiology*
  • Sodium / antagonists & inhibitors
  • Sodium / physiology
  • Synapses / physiology*
  • Synaptic Transmission / physiology*
  • Zimeldine / pharmacology


  • 5,7-Dihydroxytryptamine
  • Serotonin
  • Zimeldine
  • Sodium
  • Calcium