A fast activating presynaptic reuptake current during serotonergic transmission in identified neurons of Hirudo.
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.
Department of Neurophysiology, Max Planck Institute for Psychiatry, Planegg-Martinsried, Germany.
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D015116:5,7-Dihydroxytryptamine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D005453:Fluorescence; D007700:Kinetics; D007865:Leeches; D009474:Neurons / Q000502:physiology*; D010775:Photic Stimulation; D012701:Serotonin / Q000494:pharmacology / Q000502:physiology*; D012964:Sodium / Q000037:antagonists & inhibitors / Q000502:physiology; D013569:Synapses / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*; D015031:Zimeldine / Q000494:pharmacology
D015116:5,7-Dihydroxytryptamine; D012701:Serotonin; D015031:Zimeldine; D012964:Sodium; D002118:Calcium