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.
Bruns
D
D
Department of Neurophysiology, Max Planck Institute for Psychiatry, Planegg-Martinsried, Germany.
Engert
F
F
Lux
H D
HD
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