Activity-dependent vesicular monoamine transporter-mediated depletion of the nucleus supports somatic release by serotonin neurons.
Packaging by the vesicular monoamine transporter (VMAT) is essential for mood-controlling serotonin transmission but has not been assayed during activity. Here, two-photon imaging of the fluorescent serotonin analog 5,7-dihydroxytryptamine and three-photon imaging of endogenous serotonin were used to study vesicular packaging as it supports release from the soma of serotonin neurons. Glutamate receptor activation in dorsal raphe brain slice evoked somatic release that was mediated solely by vesicle exocytosis. This release was accompanied by VMAT-mediated serotonin depletion from the nucleus, a large compartment free of monoaminergic degradation pathways that has not been implicated in neurotransmission previously. Finally, while some monoamine packaged at rest was held in reserve, monoamine packaged during stimulation was released completely. Hence, somatic vesicles loaded by VMAT during activity rapidly undergo exocytosis. In the absence of active zones and with limited neurotransmitter reuptake, somatic release by serotonin neurons is supported by recruitment from a large pool of extravesicular serotonin in the nucleus and cytoplasm, and preferential release of the newly packaged transmitter.
Colgan
Lesley A
LA
Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
Putzier
Ilva
I
Levitan
Edwin S
ES
D015116:5,7-Dihydroxytryptamine / Q000494:pharmacology; D000818:Animals; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology; D008297:Male; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D016716:PC12 Cells; D011903:Raphe Nuclei / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism*; D050493:Vesicular Monoamine Transport Proteins / Q000502:physiology*
D050493:Vesicular Monoamine Transport Proteins; D015116:5,7-Dihydroxytryptamine; D012701:Serotonin