title: The real catecholamine content of secretory vesicles in the CNS revealed by electrochemical cytometry.
abstract: Resolution of synaptic vesicle neurotransmitter content has mostly been limited to the study of stimulated release in cultured cell systems, and it has been controversial as to whether synaptic vesicle transmitter levels are saturated in vivo. We use electrochemical cytometry to count dopamine molecules in individual synaptic vesicles in populations directly sampled from brain tissue. Vesicles from the striatum yield an average of 33,000 dopamine molecules per vesicle, an amount considerably greater than typically measured during quantal release at cultured neurons. Vesicular content was markedly increased by L-DOPA or decreased by reserpine in a time-dependent manner in response to in vivo administration of drugs known to alter dopamine release. We investigated the effects of the psychostimulant amphetamine on vesicle content, finding that vesicular transmitter is rapidly depleted by 50% following in vivo administration, supporting the "weak base hypothesis" that amphetamine reduces synaptic vesicle transmitter and quantal size.
authors.affiliation: Department of Chemistry, Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Donna M
authors.initials: DM
authors.lastname: Omiatek
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Bressler
authors.forename: Ann-Sofie
authors.initials: AS
authors.lastname: Cans
authors.forename: Anne M
authors.initials: AM
authors.lastname: Andrews
authors.forename: Michael L
authors.initials: ML
authors.lastname: Heien
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Ewing
mesh_terms: D000661:Amphetamine / Q000494:pharmacology; D000818:Animals; D002490:Central Nervous System / Q000187:drug effects / Q000378:metabolism*; D000697:Central Nervous System Stimulants / Q000494:pharmacology; D004298:Dopamine / Q000032:analysis*; D055664:Electrochemical Techniques / Q000295:instrumentation / Q000379:methods*; D005260:Female; D007980:Levodopa / Q000494:pharmacology; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D010316:Particle Size; D012110:Reserpine / Q000494:pharmacology; D013572:Synaptic Vesicles / Q000378:metabolism*
chemical_list: D000697:Central Nervous System Stimulants; D007980:Levodopa; D012110:Reserpine; D000661:Amphetamine; D004298:Dopamine