title: Presynaptic control of rapid estrogen fluctuations in the songbird auditory forebrain.
abstract: Within the CNS of vertebrates, estrogens can directly modulate neural circuits that govern a wide range of behaviors, including feeding, spatial navigation, reproduction, and auditory processing. The rapid actions of estrogens in brain (seconds to minutes) have become well established, but it is unclear how estrogens are synthesized and released within restricted temporal and spatial domains in neural circuits. Anatomical localization of the estrogen synthesis enzyme (aromatase) within presynaptic terminals suggests that neuroestrogens can be synthesized directly at the neuronal synapse. A consequent prediction follows that synaptic estrogen production is controlled via classical electrochemical events in neurons. Here, we present evidence that acute fluctuations in local neuroestrogen levels in the forebrain of the zebra finch depend on calcium influx within presynaptic terminals. In vivo experiments using microdialysis linked to a sensitive estrogen ELISA showed that local forebrain neuroestrogens were both suppressed by potassium-evoked excitation and upregulated during 30 min periods of extracellular calcium depletion in a region enriched with presynaptic aromatase. Furthermore, potassium-evoked changes in local neuroestrogens were blocked by targeted delivery of the voltage-gated calcium channel blocker ω-conotoxin GVIA. Together, these experiments indicate that neuroestrogens are controlled by specific, depolarization-sensitive, calcium-dependent events within forebrain presynaptic terminals.
authors: Department of Integrative Biology and Physiology, and Laboratory of Neuroendocrinology, Brain Research Institute, University of California, Los Angeles, Los Angeles, California 90095, USA. healey@cns.umass.edu
authors: Luke
authors: L
authors: Remage-Healey
authors: Stephanie
authors: S
authors: Dong
authors: Nigel T
authors: NT
authors: Maidment
authors: Barney A
authors: BA
authors: Schlinger
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D004967:Estrogens / Q000378:metabolism*; D008297:Male; D017551:Microdialysis / Q000379:methods; D011188:Potassium / Q000494:pharmacology; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism*; D016548:Prosencephalon / Q000166:cytology* / Q000378:metabolism; D020308:Songbirds; D018709:Statistics, Nonparametric; D013569:Synapses / Q000187:drug effects / Q000378:metabolism*; D020866:omega-Conotoxin GVIA / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D004967:Estrogens; D020866:omega-Conotoxin GVIA; D011188:Potassium