title: Calcium buffering and clearance in spider mechanosensory neurons.
abstract: Spider VS-3 mechanoreceptor neurons have a low-voltage-activated Ca2+ current that raises intracellular calcium concentration [Ca2+] when they are depolarized by agonists of GABAA receptors or fire action potentials. The Ca2+ rise produces negative feedback by modulating the mechanoreceptor current and regulates Ca2+- and voltage-activated K+ currents. However, nothing is known about Ca2+ buffering in VS-3 neurons. Dynamic changes in VS-3 neuron intracellular [Ca2+] were measured using the fluorescent Ca2+ indicator Oregon Green BAPTA-1 (OG488) to understand Ca2+ buffering and clearance. Intracellular OG488 concentration increased slowly over more than 2 h as it diffused through a sharp intracellular microelectrode and spread through the cell. This slow increase was used to measure endogenous Ca2+ buffering and clearance by the added buffer technique, with OG488 acting as both added exogenous buffer and Ca2+ indicator. [Ca2+] was raised for brief periods by regular action potential firing, produced by pulsed electric current injection through the microelectrode. The resulting rise and fall of [Ca2+] were well fitted by the single compartment model of Ca2+ dynamics. With earlier ratiometric [Ca2+] estimates, these data gave an endogenous Ca2+ binding ratio of 684. Strong Ca2+ buffering may assist these neurons to deal with rapid changes in mechanical inputs.
authors.affiliation: Department of Physiology and Biophysics, Dalhousie University, PO BOX 15000, Halifax, NS, B3H 4R2, Canada.
authors.forename: Joscha
authors.initials: J
authors.lastname: Schmitz
authors.forename: Ulli
authors.initials: U
authors.lastname: Höger
authors.forename: Päivi H
authors.initials: PH
authors.lastname: Torkkeli
authors.forename: Andrew S
authors.initials: AS
authors.lastname: French
mesh_terms: D000200:Action Potentials; D000814:Aniline Compounds; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D004558:Electric Stimulation; D025461:Feedback, Physiological; D005452:Fluoresceins; D005456:Fluorescent Dyes; D008465:Mechanoreceptors / Q000378:metabolism*; D040542:Mechanotransduction, Cellular; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D013112:Spiders / Q000166:cytology / Q000378:metabolism*; D013997:Time Factors
chemical_list: D000814:Aniline Compounds; D005452:Fluoresceins; D005456:Fluorescent Dyes; C503942:Oregon green 488 BAPTA-1; D002118:Calcium