title: Calcium transients recorded with arsenazo III in the presynaptic terminal of the squid giant synapse.
abstract: Transient changes in free intracellular Ca2+ concentration were monitored in the presynaptic terminal of the giant synapse of the squid, by means of the Ca2+-sensitive dye arsenazo III. Calibration experiments showed a linear relation between the amount of Ca2+ injected by iontophoresis into the terminal, and the peak size of the arsenazo light absorbance record. A light signal could be detected on tetanic stimulation of the presynaptic axon bathed in sea water containing 45 mM Ca2+. During a 1 s tetanus the light signal rose approximately linearly, even though transmitter release declined rapidly and the light signal subsequently declined with a half-time of 2-6 s. The Ca2+ transient elicited by single nerve impulses was recorded by signal averaging, and showed a time course very much slower than the duration of transmitter release.
mesh_terms: D000818:Animals; D001150:Arsenazo III; D001369:Axons / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D049832:Decapodiformes; D004553:Electric Conductivity; D004558:Electric Stimulation; D008027:Light; D013569:Synapses / Q000502:physiology*
chemical_list: D001150:Arsenazo III; D002118:Calcium