The relationship between quantal content and delayed quantal release.
Following an endplate potential there is a period of elevated spontaneous quantal release, known as delayed release. We have estimated the relationship between evoked quantal release and delayed release in two ways. First, in a solution in which the Na+ was replaced with methylamine, the number of delayed release evoked by electronic depolarization of the nerve terminal changed little over a 30-fold range of output. Second, we varied [Ca2+]out stepwise in Na solution with added Mg2+ and measured delayed release and EPP amplitude at single junctions. Over much of the range, elevating the EPP amplitude many-fold increased delayed release only slightly, if at all. Our interpretation is that the effects of residual Ca2+ are not proportional to the amount of Ca2+ entering to trigger quantal release.
Department of Physiology and Biophysics, Health Sciences Center, SUNY, Stony Brook 11794, USA.
W
W
Van der Kloot
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J
Molgó
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D003080:Cold Temperature; D005071:Evoked Potentials / Q000187:drug effects; D008274:Magnesium / Q000494:pharmacology*; D009045:Motor Endplate / Q000187:drug effects*; D011789:Quantum Theory; D011894:Rana pipiens; D011898:Ranidae; D011930:Reaction Time / Q000187:drug effects*; D012964:Sodium / Q000494:pharmacology*
D012964:Sodium; D008274:Magnesium; D002118:Calcium