Biophysical Journal 61: 19-30 (1992)
© 1992 the Biophysical Society

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Lindau, M Articles by Nordmann, J J Search for Related Content PubMed PubMed Citation Articles by Lindau, M Articles by Nordmann, J J

Depolarization, intracellular calcium and exocytosis in single vertebrate nerve endings.

Biophysics Group, Freie Universität Berlin, Germany.

ABSTRACT

We have investigated the temporal relationship between depolarization, elevation of [Ca2+]i and exocytosis in single vertebrate neuroendocrine nerve terminals. The change of [Ca2+]i and vasopressin release were measured with a time resolution of less than 1 s in response to K(+)-induced depolarization. Exocytosis was also monitored in the whole-terminal patch-clamp configuration by time resolved capacitance measurements while [Ca2+]i was simultaneously followed by fura-2 fluorescence measurements. In intact as well as patch-clamped nerve terminals sustained depolarization leads to a sustained rise of [Ca2+]i. The rate of vasopressin release from intact nerve terminals rises in parallel with [Ca2+]i but then declines rapidly towards basal (t1/2 approximately 15 s) despite the maintained high [Ca2+]i indicating that only a limited number of exocytotic vesicles can be released. We demonstrate that in nerve terminals exocytosis can be followed during step depolarization by capacitance measurements. The capacitance increase starts instantaneously whereas [Ca2+]i rises with a half time of several hundred milliseconds. An instantaneous steep capacitance increase is followed by a slow increase with a slope of 25-50 fF/s indicating the sequential fusion of predocked and cytoplasmic vesicles. During depolarization the capacitance slope declines to zero with a similar time course as the vasopressin release indicating a decrease in exocytotic activity. Depolarization per se in the absence of a sufficient rise of [Ca2+]i does not induce exocytosis but elevation of [Ca2+]i in the absence of depolarization is as effective as in its presence. The experiments suggest that a rapid rise of [Ca2+]i in a narrow region beneath the plasma membrane induces a burst of exocytotic activity preceding the elevation of bulk [Ca2+]i in the whole nerve terminal.

This article has been cited by other articles:

				W. Ouyang and H. C. Hemmings Jr. Depression by Isoflurane of the Action Potential and Underlying Voltage-Gated Ion Currents in Isolated Rat Neurohypophysial Nerve Terminals J. Pharmacol. Exp. Ther., February 1, 2005; 312(2): 801 - 808. [Abstract] [Full Text] [PDF]

				M. Lindau Synaptotagmin Function Illuminated J. Gen. Physiol., August 25, 2003; 122(3): 251 - 254. [Full Text] [PDF]

				W. Ouyang, G. Wang, and H. C. Hemmings Jr Isoflurane and Propofol Inhibit Voltage-Gated Sodium Channels in Isolated Rat Neurohypophysial Nerve Terminals Mol. Pharmacol., August 1, 2003; 64(2): 373 - 381. [Abstract] [Full Text] [PDF]

				A. Llobet, A. Cooke, and L. Lagnado Exocytosis at the Ribbon Synapse of Retinal Bipolar Cells Studied in Patches of Presynaptic Membrane J. Neurosci., April 1, 2003; 23(7): 2706 - 2714. [Abstract] [Full Text] [PDF]

				G. Wang, G. Dayanithi, R. Newcomb, and J. R. Lemos An R-Type Ca2+ Current in Neurohypophysial Terminals Preferentially Regulates Oxytocin Secretion J. Neurosci., November 1, 1999; 19(21): 9235 - 9241. [Abstract] [Full Text] [PDF]

				T. E. Fisher and J. M. Fernandez Pulsed Laser Imaging of Ca2+ Influx in a Neuroendocrine Terminal J. Neurosci., September 1, 1999; 19(17): 7450 - 7457. [Abstract] [Full Text] [PDF]

				K. I. Rusin, D. R. Giovannucci, E. L. Stuenkel, and H. C. Moises kappa -Opioid Receptor Activation Modulates Ca2+ Currents and Secretion in Isolated Neuroendocrine Nerve Terminals J. Neurosci., September 1, 1997; 17(17): 6565 - 6574. [Abstract] [Full Text] [PDF]

				L von Ruden and E Neher A Ca-dependent early step in the release of catecholamines from adrenal chromaffin cells Science, November 12, 1993; 262(5136): 1061 - 1065. [Abstract] [PDF]

				M Lindau, O Nusse, J Bennett, and O Cromwell The membrane fusion events in degranulating guinea pig eosinophils J. Cell Sci., January 1, 1993; 104(1): 203 - 210. [Abstract] [PDF]

				E Neher Ion channels for communication between and within cells Science, April 24, 1992; 256(5056): 498 - 502. [PDF]