Abstract |
1. The calyciform nerve terminals of chick ciliary ganglia were loaded with the calcium indicators calcium green 1 or fura-2. These were used to determine the change in calcium concentration in the terminal, [Ca2+]t, following short (10 impulses) and long (600 impulses) trains of high-frequency (30 Hz) stimulation. 2. Following a single impulse or a short train, the elevated [Ca2+]t declined along two exponentials with time constants similar to slow (F2) facilitation (0.52 s) and augmentation (4.0 s). After a long train elevated [Ca2+]t declined eventually along a single exponential with the time constant of post-tetanic potentiation (162 s). [Ca2+]t was not elevated through long-term potentiation. 3. Addition of Ba2+ (0.75 mM) to the extracellular solution slowed only the decline of [Ca2+]t associated with augmentation. The addition of the nitric oxide donor sodium nitroprusside did not affect [Ca2+]t following short or long trains. 4. Removal of extracellular calcium (buffered with EGTA) and the blockade of calcium channels with Cd2+ completely prevented the changes in [Ca2+]t. 5. The soma of ciliary ganglion cells were loaded with calcium green and the postganglionic nerves stimulated with a single impulse or a short train of impulses. Following stimuli, the elevated [Ca2+]t declined along a single exponential with a time constant similar to F2 facilitation with no augmentation component evident. 6. The results are discussed in terms of the hypothesis that each impulse in a train gives an equal increment of residual Ca2+ to a compartment for secretion and that Ca2+ is removed from the compartment by three first-order kinetics processes associated with F2 facilitation, augmentation and post-tetanic potentiation.
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Authors | K L Brain, M R Bennett |
Journal | The Journal of physiology
(J Physiol)
Vol. 489 ( Pt 3)
Issue Pt 3
Pg. 637-48
(Dec 15 1995)
ISSN: 0022-3751 [Print] England |
PMID | 8788930
(Publication Type: Journal Article)
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Chemical References |
- Calcium Channel Blockers
- Fluorescent Dyes
- Organic Chemicals
- Cadmium
- calcium green
- Barium
- Nitric Oxide
- Calcium
- Fura-2
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Topics |
- Animals
- Barium
(pharmacology)
- Cadmium
(pharmacology)
- Calcium
(metabolism)
- Calcium Channel Blockers
(pharmacology)
- Chick Embryo
- Electric Stimulation
- Fluorescent Dyes
- Fura-2
- Ganglia, Parasympathetic
(cytology, physiology)
- Long-Term Potentiation
(physiology)
- Microscopy, Fluorescence
- Nerve Endings
(physiology)
- Neuronal Plasticity
(physiology)
- Nitric Oxide
(pharmacology)
- Oculomotor Nerve
(cytology, drug effects, physiology)
- Organic Chemicals
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