ISSN:
1471-4159
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
Abstract: Pinched-off presynaptic nerve terminals (synaptosomes) possess significant regulatory volume increase (RVI) and regulatory volume decrease (RVD) capabilities. Following a swelling induced by a hypotonic challenge, the synaptosomes regulate their volume and adjust it, in 2 min, to within 5% of its initial value (RVD) at an initial rate of -0.77 ± 0.10%/s (mean ± SEM). Following a shrinking induced by a hypertonic challenge, the synaptosomes also regulate their volume at an initial rate of 0.18 ± 0.02%/s (RVI), resulting in a new steady state, reached within 5–10 min, with a synaptosomal volume below the original volume. The omission of Na+ or K+ ions from the extrasynaptosomal medium reduces the initial rate of RVI by 72.5 and 66.5%, respectively. The “loop diureties” bumetanide and furosemide significantly inhibited the RVI of the synaptosomes. In contrast, ouabain, amiloride, or 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid did not have any significant effect on RVI parameters. Furthermore, bumetanide-sensitive 86Rb uptake by rat brain synaptosomes was stimulated threefold by a hypertonic perturbation of 30%. Thus we conclude that the RVI of synaptosomes is mainly due to a stimulation of the Na+, K+, Cl− co-transport system induced by the synaptosomal shrinking following the hypertonic challenge.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1471-4159.1990.tb05795.x
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