The rare earth lanthanide gadolinium (Gd3+), in concentrations ranging from 1 to 100 μM, reduced the elevation of intracellular Ca2+ concentration [Ca2+]i, monitored by means of the fluorescent probe fura-2. It also decreased the influx of 45Ca2+ through voltage sensitive calcium channels (VSCC), induced by 55 mM K+ in Percoll-purified brain synaptosomes. By contrast, Gd3+ (0.1-30 μM) did not interfere with Na+-dependent 45Ca2+ uptake, a process which expresses Na+Ca2+ exchange activity. The aminoglycoside neomycin displayed a similar pattern of activity although at higher concentrations (300-1000 μM). At the same range of concentrations (100 and 300 μM), the phenylalkylamine, verapamil, blocked both Ca2+ entry through VSCC and Ca2+ influx through the Na+Ca2+ exchanger. Finally, nimodipine failed to prevent 45Ca2+ influx in either case, and fura-2 monitored [Ca2+]i elevation induced by high K+- or Na+-dependent 45Ca2+ uptake. Collectively, the data obtained in the present study indicate that Gd3+ and neomycin can be considered to be valid pharmacological tools for selective blocking of VSCC in cerebral nerve terminals, without any concomitant interference with the Na+Ca2+ antiporter, whereas the inhibitory action of verapamil does not discriminate between Ca2+ entry through VSCC or the antiporter.
|Number of pages||7|
|Journal||European Journal of Pharmacology: Molecular Pharmacology|
|Publication status||Published - Apr 15 1993|
- Brain synaptosomes
- Voltage-sensitive Ca channels
ASJC Scopus subject areas