ISSN:
1471-4159
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
Abstract: In synaptosomes prepared from rat cerebral cortex, free cytosolic calcium concentration ([Ca2+]i) was measured using the fluorescent dye fura-2, Incubation of fura-2-loaded synaptosomes with carbachol increased [Ca2+]i in a dose-dependent manner (1–1,000 μM), with a maximum response of 22 × 2% at approximately 100 μM and an EC50 (calculated concentration producing 50% of the maximum response) of 30 μM The effect of carbachol (100 μM) on [Ca2+], was antagonised by atropine, but not by hexamethonium (10 μM). The calculated concentration of atropine needed for 50% inhibition (IC50) was 260 nM. The rise in [Ca2+]i produced by carbachol was reduced in the absence of extrasynaptosomal Ca2+ and effectively blocked by the L-type calcium channel blocker nifedipine (with an IC50 of 29 nM). The response to carbachol was reduced if the synaptosomes were preincubated with the protein kinase inhibitors H7 [1-(5-isoquinolinylsulfonyl)-2-methylpiperazine] (from 17% in the solvent control to 4%) and staurosporine (from 20% in the solvent control to 3%). These results show that stimulation of muscarinic acetylcholine receptors in synaptosomes increases [Ca2+]i by protein kinase-dependent activation of 1,4-dihydropyridinesensitive calcium channels.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1471-4159.1990.tb08843.x
