Inositol 1,4,5-trisphosphate induced mobilization of Ca2+ from rat brain synaptosomes.
Inositol 1,4,5-trisphosphate (IP3) was found to release Ca2+ from presynaptic nerve endings (synaptosomes) made permeable with saponin. ATP-dependent Ca2+ uptake was carried out until equilibrium was reached. Addition of IP3 produced a rapid release of Ca2+, which was complete within 60 sec, followed by Ca2+ reaccumulation to the original level in 5-7 min. Cholinergic receptor stimulation with muscarine also produced a similar Ca2+ release from synaptic endoplasmic reticulum. Ca2+ release by IP3 was not detectable in the absence of the mitochondrial inhibitors oligomycin or sodium azide. Reaccumulation of Ca2+ was prevented by the presence of vanadate, a potent inhibitor of Ca2+/Mg2+ ATPase. Half maximal and near complete release of Ca2+ took place at 0.4 microM and 3 microM IP3 concentrations, respectively. These studies demonstrate for the first time IP3 mobilization of Ca2+ from endoplasmic reticulum within synaptic plasma membranes.
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000494:pharmacology*; D007700:Kinetics; D008297:Male; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011950:Receptors, Cholinergic / Q000502:physiology; D012503:Saponins / Q000494:pharmacology; D013403:Sugar Phosphates / Q000494:pharmacology*; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*
D007295:Inositol Phosphates; D011950:Receptors, Cholinergic; D012503:Saponins; D013403:Sugar Phosphates; D015544:Inositol 1,4,5-Trisphosphate; D000255:Adenosine Triphosphate; D002118:Calcium