Calcium-Activated Hydrolysis of Triphosphoinositide in Synaptosomes
Dawson (1954) first showed that the polyphosphoinositides of brain were more readily labelled with 32P than the other phospholipids. Diphosphoinositide and triphosphoinositide are found in myelin and other plasma membrane structures of nerve tissue. Turnover of the 4- and 5-phosphates of triphosphoinositide is very rapid and until recently has seemed more important in axons than at synapses (Hawthorne & Kai, 1970). Acetylcholine, for instance, stimulates incorporation of phosphate into the phosphatidylinositol of synaptosomes from brain cortex but has a smaller, inhibitory effect on incorporation into the polyphosphoinositides (Schacht & Agranoff, 1972). However, Abdel-Latif et al. (1977) have shown recently that triphosphoinosítide of rabbit iris muscle is hydrolysed as a result of muscarinic cholinergic stimulation.
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- Hawthorne, J.N. and Kai, M. (1970) in Handbook of Neurochemistry, Vol. 3 (A. Lajtha, ed.) pp. 491–508. Plenum Press, New York.Google Scholar