To determine the role of calcium in intracellular calcium, [Ca2+]i, oscillations in cultured LHRH neurons. As a step in studying the mechanism of LHRH pulse generation, we examined the role of Ca2+ in [Ca2+]i oscillations using cultured LHRH neurons derived from the embryonic olfactory placode. 1) Exposing cells to K+ (28 & 56mM) stimulated [Ca2+]i oscillations in a dose responsive manner; 2) Exposing cells to low Ca2+ (20 nM) buffer solution or the Ca2+ chelator, EGTA, suppressed [Ca2+]i oscillations; 3) [Ca2+]i oscillations were stimulated by the L-type Ca2+ channel stimulant, Bay K 8644 (1 5M), while they were suppressed by the L-type Ca2+ channel blockers, nifedipine (1 5M) and nimodipine (1 5M), but not by the N-type channel blocker, (-conotoxin (1 5M); 4) The intracellular Ca2+ stimulant, ryanodine (1 5M) stimulated [Ca2+]i oscillations; 5) Carbonyl-cyanide-P-trifluoromethoxy-phenyl hydrazone (FCCP, 1 (M), a mitochondrial Ca2+ mobilizer, stimulated [Ca2+]i oscillations; 6) Different types of K+ channel blockers induced different changes in [Ca2+]i oscillations. These results indicate that 1) depolarization with K+, induces [Ca2+]i oscillations, 2) [Ca2+]i oscillations are influenced by the presence of extracellular Ca2+, 3) Ca2+ enters the cell via L-type channels, but not N-type channels, 4) mobilization of intracellular Ca2+ is important for [Ca2+]i oscillations, and 5) different types of K+ channels may play a specific role in the [Ca2+]i oscillations. It is concluded that influx of Ca2+, through L-type Ca2+ channels, activated by K+ channel opening, generates [Ca2+]i oscillations, but mobilization of intracellular Ca2+ also appears to contribute to [Ca2+]i oscillations in cultured LHRH neurons. FUTURE DIRECTIONS We will examine the mechanism of intracellular Ca2+ oscillations. KEY WORDS intracellular Ca2+ signaling, Ca2+ oscillations, LHRH neurons, olfactory placode. FUNDING NIH HD15433 & RR00167 PUBLICATIONS Fernandez, D.L., Keen, K.L., Luchansky, L.L., and Terasawa., E. The role of Ca2+ in intracellular Ca2+ oscillations in cultured LHRH neurons derived from embryonic olfactory placode of the rhesus monkey. Abstracts of the 28th Annual Meeting of the Society for Neuroscience 24 270 (No. 110.4), 1998. Terasawa, E., Keen, K.L., and Fernandez, D.L. Periodical intracellular Ca2+ oscillations and pulsatile LHRH release in cultured LHRH neurons from the embryonic olfactory placode in the rhesus monkey. Proceeding of the 4th International Congress of Neuroendocrinology, held October 11-15, 1998 at Kitakyushu, Japan. pp.417 (No. R22).
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