Release of LHRH is linearly related to the time integral of presynaptic Ca2+ elevation above a threshold level in bullfrog sympathetic ganglia.
To study the Ca2+ dependency of luteinizing hormone-releasing hormone (LHRH) release in the bullfrog sympathetic ganglia, a method was developed to fill the preganglionic nerve terminal boutons with membrane-impermeant fura-2. We found that as stimulation frequency increased from 0.5 to 40 Hz, the peak [Ca2+]i ([Ca2+]p) and the rate of rise in [Ca2+]i increased, the decay of [Ca2+]i transients followed up to three exponentials, and release of LHRH was linearly related to integral of ([Ca2+]i--[Ca2+]t)dt. The threshold level of [Ca2+]i for LHRH release for a given set of boutons on a C cell, [Ca2+]t, was estimated by the [Ca2+]p evoked by 0.5 Hz stimulation that does not induce LHRH release.
Peng
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Department of Molecular and Cell Biology, University of California, Berkeley 94720.
Zucker
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RS
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004056:Differential Threshold; D005260:Female; D016257:Fura-2; D005728:Ganglia, Sympathetic / Q000378:metabolism*; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D008297:Male; D009411:Nerve Endings / Q000378:metabolism; D009994:Osmolar Concentration; D011892:Rana catesbeiana; D013569:Synapses / Q000378:metabolism*; D013997:Time Factors
D007987:Gonadotropin-Releasing Hormone; D002118:Calcium; D016257:Fura-2