Regulation of calcium currents and secretion by magnesium in crustacean peptidergic neurons

The effect of varying the external Mg2+ concentration on Ca2+ currents through voltage-operated Ca2+ channels has been examined with the patch-clamp technique in acutely isolated neuronal somata from the X-organ-sinus gland (XOSG) of the crab, Cardisoma carnifex. Neurons from this neurosecretory sys...

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Bibliographic Details
Published in:Invertebrate neuroscience 1995-12, Vol.1 (3), p.215-221
Main Authors: Richmond, J E, Sher, E, Keller, R, Haylett, B, Reichwein, B, Cooke, I M
Format: Article
Language:English
Subjects:
Animals
Arthropod Proteins
Brachyura
Calcium Channels - drug effects
Calcium Channels - metabolism
Calcium Channels - physiology
Cardisoma carnifex
Electric Conductivity
Invertebrate Hormones
Magnesium - pharmacology
Marine
Nerve Tissue Proteins - metabolism
Neurons - drug effects
Neurons - metabolism
Neurons - physiology
Neurosecretory Systems - cytology
Neurosecretory Systems - metabolism
Osmolar Concentration
Patch-Clamp Techniques
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Summary:The effect of varying the external Mg2+ concentration on Ca2+ currents through voltage-operated Ca2+ channels has been examined with the patch-clamp technique in acutely isolated neuronal somata from the X-organ-sinus gland (XOSG) of the crab, Cardisoma carnifex. Neurons from this neurosecretory system were selected for morphology associated with crustacean hyperglycemic hormone (CHH) content. In parallel, the effects of Mg2+ concentration on K(+)-evoked secretion of CHH from isolated, intact XOSGs have been assayed by ELISA. At physiological Ca2+ levels the high-voltage-activated Ca2+ currents were attenuated with increasing Mg2+ concentration, with 50% inhibition at approximately 75 mM. Mg2+ block was voltage-dependent, relief from block occurring with increasing depolarization. Thus, in 24 mM Mg2+ inhibition of the Ca2+ current was approximately 55% at -10 mV. Secretion of CHH varied almost linearly with the log of Mg2+ concentration; in 2.4 mM Mg2+ it was double that in 24 mM Mg2+ and almost completely inhibited in 100 mM. Thus, Mg2+ produces a parallel inhibition of Ca2+ currents and CHH secretion and may play a role as a physiological modulator of neuronal activity and secretion in the XOSG of these crabs.
ISSN:1354-2516
1439-1104
DOI:10.1007/BF02211023