Interaction between Ca2+ release from inositol trisphosphate sensitive stores and Ca2+ entry through neuronal Ca2+ channels expressed in Xenopus oocyte.
Rat cerebellar RNA injected into Xenopus oocytes leads to the expression of putative P-type voltage-dependent Ca2+ channels (VDCCs). The monitoring of intracellular Ca2+ variations by recording the Ca2+ dependent chloride current in voltage clamped oocytes indicates that activation of these Ca2+ channels by depolarization gives rise to two distinct components of cytosolic Ca2+ elevation. If the early component (T1) can be directly attributed to the Ca2+ entry through VDCCs, the second delayed one (T2) is related to a Ca2+ release from InsP3 sensitive stores activated following Ca2+ entry. Modifications of cytosolic Ca2+ by direct injection of Ca2+ into oocytes or by increasing the Ca2+ influx through VDCCs suggest that the Ca2+ release from intracellular InsP3 sensitive stores can be modulated in a differential manner. Namely, discrete elevations of cytosolic Ca2+ switch on the Ca2+ release whereas higher Ca2+ concentrations dampen the release. These results suggest a functional coupling between P-type VDCCs and InsP3 receptors.
Laboratoire de Neurobiologie Cellulaire, UFR des Sciences exactes et fondamentales, Université de Picardie Jules Verne, Amiens, France.
F
F
Fournier
P
P
Navarre
F
F
Matifat
C
C
Vilbert
T
T
Colin
P
P
Guilbault
G
G
Brule
D
D
Marlot
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000235:genetics / Q000502:physiology*; D002531:Cerebellum / Q000737:chemistry; D015870:Gene Expression; D066298:In Vitro Techniques; D007295:Inositol Phosphates / Q000502:physiology*; D017136:Ion Transport; D009865:Oocytes / Q000737:chemistry; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D014982:Xenopus laevis
D015220:Calcium Channels; D007295:Inositol Phosphates; D012333:RNA, Messenger; D002118:Calcium