Premium
Histamine‐induced calcium entry in rat cerebellar astrocytes: evidence for capacitative and non‐capacitative mechanisms
Author(s) -
Jung Silke,
Pfeiffer Fatima,
Deitmer Joachim W.
Publication year - 2000
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2000.00549.x
Subject(s) - histamine , cyclopiazonic acid , extracellular , intracellular , mepyramine , chemistry , calcium , fura 2 , biophysics , medicine , nifedipine , agonist , calcium in biology , endocrinology , antagonist , receptor , biology , biochemistry , cytosol , enzyme
1 We have investigated the effects of histamine on the intracellular calcium concentration ([Ca 2+ ] i ) of cultured rat cerebellar astrocytes using fura‐2‐based Ca 2+ imaging microscopy. 2 Most of the cells responded to the application of histamine with an increase in [Ca 2+ ] i which was antagonized by the H 1 receptor blocker mepyramine. When histamine was applied for several minutes, the majority of the cells displayed a biphasic Ca 2+ response consisting of an initial transient peak and a sustained component. In contrast to the initial transient [Ca 2+ ] i response, the sustained, receptor‐activated increase in [Ca 2+ ] i was rapidly abolished by chelation of extracellular Ca 2+ or addition of Ni 2+ , Mn 2+ , Co 2+ and Zn 2+ , but was unaffected by nifedipine, an antagonist of L‐type voltage‐activated Ca 2+ channels. These data indicate that the sustained increase in [Ca 2+ ] i was dependent on Ca 2+ influx. 3 When intracellular Ca 2+ stores were emptied by prolonged application of histamine in Ca 2+ ‐free conditions, Ca 2+ re‐addition after removal of the agonist did not lead to an ‘overshoot’ of [Ca 2+ ] i indicative of store‐operated Ca 2+ influx. However, Ca 2+ stores were refilled despite the absence of any substantial change in the fura‐2 signal. 4 Depletion of intracellular Ca 2+ stores using cyclopiazonic acid in Ca 2+ ‐free saline and subsequent re‐addition of Ca 2+ to the saline resulted in an increase in [Ca 2+ ] i that was significantly enhanced in the presence of histamine. 5 The results suggest that besides capacitative mechanisms, a non‐capacitative, voltage‐independent pathway is involved in histamine‐induced Ca 2+ entry into cultured rat cerebellar astrocytes.