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A rise in the intracellular Ca2+ concentration of isolated rat supraoptic cells in response to oxytocin.
Author(s) -
Lambert R C,
Dayanithi G,
Moos F C,
Richard P
Publication year - 1994
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 - 10.1113/jphysiol.1994.sp020249
Subject(s) - oxytocin , thapsigargin , egta , vasopressin , extracellular , medicine , intracellular , endocrinology , chemistry , neuropeptide , supraoptic nucleus , biophysics , receptor , biology , calcium , biochemistry
1. Intracellular Ca2+ concentration ([Ca2+]i) was monitored in single cells isolated from adult rat supraoptic (SO) nuclei. The great majority of cells (85%) were neurones and most were immunoreactive to oxytocin or to vasopressin (AVP). 2. The resting [Ca2+]i of the majority (80%) of the neurones remained stable while 20% of the neurones displayed spontaneous [Ca2+]i oscillations which disappeared in low‐Ca2+ (100 nM) EGTA buffer. 3. Addition of 100 nM oxytocin increased the [Ca2+]i in both stable and oscillating cells. Two types of responses were observed: (i) a sustained response with [Ca2+]i being maintained at an elevated level and (ii) a brief response with [Ca2+]i quickly returning to a near‐resting level. Responses were reproducible, dose dependent and blocked with a specific oxytocin antagonist. 4. Removal of extracellular Ca2+ did not block the oxytocin response. In EGTA buffer, application of thapsigargin (200 nM) onto oxytocin‐sensitive cells induced an increase in [Ca2+]i and inhibited the oxytocin response. These effects were not induced by other intracellular Ca2+ mobilizers such as tBuBHQ (see Methods) or caffeine. 5. In conclusion, half of the SO cells respond to oxytocin with a rise in [Ca2+]i. The effect is mediated by oxytocin receptors and results from release of Ca2+ from thapsigargin‐sensitive stores.