A rise in the intracellular Ca2+ concentration of isolated rat supraoptic cells in response to oxytocin.
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.
Lambert
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Laboratoire de Neurobiologie Endocrinologique, URA 1197-CNRS, Université Montpellier II, France.
Dayanithi
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Moos
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Richard
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D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001127:Arginine Vasopressin / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D005260:Female; D016257:Fura-2; D006873:Hydroquinones / Q000494:pharmacology; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008297:Male; D010121:Oxytocin / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D013194:Staining and Labeling; D013495:Supraoptic Nucleus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D014668:Vasotocin / Q000031:analogs & derivatives / Q000494:pharmacology
D000975:Antioxidants; D006873:Hydroquinones; D013729:Terpenes; D001127:Arginine Vasopressin; C076093:vasotocin, (beta-mercapto-beta,beta-cyclopentamethylenepropionic acid)-O-methyl-Tyr(2)-Thr(4)-Orn(8)-Tyr(9)-NH2; C019359:2,5-di-tert-butylhydroquinone; D002110:Caffeine; D010121:Oxytocin; D019284:Thapsigargin; D000252:Calcium-Transporting ATPases; D002118:Calcium; D016257:Fura-2; D014668:Vasotocin