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Agonist activation of cytosolic Ca2+ in subfornical organ cells projecting to the supraoptic nucleusThe subfornical organ (SFO) is sensitive to both ANG II and ACh, and local application of these agents produces dipsogenic responses and vasopressin release. The present study examined the effects of cholinergic drugs, ANG II, and increased extracellular osmolarity on dissociated, cultured cells of the SFO that were retrogradely labeled from the supraoptic nucleus. The effects were measured as changes in cytosolic calcium in fura 2-loaded cells by using a calcium imaging system. Both ACh and carbachol increased intracellular ionic calcium concentration ([Ca2+]i). However, in contrast to the effects of muscarinic receptor agonists on SFO neurons, manipulation of the extracellular osmolality produced no effects, and application of ANG II produced only moderate effects on [Ca2+]i in a few retrogradely labeled cells. The cholinergic effects on [Ca2+]i could be blocked with the muscarinic receptor antagonist atropine and with the more selective muscarinic receptor antagonists pirenzepine and 4-diphenylacetoxy-N-methylpiperdine methiodide (4-DAMP). In addition, the calcium in the extracellular fluid was required for the cholinergic-induced increase in [Ca2+]i. These findings indicate that ACh acts to induce a functional cellular response in SFO neurons through action on a muscarinic receptor, probably of the M1 subtype and that the increase of [Ca2+]i, at least initially, requires the entry of extracellular Ca2+. Also, consistent with a functional role of M1 receptors in the SFO are the results of immunohistochemical preparations demonstrating M1 muscarinic receptor-like protein present within this forebrain circumventricular organ.
Document ID
20040112493
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Johnson, R. F.
(University of Iowa Iowa City, Iowa 52242, United States)
Beltz, T. G.
Sharma, R. V.
Xu, Z.
Bhatty, R. A.
Johnson, A. K.
Date Acquired
August 21, 2013
Publication Date
May 1, 2001
Publication Information
Publication: American journal of physiology. Regulatory, integrative and comparative physiology
Volume: 280
Issue: 5
ISSN: 0363-6119
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: HL-57472
CONTRACT_GRANT: HL-14388
CONTRACT_GRANT: DK-54759
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Regulatory Physiology
Non-NASA Center

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