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Intracellular Calcium Increase and Somatodendritic Vasopressin Release by Vasopressin Receptor Agonists in the Rat Supraoptic Nucleus: Involvement of Multiple Intracellular Transduction Signals
Author(s) -
Sabatier N.,
Shibuya I.,
Dayanithi G.
Publication year - 2004
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/j.0953-8194.2004.01155.x
Subject(s) - vasopressin , supraoptic nucleus , agonist , endocrinology , medicine , arginine vasopressin receptor 1b , vasopressin receptor , phospholipase c , arginine vasopressin receptor 2 , chemistry , receptor , biology , antagonist
Vasopressin neurones of the supraoptic nucleus are autoregulated by vasopressin released from their soma and dendrites. Vasopressin binds to specific autoreceptors to trigger an influx of Ca 2+ , and this response involves both phospholipase C (PLC) and adenylate cyclase (AC) pathways that, in the periphery, are activated by V 1 (V 1a and V 1b )‐ and V 2 ‐type receptors. To investigate the pathways involved in the [Ca 2+ ] i response, [Ca 2+ ] i measurements were made on freshly dissociated neurones using Fura‐2 microspectrofluorimetry, and vasopressin release was measured from isolated supraoptic nuclei. The [Ca 2+ ] i increase and vasopressin release induced by the V 1a agonist were strongly inhibited by a PLC blocker, an IP 3 receptor antagonist, and a PKC blocker. An AC inhibitor did not affect the V 1a response, while PKA inhibitors significantly reduced the V 1a ‐induced [Ca 2+ ] i and release responses. The [Ca 2+ ] i increase and vasopressin release elicited by the V 2 agonist were attenuated not only by AC pathway blockers, but also by PLC inhibitors. Surprisingly, the V 1b agonist showed no [Ca 2+ ] i or vasopressin release response. In conclusion, the V 1a agonist activates both PLC and AC pathway, confirming the functional expression of a V 1a vasopressin receptor on vasopressin neurones. The V 2 agonist activation of both PLC and AC pathways could result from an action on the PLC‐linked unknown receptor, and/or the AC‐linked dual angiotensin II‐vasopressin receptor.