ISSN:
1365-2826
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
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 Ca2+, and this response involves both phospholipase C (PLC) and adenylate cyclase (AC) pathways that, in the periphery, are activated by V1 (V1a and V1b)- and V2-type receptors. To investigate the pathways involved in the [Ca2+]i response, [Ca2+]i measurements were made on freshly dissociated neurones using Fura-2 microspectrofluorimetry, and vasopressin release was measured from isolated supraoptic nuclei. The [Ca2+]i increase and vasopressin release induced by the V1a agonist were strongly inhibited by a PLC blocker, an IP3 receptor antagonist, and a PKC blocker. An AC inhibitor did not affect the V1a response, while PKA inhibitors significantly reduced the V1a-induced [Ca2+]i and release responses. The [Ca2+]i increase and vasopressin release elicited by the V2 agonist were attenuated not only by AC pathway blockers, but also by PLC inhibitors. Surprisingly, the V1b agonist showed no [Ca2+]i or vasopressin release response. In conclusion, the V1a agonist activates both PLC and AC pathway, confirming the functional expression of a V1a vasopressin receptor on vasopressin neurones. The V2 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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.0953-8194.2004.01155.x
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