Physiological response of bovine subcommissural organ to endothelin 1 and bradykinin

Abstract

The circumventricular organs (CVOs) regulate certain vegetative functions. Receptors for bradykinin (BDK) and endothelin (ET) have been found in some CVOs. The subcommissural organ (SCO) is a CVO expressing BDK-B2 receptors and secreting Reissner's fiber (RF) glycoproteins into the cerebrospinal fluid. This investigation was designed to search for ET receptors in the bovine SCO and, if found, to study the functional properties of this ET receptor and the BDK-B2 receptor. Cryostat sections exposed to (125)I ET1 showed dense labeling of secretory SCO cells, whereas the adjacent ciliated ependyma was devoid of radiolabel. The binding of (125)I ET1 was abolished by antagonists of ETA and ETB receptors. The intracellular calcium concentration ([Ca(2+)](i)) was measured in individual SCO cells prior to and after exposure to ET1, BDK, or RF glycoproteins. ET1 (100 nM) or BDK (100 nM) caused an increase in [Ca(2+)](i) in 48% or 53% of the analyzed SCO-cells, respectively. RF glycoproteins had no effect on [Ca(2+)](i) in SCO cells. ET and BDK evoked two types of calcium responses: prolonged and short responses. Prolonged responses included those with a constant slow decline of [Ca(2+)](i), biphasic responses, and responses with a plateau phase at the peak level of [Ca(2+)](i). ET1-treated SCO explants contained a reduced amount of intracytoplasmic AFRU (antiserum to RF glycoproteins)-immunoreactive material compared with sham-treated control explants. Our data suggest that ET1 and BDK regulate [Ca(2+)](i) in bovine SCO cells, and that the changes in [Ca(2+)](i) influence the secretory activity of these cells.

Understanding How the Subcommissural Organ and Other Periventricular Secretory Structures Contribute via the Cerebrospinal Fluid to Neurogenesis

“…This include serotonergic ( Bouchaud, 1979 ; Jiménez et al, 2001 ), gabaergic and catecholaminergic ( Balaban et al, 1994 ; Tomé et al, 2004 ) inputs ( Figure 3D ). SCO-cells also express receptors for angiotensin II ( Ghiani et al, 1988 ), endothelin 1 and bradykinin ( Schöniger et al, 2009 ). The serotonergic input exerts and inhibitory control on the expression and release of SCO-spondin ( Richter et al, 2004 ).…”