Effects of neuroactive substances on the activity of subcommissural organ cells in dispersed cell and explant cultures

Abstract

The subcommissural organ (SCO), an ependymal (glial) circumventricular organ, releases glycoproteins into the cerebrospinal fluid; however, the regulation of its secretory activity is largely unknown. To identify neuroactive substances that may regulate SCO activity, we investigated immunocytochemically identified bovine SCO cells by means of calcium imaging. This analysis was focused on: (1) serotonin (5HT) and substance P (SP), immunocytochemically shown to be present in axons innervating the bovine SCO; and (2) ATP, known to activate glial cells. 5HT had no effect on the intracellular calcium concentration ([Ca(2+)](i)), and its precise role remains to be clarified. SP elicited rises in [Ca(2+)](i) in approx. 30% and ATP in even 85% of the analyzed SCO cells. These effects were dose-dependent, involved NK(3) and P2Y(2) receptors linked to G protein and phospholipase C (PLC) activation, and could not be mimicked by forskolin or 8-bromo-cAMP. In 50% of the SP-sensitive cells, the increases in [Ca(2+)](i) comprised calcium release from thapsigargin-sensitive intracellular stores and an influx of extracellular calcium via protein kinase C (PKC)-induced opening of L-type voltage-gated calcium channels (VGCCs). In the remaining SP-sensitive cells, the increase in [Ca(2+)](i) was caused exclusively by influx of extracellular calcium via VGCCs of the L-type. In all ATP-sensitive cells the increase in [Ca(2+)](i) involved calcium release from thapsigargin-sensitive intracellular stores and a PKC-mediated influx of extracellular calcium via L-type VGCCs. Our data suggest that SP and ATP are involved in regulation of the activity of SCO cells.

Hyperglycemia increases SCO-spondin and Wnt5a secretion into the cerebrospinal fluid to regulate ependymal cell beating and glucose sensing

“…The presence of low-affinity glucose transporters, such as GLUT2, would allow continuous glucose uptake, which could eventually lead to rapid increases in ATP concentration, as has been previously described in tanycytes and β-pancreatic cells [2,4,25]. Additionally supporting this hypothesis, previously it was found that an increase in intracellular ATP content in SCO cells elicited rises in [Ca 2+] i in 85% of analyzed cells [24]. These effects were dose dependent and involved NK 3 and P 2 Y 2 receptors linked to G protein and PLC activation.…”

“…These effects were dose dependent and involved NK 3 and P 2 Y 2 receptors linked to G protein and PLC activation. In all ATP-sensitive cells, the increase in the [Ca 2+ ]i involves calcium release from thapsigargin-sensitive intracellular stores and PKC-mediated influx of extracellular calcium via L-type voltage-gated calcium channels (VGCCs) [ 24 ]. Thus, SCO cells would have the capacity to respond to increased glucose concentrations, increasing their apical secretion and SCO-spondin solubilization in CSF.…”

“…In vitro, it has been suggested that ATP increases SCO-spondin secretion and that 5-hydroxytryptamine (5-HT) inhibits SCO-spondin activity [ 23 ]. Additionally, in bovine SCO cells, ATP increases the [Ca 2+ ]i in approximately 85% of cells [ 24 ]. These effects are dose dependent and involve NK3 and P2Y2 receptors linked to G protein and phospholipase C activation [ 24 ].…”

“…Additionally, in bovine SCO cells, ATP increases the [Ca 2+ ]i in approximately 85% of cells [ 24 ]. These effects are dose dependent and involve NK3 and P2Y2 receptors linked to G protein and phospholipase C activation [ 24 ].…”

Spatial and single-cell transcriptomics onSSPOPTV mutant mice reveals SCO-spondin’s function in mood regulation through brain barriers

“…The copyright holder for this preprint this version posted April 12, 2024. ; https://doi.org/10.1101/2024.04.09.24305433 doi: medRxiv preprint in CSF 15,19,20 . It receives neural input, and is under neural control from multiple neural transmitter systems such as GABA, dopamine, noradrenaline and serotonin [21][22][23] , suggesting that it may be involved in stress response and mood regulation, because these neurotransmitters control basic emotions and are implicated in affective disorders 24 . Like other circumventricular organs (CVO), the SCO has axon terminals from the hypothalamus, secreting neurohormones, supporting that the SCO is functionally linked to the hypothalamus 25 .…”