Functional defects in cilia are associated with various human diseases including congenital hydrocephalus. Previous studies suggested that defects in cilia not only disrupt the flow of cerebrospinal fluid (CSF) generated by motile cilia in ependyma lining the brain ventricles, but also cause increased CSF production at the choroid plexus. However, the molecular mechanisms of CSF overproduction by ciliary dysfunction remain elusive. To dissect the molecular mechanisms, choroid plexus epithelial cells (CPECs) were isolated from porcine brain. These cells expressed clusters of primary cilia on the apical surface. Deciliation of CPECs elevated the intracellular cyclic AMP (cAMP) levels and stimulated basolateralto-apical fluid transcytosis, without detrimental effects on other morphological and physiological features. The primary cilia possessed neuropeptide FF (NPFF) receptor 2. In deciliated cells, the responsiveness to NPFF was reduced at nanomolar concentrations. Furthermore, CPECs expressed NPFF precursor along with NPFFR2. An NPFFR antagonist, BIBP3226, increased the fluid transcytosis, suggesting the presence of autocrine NPFF signaling in CPECs for a tonic inhibition of fluid transcytosis. These results suggest that the clusters of primary cilia in CPECs act as a sensitive chemosensor to regulate CSF production.

Sensing extracellular milieu is a fundamental requirement of cells. To facilitate and specify sensory reception, mammalian cells develop an antenna-like structure denoted as the primary cilia. Nearly all interphase and nondividing cells in vertebrates have a single, nonmotile seemingly unspecialized cilium (called a primary cilium). In the central nervous system, astrocytes express primary cilia, but their function in astrocytes has not been examined. Recent studies have shown that primary cilia unite receptors and the machinery of signal-transduction components, such as Wnt and Hedgehog (Hh) signaling cascades. Although, Hh signaling cascades are known to be activated in various cells during development, their physiological functions in the adult nervous system, especially in glial cells, are still unknown. In this study, we reveal that glial primary cilia receive the Hh signal and regulate the survival of astrocytes under stressed conditions such as starvation. Interestingly, increased astrocyte survival was reversed by knockdown of Ift20, which is one of the main components for building primary cilia. These results collectively indicate that the activation of Hh signaling in the primary cilia plays an important role in the survival of astrocytes under stressed conditions.

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The localization of calbindin-D28K (CB) was studied immunocytochemically in laminae I and II of the dorsal horn and in spinal ganglia in the chicken, and compared with the distribution of substance P (SP) using double immunolabeling. At the light microscopic level, CB immunoreactivity was observed most intensely in the lamina II using the avidin-biotinylated peroxidase complex (ABC) and immunofluorescence methods. At the electron microscopic level using the ABC method, CB immunoreactivity was observed in the following three neuronal elements: 1) the scalloped central terminal with many dense-cored vesicles (DCVs) in the synaptic glomerulus; 2) some vesicle-containing dendrites (VCDs) inside or outside the synaptic glomerulus; and 3) some axon terminals outside the synaptic glomerulus. The CB-immunoreactive (IR) VCDs in the synaptic glomerulus often formed reciprocal synapses with the central terminal. Strong immunoreactivity was observed at the postsynaptic membrane of CB-IR elements. Double immunofluorescence and immunolabeling methods at the electron microscopic level showed that CB and SP colocalized in the scalloped central terminal with DCVs of the synaptic glomerulus. Almost all SP-IR neurons in the spinal ganglion revealed the coexistence of CB in serial sections in the chicken. In light of previous biochemical and physiological reports, our findings suggest that CB - coexisting with SP - plays an important role in the control of pain transmission through its strong Ca(2+)-buffering action in the chicken.