The subcommissural organ expresses D2, D3, D4, and D5 dopamine receptors

Abstract

Dopamine receptors have been found in certain populations of non-neuronal cells in the brain, viz., discrete areas of ciliated ependyma and the ependymal cells of the choroid plexus. We have studied the presence of both tyrosine-hydroxylase-immunoreactive nerve fibers and dopamine receptors in the subcommissural organ (SCO), an ependymal brain gland that is located in the roof of the third ventricle and that secretes, into the cerebrospinal fluid, glycoproteins that aggregate to form Reissner's fiber (RF). Antibodies against D2, D3, D4, and D5 dopamine receptors were used in immunoblots of bovine striatum, fresh SCO, and organ-cultured SCO, and in immunocytochemistry of the bovine, rat, and mouse SCO. Only a few tyrosine-hydroxylase fibers appeared to reach the SCO. However, virtually all the secretory ependymal and hypendymal cells of the SCO immunoreacted with antibodies against D2, D4, and D5 receptors, with the last-mentioned rendering the strongest reaction, especially at the ventricular cell pole of the secretory ependymocytes, suggesting that dopamine might reach the SCO via the cerebrospinal fluid. The antibodies against the four subtypes of receptors revealed corresponding bands in immunoblots of striatum and fresh SCO. Although the cultured SCO displayed dopamine receptors, dopamine had no apparent effect on the expression of the SCO-spondin gene/protein or on the release of RF-glycoproteins (SCO-spondin included) by SCO explants, suggesting that dopamine affects the function(s) of the SCO differently from the secretion of RF-glycoproteins.

Transcriptome signature of the adult mouse choroid plexus

“…Other studies, using autoradiographic techniques with selective ligands, failed to detect the mu and delta opioid receptors in rat CP brain [25,26], probably due to the lower sensitivity of the methodologies used. The present study also confirmed the presence of other neurotransmitter receptors previously described in the CP [27], such as the dopamine receptors. Again, this emphasizes an active role of the CP as a potential site for modulating response to neurotransmitters, which should be further investigated in the context of mood disorders.…”

AmphiD1/β, a dopamine D1/β-adrenergic receptor from the amphioxus Branchiostoma floridae: evolutionary aspects of the catecholaminergic system during development

“…Furthermore, the amphioxus infundibular organ, considered homologous to the vertebrate subcommisural organ (Olsson et al 1994), expresses the AmphiD1/β receptor. Such expression is consistent with the finding of D1-like receptors in the vertebrate subcommisural organ (Tomé et al 2004), and we can then suggest an involvement of the AmphiD1/β receptor in the modulation of chemosensory pathways.…”

Circumventricular Organs

“…A few catecholaminergic fibers also reach the SCO (Tomé et al, 2004). Dopamine receptors (D2, D3, D4 and D5) are present on SCO ependyocytes, but probably respond to CSF-borne dopamine rather than that released from nerve fibers in the SCO (Tomé et al, 2004). The SCO exhibits a dense capillary network running beneath the ependymocytes (Duvernoy and Koritke, 1969).…”

“…Serotonergic fibers from the raphé provide some of this neural input (Møllgård et al, 1978;Bouchard, 1979). A few catecholaminergic fibers also reach the SCO (Tomé et al, 2004). Dopamine receptors (D2, D3, D4 and D5) are present on SCO ependyocytes, but probably respond to CSF-borne dopamine rather than that released from nerve fibers in the SCO (Tomé et al, 2004).…”