Endocannabinoid system in the adult rat circumventricular areas: An immunohistochemical study

Abstract

Endocannabinoids (ECs) are important neuromodulators involved in a plethora of physiological processes such as modulation of synaptic transmission, neuroprotection, immune function, and neurodevelopment, among others. However, still lacking is a detailed study on the presence of this system in the circumventricular areas, brain structures controlling the interaction between cerebrospinal fluid and brain parenchyma. The aim of this work was to provide the anatomical basis supporting a functional role of ECs in the activity of circumventricular areas. To this end, an immunohistochemical study of the EC system in rat brain was performed. Receptors and synthesizing and degrading enzymes for ECs were widely distributed in rat ependyma and subependyma, marginal glia, and circumventricular organs (CVOs) such as the choroid plexus, subfornical organ, subcommissural organ, median eminence, and area postrema. These zones constitute barrier systems between the brain parenchyma and the ventricular or subarachnoid cerebrospinal fluid (CSF) and between the extracellular hemal milieu of CVOs and the brain parenchyma or the CSF. By immunohistochemistry and real-time polymerase chain reaction we found DAGLalpha, DAGLbeta, NAPE-PLD, MAGL, and FAAH in the ependyma. These finding suggest that the ependyma can release and clear ECs from the ventricular CSF. Subependymal astrocytes and tanycytes displayed DAGLalpha immunoreactivity but parenchymal astrocytes did not express EC-synthesizing enzymes, thus establishing a sharp distinction between these two astrocyte populations. CB1 was located in fibers innervating discrete subventricular zones such as the neurogenic striatal subventricular zone and the fourth ventricle. CB1 fibers also innervated some CVOs.

Astrocytic TRPV1 ion channels detect blood‐borne signals in the sensory circumventricular organs of adult mouse brains

“…It is also shown that depolarization-induced release of glutamate from astrocytes is modulated by endocannabinoid system including TRPV1 (Bari et al, 2011). A preferential expression of endocannabinoid synthesizing and degrading enzymes is shown to be present at astrocytes and tanicytes in the sensory CVOs (Su arez et al, 2010). The information on an increase of the Na þ level in body fluids sensed by Nax in glial cells is transmitted into neurons of the SFO by lactate (Shimizu et al, 2007).…”

From Phytocannabinoids to Cannabinoid Receptors and Endocannabinoids: Pleiotropic Physiological and Pathological Roles Through Complex Pharmacology

“…Astrocytes are able to synthesize endocannabinoids (820) and participate in endocannabinoid turnover in the brain (56). Biosynthetic enzymes as well as FAAH and MAGL are expressed in astrocytes (827,861). A recent study genetically dissected the cellular anatomy of MAGLmediated 2-AG metabolism in the brain and showed that neurons and astrocytes coordinately regulate 2-AG levels and CB1-mediated synaptic plasticity and behavior, and that astrocytic MAGL converts 2-AG to neuroinflammatory prostaglandins (882).…”

Cannabinoid receptor type 1 expression during postnatal development of the rat retina

“…The anti-DAGLa reacted with a single band at 120 kDa as described by the manufacturer and other authors (Suarez et al, 2008;Gao et al, 2010;Suarez et al, 2010).…”