Catechol-O-methyltransferase (COMT) was localized in the organum vasculosum of the lamina terminalis, subfornical organ, subcommissural organ and area postrema of rat brain using an indirect immunofluorescence technique. COMT immunofluorescence was apparent in neuroglia within the organum vasculosum and was most intense in the ependyma between this structure and the optic recess of the third ventricle. In both the subfornical organ and the area postrema, COMT was localized in a neuroglial network, but was noticeably absent in the ependymal layer. COMT immunofluorescence in the ependyma of the subcommissural organ was continuous with the more intense immunofluorescence of the cuboidal ependyma of the third ventricle. Each of the circumventricular organs studied, with the exception of the subcommissural organ, lies outside the blood-brain barrier. However, the unique pattern of COMT immunofluorescence in the area postrema and the subfornical organ suggests that these two structures, of all the circumventricular organs, are most likely to permit the entry of peripherally circulating catechols to the cerebrospinal fluid.
Bibliographical noteFunding Information:
This work was supported by NIH Grants NS-12311, NS-13672 and Research Scientist Development Award MH-70451 (B. K. H.).
- area postrema
- blood-brain barrier
- organum vasculosum
- subcommissural organ
- subfornical organ
- ventricular system