Pinealocytes contacting the cerebrospinal fluid of the suprapineal recess in the Mongolian gerbil (Meriones unguiculatus).

The pineal system of the Mongolian gerbil (Meriones unguiculatus) was investigated by light and electron microscopy, special attention being paid to the sites of contact with the ventricular system. The results reveal that the pineal system of this species has a specific topographical relationship to the suprapineal recess of the third ventricle. The dorsal side of the proximal part of the pineal system forms the floor and the caudal wall of this recess. Here, a consistent and relatively large area lacks an ependymal lining, enabling pinealocytes to come into direct contact with the cerebrospinal fluid (CSF). This area is assumed to be the morphological correlate of a close functional interrelationship between the pineal tissue and the CSF.