Brain-pineal nervous connections in the rat: an ultrastructure study following habenular lesion.

The neural connections of the pineal gland with the central nervous system (CNS) were studied in rats by stereotaxic lesioning followed by electron microscopic determination of nerve terminal degeneration. Electrolytic lesions were placed in the right medial habenular nucleus and after 3--14 days survival, the animals were prepared for electron microscopy. Control animals contained nerve terminals with 40--60 nm dense core vesicles located in the perivascular space of the pineal and in the intraparenchymal area. In the lesioned animals many electron-lucent degenerating nerve terminals could be observed intermingled with normal nerve terminals in the perivascular spaces. These degenerating terminals were often swollen and contained one side of the terminal. Both normal and degenerating nerve terminals were also observed in the parenchyma between the pinealocytes. The present findings indicate that nerve fibers from the habenular area actually terminate in the rat pineal gland.