Structure and innervation of the pineal gland of the rabbit,Oryctolagus cuniculus (L.)

Summary A light microscopic investigation of the rabbit pineal gland with the aid of silver-stained sections gave the following results. In the gland a medulla and a cortex can be distinguished, the medulla containing so-called light and dark pinealocytes, the cortex only light ones. Autonomic nerve fibres reach the pineal organ by two routes: (1) via the perivascular spaces of pineal blood vessels and (2) via two distinct nerve bundles, the nervi conarii. Bilateral superior cervical ganglionectomy revealed that these pinealo-petal nerve fibres are mainly orthosympathetic postganglionic. Intramural pineal neurones with synaptic-like structures on their cell bodies and dendrites point to the presence of a parasympathetic innervation next to the orthosympathetic one. Direct afferent or efferent neural connections with the brain appeared to be absent. Acknowledgements. The author wishes to thank Professor Dr. J. Ariëns Kappers for encouragement and help, Mr. H. K. Koerten for his technical assistance and Miss A. M. Feddema for typing the manuscipt.