Immunohistochemical demonstration of S-100 protein and GFA protein in interstitial cells of rat pineal gland.

Ependym und Circumventriculäre Organe

The photoreceptor cells are transducers which absorb incident photons and transmit a proportional signal to other cells. More complex retinal functions such as the discrimination of colors and the detection of contrast and movement are accomplished by networks of many cells. This chapter is a critical historical review of attempts to establish the spatial relationships of the structural, functional, and chemical units in the retina which correspond to such networks.

The Morphological Organization of the Vertebrate Retina

Synaptic ribbons (SR) of the mammalian pineal gland are functionally enigmatic. In the present study it is shown that in male guinea-pigs kept under a lighting regimen of 12 hrs illumination (7.00–19.00) and 12 hrs darkness (19.00–7.00) the SR of pinealocytes vary about 25-fold in number over a period of 24 hrs. An increase is found between 15.00 and 6.00 and a decrease between 6.00 and 15.00. Analysis of the intracellular localization and the topographical relationships indicate that SR lie near the cell membrane of pinealocytes throughout the 24 hr period and that they are related to adjacent pinealocytes. A working hypothesis put forward implies that SR represent cell organelles involved in intercellular communication and that it is their function to either enhance the secretory activity of the pineal gland or to establish circuits within the gland between adjacent pinealocytes, similar to neuronal circuits.

Synaptic ribbons of a mammalian pineal gland circadian changes

In the rabbit pineal gland two types of postganglionic nerve endings were found which are characterized by the presence of small dense-core vesicles or small clear vesicles. Pharmacological and cytochemical experiments showed then to be noradrenergic and cholinergic, respectively. Both types were often present in the same nerve bundle, occasionally in close opposition. Intrapineal neurons were only rarely observed. They showed cholinergic synapses on their perikaryon and dendrites as well as noradrenergic axo-dendritic close contacts. Bilateral extirpation of the superior cervical ganglia revealed the postganglionic sympathetic origin of the pineal noradrenergic nerve fibres. Moreover, it appeared that these ganglia are hardly, if at all, involved in the pathway of pineal cholinergic innervation. The results obtained from lesions of both facial nerves, taken together with the results reported in the literature, led to the conclusion that the postganglionic cholinergic nerve fibers in the pineal are of parasympathetic origin. A model for the sympathetic and parasympathetic pineal innervation is proposed.

Structure and innervation of the pineal gland of the rabbit, Oryctolagus cuniculus (L.). II. An electron microscopic investigation of the pinealocytes.

Antti U. Arstila

Papers

Electron Microscopic Studies on the Structure and Histochemistry of the Pineal Gland of the Rat