Ultrastructural localization of monoamines in nerve fibers of the pineal gland in golden hamsters

Morphometric analysis of the synaptic ribbons and nerve vesicles of the cat pineal gland after electrical stimulation of the superior cervical ganglia

The nerve vesicles and synaptic ribbons were quantified in the cat pineal gland after electrical stimulation of the pineal sympathetic nerve fibers. It has been shown that the bilateral electrical stimulation of the preganglionic fibers innervating the superior cervical ganglia (SCG) markedly reduces the number of dense cores of small dark vesicles (SDV) and, on the other hand, modifies the number and shape of the large dark vesicles (LDV). An increase in the number of the synaptic ribbons after stimulation of the SCG supports the hypothesis that the numerical reduction of dense cores of nerve vesicles in the cat pineal gland influences the level of synaptic ribbon formation.

Synaptic junctions between the adrenergic axon varicosity and the pinealocyte in the rat

Intercellular relationships of sympathetic nerve fibers and cells in pineal glands of Long-Evans rats and yellow-bellied country rats (Rattus losea Swinhoe) were studied with conventional electron microscopy. Typical synapses were found between adrenergic axon varicosities and pinealocytes. The synaptic cleft was 20-30 nm thick and contained granular or filamentous material of moderate electron density. Some small granulated vesicles attached to, or fused with, the presynaptic axolemma, a feature suggesting an exocytotic release of the vesicle content. The occurrence of membranous cisternae or tubules in the synaptic nerve ending may connote the phenomenon of synaptic vesicle recycling. Beneath the postsynaptic pinealocyte plasmalemma there was a dense plaque corresponding to the postsynaptic density of neurons. Possible origins and functional significance of the synapse-making nerve fibers are also discussed.