ON PROPERTIES OF SYNAPTOID TERMINATIONS OF UNMYELINATED FIBERS IN PULVINAR CORPORIS PINEALIS IN BOMBINA VARIEGATA (L)

The synaptoid terminations of granulated unmyelinated fibers in the neuropile of the pulvinar corporis pinealis in Bombina variegata have been studied by light and electron microscopy. Vesicles with the structural properties of synaptic vesicles in the synaptoid terminations in the pulvinar corporis pinealis as well as identically shaped vesicles in the plexiform regions of the pineal organ and in unmyelinated fibers terminating between ependymal cells of the subcommissural organ can be stained selectively by aid of the zinciodide-osmium method. On the other hand granules with electron dense core in the pulvinar do not react. Size and number of the granulated vesicles in the axons of the pulvinar cannot be influenced by injection of reserpine or the benzoquinolizine derivative Ro 4-1284. The possible mechanism of discharge of secretory material and the probability of the presence of a cholinergic mechanism are discussed. © 1969 Springer-Verlag.