| Abstract: | The ultrastructure of parasympathetic neurons in the otic ganglia of the rabbit is described with the object of providing a basis for comparisons of parasympathetic with sympathetic nerve cells. The neuronal cytoplasm contains Nissl substance, mitochondria, dense bodies, agranular Golgi membranes, neurofilaments (60 to 100 Å in diameter) and microtubules having diameters about 200 Å and filled with irregularly dense material. Granulated vesicles (about 900 Å in diameter) consisting of a limiting membrane and enclosing a dense spherical droplet of about 500 Å diameter are also present in the cytoplasm and processes of these neurons and in presynaptic terminals, thus disproving the hypothesis put forward by some authors that the presence of granulated vesicles indicates a sympathetic nervous pathway. Long, tubular bodies with a dense central core are described which are possibly peculiar to parasympathetic neurons. The nuclear membrane is double, porous and sometimes exhibits localized, deep invaginations of its surface. Junctional complexes are described between apposing membranes of neurons and satellite cells which are morphologically similar to zonulae adhaerentes. Small gaps exist in the cytoplasmic sheath surrounding the neurons. Over these areas only a basement membrane separates the nerve cell from the connective tissue space and the significance of this finding is discussed. |
