Synaptic specialization of pulmonary parasympathetic ganglia: a three-dimensional study

The pulmonary parasympathetic ganglia of rhesus monkeys were studied histochemically and by using ultrastructural reconstruction. Neuropil tissue containing axosomal synapses, isolated by satellite cells surrounding the ganglion cell soma, were analyzed. Serial tri-dimensional reconstruction of axosomal specializations show that they consist of the following: (1) 'butte'-like processes of the ganglion cell surface which receive axons bilaterally at the stalk portion of the butte and have symmetric-type synaptic contacts and (2) invaginating axons which send twisted processes tunneling deep into the soma of the ganglion cell and which have characteristically asymmetric synaptic contacts and clear vesicles. The areas of synaptic contact of the pulmonary parasympathetic ganglia are thus relatively; isolated from the extracellular space.