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The intrinsic innervation of the urinary bladder of the cat was studied with the aid of total extrinsic denervation (L7, S1, S2, S3 and the first coccygeal spinal nerves were transected and the hypogastric ganglia were extirpated on both sides); the materials were studied by electron microscopy. Several synapses could be observed between nerve processes and perikarya and between two adjacent nerve processes. The terminals could be classified into four groups according to the existence of a dense core and according to the size of the synaptic vesicles; the first group is made up of small clear vesicles; the second group of terminals contains some large granulated vesicles in addition to a few small clear vesicles; the third group of terminals contains small granulated vesicles and in the fourth type of terminals, large, 150- to 250-nm 'peptiderg' vesicles could be observed. The latter type of terminals was always observed in postsynaptic situation. Spine synapses could also be found in the ureterovesical ganglia. Several desmosome-liek attachments also could be observed between the nerve processes and perikaraya and between two nerve fibers. Up to three different types of nerve fibers have been observed on the same neuron. These morphological results suggest that the ureterovesical junction should be considered a single functional unit which plays an important role in coordinating the function of the bladder; further local circuits might exist in the urinary bladder wall.

The nerve elements in the urinary bladder of the cat were studied by electron microscopy. According to their ultrastructure, nerve cell somata can be classified into three types: the large cells with a cytoplasm rich in organelles, several processes and numerous synaptic contacts on their surface; the cytoplasm contained 80- 120-nm granulated vesicles. The second type is poor in cytoplasmic organelles and has very few processes and virtually no synaptic contacts on the soma. The third type contains numerous large 160- to 220-nm 'neurosecretory' vesicles in the cytoplasm. According to the morphology of the vesicle population, four types of nerve processes could be distinguished: Type a, with a dominant population of small (40-60 nm) agranular vesicles. These are thought to be sacral parasympathetic fibres. Type b, with small (40-60 nm) granular vesicles, which may be the noradrenergic sympathetic fibres. Type c, with 80- to 120-nm granulated vesicles, probably of local origin. Typed d, with large 160- to 220-nm 'neurosecretory' vesicles also of local origin. Different types of nerve fibres are converging on the local nerve cells. This suggests that the local circuits can play an important role in coordinating the function of the bladder. Therefore, ganglia may be considered as an elementary functional unit.