INTERNEURONAL SYNAPSES IN THE LOCAL GANGLIA OF THE CAT URINARY-BLADDER

The interneuronal synapses of the urinary bladder in the cat were studied by EM. The great majority of the fibers containing vesicles are found within the ganglia occurring in the trigonum area. Morphologically differentiated synaptic contacts were observed on the surface of the local neurons and between the different nerve processes. The presynaptic terminals can be divided into 3 types based on a combination of synaptic vesicles. Type I terminals, presumably cholinergic synaptic terminals, contain only small clear vesicles of 40-50 nm in diameter. Type II terminals, presumably adrenergic terminals, are characterized by small granulated vesicles of 40-60 nm in diameter. Type III terminals, probably of local origin, contain a variable number of large granulated vesicles of 80-140 nm in diameter. Occasionally, a single nerve fiber contacted several (2 or 4) other nerve processes forming a typical synapse. In other cases, on 1 nerve cell soma or on other nerve processes there are 2 or 3 different-type nerve terminals establishing synapses. Convergence and divergence may occur in the local ganglia and cholinergic and adrenergic synaptic terminals may modulate the ganglionic activity. A local circuit also can play an important role in coordinating the function of the bladder.