The relation of postsynaptic geometry to the number of presynaptic axons that innervate autonomic ganglion cells.

We have studied the shape of rabbit ciliary ganglion cells in relation to the number of axons that innervate each neuron. Adult ganglion cells receive synapses from one to seven different preganglionic axons. Some neurons lack dendrites altogether, whereas others have complex arborizations of up to eight primary dendrites. The neurons that receive all of their synaptic contacts from a single preganglionic axon usually have no dendrites; on the other hand, multiply innervated ganglion cells receive synapses from a number of different axons that increases in proportion to the number of primary dendrites that they possess. A possible explanation of these results is that individual ciliary ganglion cells comprise a number of separate spatial domains, each of which is largely constrained to receive innervation from a single preganglionic axon.