Morphological and electrophysiological properties of pelvic ganglion cells in the rat

Intracellular recording and dye injection were used to study the morphological and electrophysiological properties of rat pelvic ganglion cells. The dye-injected cells measured on the average 37 micron by 22.5 micron and had a mean number of 1.5 primary processes (axon and dendrites). The cells received unmyelinated preganglionic inputs from either the pelvic (parasympathetic) or the hypogastric (sympathetic) nerves, but no cells received inputs from both nerves. The number of synaptic inputs to each cell varied between 1 and 5 with a mean of 2. Each cell had at least one large amplitude suprathreshold EPSP which always initiated an action potential. These properties, namely, morphological simplicity, small number of inputs, security of synaptic transmission and lack of convergence between sympathetic and parasympathetic inputs, suggest that the capacity for synaptic modulation and integration in this ganglion is minimal. Such a structure should therefore relay preganglionic information to target organs with little or no alteration.