[Analysis of tonic activity in sympathetic ganglion neurons in the rabbit]

The patterns of tonic activity recorded with intracellular electrodes from neurons of the rabbit superior cervical ganglion whose preganglionic inputs remained intact were compared with the responses of the same neurons to single stimuli applied to preganglionic fibres. It is found that each neuron receives two preganglionic inputs, dominant and accessory. The dominant input is formed by one preganglionic fibre with a potent synaptic action on the neuron evoking a spike with high safety factor. The accessory input is formed by two or more converging preganglionic fibres that can evoke a spike only due to summation of evoked EPSPs.