Innervation of small intensely fluorescent cells in frog sympathetic ganglia

Autonomic ganglia have a population of small intensely fluorescent (SIF) cells with unknown function. We have investigated the afferent innervation of SIF cells in bullfrog sympathetic ganglia using intracellular recordings and light microscopy of stained preganglionic axon terminals. Contrary to previous knowledge, bullfrog SIF cells do indeed receive functional synaptic input and this innervation is provided solely by the C-type preganglionic nerve fibers.