Topography of functional subpopulations of neurons in the superior cervical ganglion of the rat.

This study describes the distribution patterns of neurons in the rat SCG that project to a number of spatially separated and functionally different target tissues. Fluorescent dyes were used to label retrogradely neurons that project to the pineal gland, iris, nictitating membrane, Müller's smooth muscle of the eyelid, submaxillary gland, thyroid gland, tongue, buccal mucosa, and skin in several areas of head and neck. The numbers of neurons in the various subpopulations were quantified and, in several instances, postganglionic nerve transection was used to correlate the topography of subpopulations with the exit site/s of their projections from the ganglion. Individual neurons were found to have very limited projection fields and contralateral innervation of bilateral targets appeared to be minimal. Neurons with specific functions or projection fields were not highly localised within the SCG, but there was a general rostrocaudal organisation of neurons with respect to the position of their targets along the rostrocaudal axis of the body and this was correlated with the exist sites of the neurons from the ganglion.