Intracranial distribution of the sympathetic system in mice: DiI tracing and immunocytochemical labeling

The intracranial distribution of the cephalic branches of the superior cerv ical ganglion (scg) was studied in mice using indocarbocyanine dye (DiI) an terograde tracing. Two main branches were traced from the scg. The first br anch joined the nerve of the pterygoid canal (the vidian nerve), npc, from which several intracranial sympathetic branches passed to the branches of t he trigeminal nerve (tgn), abducent nerve (abn), trochlear nerve (trn), and oculomotor nerve (ocn). Most of the second branch joined the abn, from whi ch sympathetic fibers dispersed in the distal region of the trigeminal gang lion (tgg) to form a plexus close to the ganglion's branches. Branches from this plexus joined the branches of the tgn, trn, and ocn. Several minor br anches arising from the second branch of the scg were also observed. One fo rmed a sympathetic plexus around the internal carotid artery (ica); a secon d formed a sympathetic plexus in the proximal region of tgg, close to its r oot; and a third branch coursed laterally to reach the ear by passing along the greater petrosal nerve (gpn). All of the intracranial trajectories tra ced from scg were found to be catecholaminergic, and likely sympathetic, us ing tyrosine hydroxylase (TH) immunocytochemistry. Anat Rec 263: 99-111, 20 01. (C) 2001 Wiley-Liss, Inc.