5-Hydroxytryptamine-immunoreactive neurons and nerve fibers in the superior cervical ganglion of the rat.

Indirect immunofluorescence method was used to localize 5-hydroxytryptamine-immunoreactive structures in the superior cervical ganglion of adult rats. In the ganglia of normal rats, 5-hydroxytryptamine immunoreactivity was localized in the small intensely fluorescent cells, but not in principal nerve cells. In the superior cervical ganglion of rats, pretreated with nialamide, a monoamine oxidase inhibitor, 150 mg/kg i.p., and the 5-hydroxytryptamine precursor, L-tryptophan, 45 mg/kg i.p., a large number of 5-hydroxytryptamine-immunoreactive principal nerve cells and small intensely fluorescent cells were detected. The immunoreactive principal nerve cells had long processes, and 5-hydroxytryptamine-immunoreactive nerve fibers were observed traversing the ganglion. In ganglia of rats pretreated with colchicine, occasional 5-hydroxytryptamine-immunoreactive principal nerve cells and several small intensely fluorescent cells were detected. Ligation of the main postganglionic nerve trunks of the superior cervical ganglion of normal rats resulted in the appearance of several 5-hydroxytryptamine-immunoreactive principal nerve cells and nerve fibers in the ganglion. To study whether the 5-hydroxytryptamine immunoreactivity in the superior cervical ganglion represented uptake or synthesis of 5-hydroxytryptamine, rats were injected with a specific 5-hydroxytryptamine uptake inhibitor, fluoxetine, 10 mg/kg i.p. twice a day for 5 days, and then they were treated with nialamide and L-tryptophan, as described above. In the superior cervical ganglion of fluoxetine-treated rats, a few 5-hydroxytryptamine-immunoreactive principal nerve and small intensely fluorescent cells, as well as some nerve fibers, were detected.(ABSTRACT TRUNCATED AT 250 WORDS)