Effect of Guanethidine on Nerve Cells and Small Intensely Fluorescent Cells in Sympathetic Ganglia of Newborn and Adult Rats

Newborn rats were given intraperitoneal injections of 20 mg/kg body weight of guanethidine daily for 8 days. About 3 weeks later, they were killed together with their untreated litter mate controls at the age of one month. Guanethidine caused destruction of the superior cervical and coeliac ganglia, the size of which was about 10% of that of the control ganglia. The number of nerve cells in the ganglion remnants was also reduced. The mean number of the small intensely fluorescent (SIF) cells of the superior cervical ganglion increased from 479 cells/ganglion to 1427, and those of the coeliac ganglion from 198 to 1071 cells/ganglion, after guanethidine administration. The number of SIF cells increased in normally existing clusters from which grew out finger-like cell protrusions. Adult animals injected with 20 mg/kg body weight of guanethidine daily for 14 days and killed on the 15th day had superior cervical ganglia of slightly increased size. The space between the ganglion cell bodies was much increased and was infiltrated by numerous round-nucleated cells, the cytoplasm of which was non-fluorescent. The ganglion cells showed degenerative signs of varying degree, such as loss of basophilia and amine fluorescence. No increase in the number of SIF cells was observed. It is concluded that guanethidine causes a chemical sympathectomy accompanied by hyperplasia of the SIF cells in newborn rats, and severe degenerative changes with round cell infiltration in the sympathetic ganglia of adult rats.