Paraganglionic cell response to chronic imipramine and handling stress: an ultrastructural study

The ultrastructure and connectivity of monoamine-storing paraganglionic cells in the rat superior cervical ganglion were investigated following chronic treatment with imipramine (Tofranil, Ciba-Geigy) and compared with uninjected unhandled controls and saline injected animals. The study reveals a significant decrease in the number of dense core vesicles in the drug-treated group (P less than 0.001) which is regarded as a specific effect due to receptor blocking actions of imipramine. A significant reduction in the maximum diameter of the external rim and internal cores of the vesicles (P less than 0.05) in the drug-treated group is mimicked to a certain extent by saline injections, indicating a mixed effect of stress handling and specific alteration. Although the paraganglionic cell morphology is unaltered in the group comparisons, the interrelationship of the paraganglionic cells to surrounding neural processes is significantly altered in both the control versus saline and the control versus drug group comparisons (P less than 0.05). The drug- and saline-induced alterations of neural connectivity may reflect stress-induced general changes demonstrating the plasticity of the paraganglionic cell population.