Systemic administration of murine monoclonal
acetylcholinesterase antibodies to rats has been shown to cause selective degeneration of sympathetic preganglionic neurons. In the present study rats were subjected to a single i.v. injection of these
acetylcholinesterase antibodies, or to normal
IgG or saline for control.
Exophthalmos, piloerection and eyelid-drooping (ptosis) were observed within 1 h after administration of the
antibodies. Rats were killed at different time-points after antibody administration, and the adrenal glands were analysed by means of indirect immunohistochemistry and in situ hybridization histochemistry. As soon as 3 h after the antibody treatment, a marked increase in the number of chromaffin cells expressing
mRNA encoding, respectively,
enkephalin,
calcitonin gene-related peptide,
galanin,
neurotensin and
substance P was seen. At 12 h the
peptide mRNA levels were still elevated and there was a concomitant increase in the number of
peptide-immunoreactive cells. All
peptide levels remained high for at least 48 h; however, 77 days after the antibody treatment only
enkephalin-immunoreactive cells could be encountered. A disappearance of
acetylcholinesterase- and
enkephalin-immunoreactive cells could be encountered. A disappearance of
acetylcholinesterase- and
enkephalin-positive fibers was already seen 3 h after the antibody treatment, and after 24 h no fibers were encountered. In contrast, up until 48 h there was no apparent change in the number or intensity of immunofluorescent fibers expressing
calcitonin gene-related peptide,
galanin,
neurotensin or
substance P. However, 77 days after the antibody treatment the number of
calcitonin gene-related peptide- and
substance P-immunoreactive fibers was increased as compared to controls. In addition, reappearance of
acetylcholinesterase- and
enkephalin-immunoreactive fibers was seen 77 days after antibody administration, although their number was still low as compared to controls. Double-labeling immunohistochemistry revealed that the chromaffin cells expressing
peptides after the antibody treatment preferentially were
adrenaline storing cells (
noradrenaline-negative). The majority of these cells expressed only one
peptide. Both surgical transection of the splanchnic nerve as well as treatment with
acetylcholine receptor antagonists mimicked the effects seen after the
acetylcholinesterase-antibody treatment, although changes were less pronounced. The present results show that interruption of splanchnic transmission induces fast, marked, and selective increases in
peptide expression in rat adrenal chromaffin cells.