IMMUNOLOGICALLY INDUCED SYMPATHECTOMY OF PREGANGLIONIC NERVES BY ANTIBODIES AGAINST ACETYLCHOLINESTERASE - INCREASED LEVELS OF PEPTIDES ANDTHEIR MESSENGER-RNAS IN RAT ADRENAL CHROMAFFIN CELLS

Systemic administration of murine monoclonal acetylcholinesterase anti bodies to rats has been shown to cause selective degeneration of sympa thetic 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 administratio n of the antibodies. Rats were killed at different time-points after a ntibody administration, and the adrenal glands were analysed by means of indirect immunohistochemistry and in situ hybridization histochemis try. 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 an d substance P was seen. At 12 h the peptide mRNA levels were still ele vated and there was a concomitant increase in the number of peptide-im munoreactive cells. All peptide levels remained high for at least 48 h ; however, 77 days after the antibody treatment only enkephalin-immuno reactive cells could be encountered. A disappearance of acetylcholines terase- and enkephalin-positive fibers was already seen 3 h after the antibody treatment, and after 24 h no fibers were encountered. In cont rast, up until 48 h there was no apparent change in the number or inte nsity of immunofluorescent fibers expressing calcitonin gene-related p eptide, galanin, neurotensin or substance P. However, 77 days after th e antibody treatment the number of calcitonin gene-related peptide- an d substance P-immunoreactive fibers was increased as compared to contr ols. 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-l abeling immunohistochemistry revealed that the chromaffin cells expres sing peptides after the antibody treatment preferentially were adrenal ine storing cells (noradrenaline-negative). The majority of these cell s expressed only one peptide. Both surgical transection of the splanch nic nerve as well as treatment with acetylcholine receptor antagonists mimicked the effects seen after the acetylchol-inesterase-antibody tr eatment, although changes were less pronounced. The present results sh ow that interruption of splanchnic transmission induces fast, marked, and selective increases in peptide expression in rat adrenal chromaffi n cells.