Capsaicin, the pungent extract of red pepper, has neurotoxic effects when injected into neonates and great interest has been focused on this subject. Capsaicin causes diminution of calcitonin gene-related peptide (CGRP) in the dorsal horn of spinal cord and in the peripheral nervous system. However, it is reported that
capsaicin has no effects on the enteric nervous system. This experiment was performed to investigate the effect of capsaicin on CGRP containing neurons and on
the peripheral axons in the enteric nervous system. Capsaicin 50mg/kg was injected in 2nd and 4th day of life to Sprague-Dawley rats, and 10 weeks and 6 months later, the whole mount preparation of the intestine was prepared and stained immunohistochemically with anti-CGRP antiserum. Electron-micrographical samples were also prepared. The results obtained are as follows. 1) The distribution pattern of CGRP immunoreactive cells was different depending upon the site of the intestine, that is, the ileum showed the most complicated and dense pattern. 2) After capsaicin treatment, CGRP immunoreactive cells showed decreased or no reactivity in the 6 month group, while no changes were observed in the 10 week group. 3) In electron-micrographical findings, enteric neurons showed changes similar to the changes of the primary sensory neurons. Enlargement and destruction of mitochodria and increment of dense bodies were observed, while enlargement of peripheral nerve ending with cell organelles lysis was common.