Exp Neurobiol 1:21-27, 1992

Immunohistochemical and electronmicroscopical study of the myenteric plexus of the rat after capsaicin treatment

Kyu Seok Lee, Ho Yoon, Jong Eun Lee, You Sun Kang, Kyung Ah Park, Won Taek Lee, Tai Sun Shin

Department of Anatomy, Yonsei University College of Medicine

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 substance P (SP) in the dorsal horn of spinal cord and in the peripheral nervous system; 90% of unmyelinated nerve fibers are destructed by capsaicin. This experiment was performed to investigate the effect of capsaicin on substance P containing neurons and on the peripheral axons in the enteric nervous system.

Capsaicin 50 mg/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-SP antiserum. Electron-micrographical samples were prepared. The results obtained are as follows.

1) The distribution patterns of SP immunoreactive cells was different depending upon the site of the intestine, that is, ileum showed most complicated and dense pattern.
2) After capsaicin treatment, SP immunoreactive cells showed decreased or no activity 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 mitochondria and increment od dense bodies were observed, while enlargement of peripheral nerve endings with cell organelles lysis was common.

Key words: capsaicin, myenteric plexus, substance P, peripheral nerve axon