Caffeine inhibits exercise-induced increase in tryptophan hydroxylase expression in dorsal and median raphe of Sprague-Dawley rats

Neurosci Lett. 2001 Jul 27;308(1):25-8. doi: 10.1016/s0304-3940(01)01980-2.


Effect of caffeine on the expression of tryptophan hydroxylase (TPH), rate limiting enzyme of serotonin synthesis, in dorsal and median raphe was investigated via immunohistochemistry. In exercise groups, Sprague-Dawley rats were put on treadmill running for 30 min per day for 6 consecutive days. On the seventh day, animals of control-with-caffeine group were injected subcutaneously with 4 mg/kg caffeine, while control-without-caffeine group were injected with 0.9% NaCl, sacrificed 2 h later. Exercise-with-caffeine group and exercise-without-caffeine group were injected with caffeine and NaCl, respectively; all-out time was determined 1 h after injection, and then sacrificed. Caffeine increased all-out time in exercised rats, and inhibited the exercise-induced elevation in TPH expression. The suppressive effect of caffeine on TPH expression in exercised rats can be suggested as one possible ergogenic mechanism of caffeine.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Caffeine / pharmacology*
  • Central Nervous System Stimulants / pharmacology*
  • Exercise Test
  • Immunohistochemistry
  • Male
  • Neurons / cytology
  • Neurons / drug effects*
  • Neurons / enzymology
  • Physical Conditioning, Animal
  • Physical Exertion / drug effects*
  • Physical Exertion / physiology
  • Raphe Nuclei / cytology
  • Raphe Nuclei / drug effects*
  • Raphe Nuclei / enzymology
  • Rats
  • Rats, Sprague-Dawley
  • Serotonin / biosynthesis*
  • Tryptophan Hydroxylase / drug effects*
  • Tryptophan Hydroxylase / metabolism


  • Central Nervous System Stimulants
  • Serotonin
  • Caffeine
  • Tryptophan Hydroxylase