Caffeine-induced increases in the brain and plasma concentrations of neuroactive steroids in the rat

Pharmacol Biochem Behav. 2000 May;66(1):39-45. doi: 10.1016/s0091-3057(00)00237-9.


The effects of caffeine, a naturally occurring stimulant, on the brain and plasma concentrations of neuroactive steroids were examined in the rat. A single intraperitoneal injection of caffeine induced dose- and time-dependent increases in the concentrations of pregnenolone, progesterone, and 3alpha-hydroxy-5alpha-pregnan-20-one (allopregnanolone) in the cerebral cortex. The increases were significant at a caffeine dose of 25 mg/kg and greatest (+188, +388, and +71%, respectively) at a dose of 100 mg/kg in rats killed 30 min after caffeine administration. Caffeine also increased the plasma concentrations of pregnenolone and progesterone with a dose-response relation similar to that observed in the brain, whereas the caffeine-induced increase in the plasma concentration of allopregnanolone was maximal at a dose of 50 mg/kg. Caffeine increased the plasma concentration of corticosterone, but it had no effect on the brain or plasma concentrations of 3alpha, 21-dihydroxy-5alpha-pregnan-20-one and dehydroepiandrosterone. Moreover, the brain and plasma concentrations of pregnenolone, progesterone, and allopregnanolone were not affected by caffeine in adrenalectomized-orchiectomized rats. These results suggest that neuroactive steroids may modulate the stimulant and anxiogenic effects of caffeine.

MeSH terms

  • Animals
  • Caffeine / pharmacology*
  • Cerebral Cortex / chemistry
  • Cerebral Cortex / drug effects*
  • Dose-Response Relationship, Drug
  • Hypothalamo-Hypophyseal System / drug effects
  • Hypothalamo-Hypophyseal System / physiology
  • Male
  • Pituitary-Adrenal System / drug effects
  • Pituitary-Adrenal System / physiology
  • Pregnanolone / metabolism*
  • Pregnenolone / metabolism*
  • Progesterone / metabolism*
  • Rats
  • Rats, Sprague-Dawley


  • Caffeine
  • Progesterone
  • Pregnenolone
  • Pregnanolone