Reversal of caffeine-induced anxiety by neurosteroid 3-alpha-hydroxy-5-alpha-pregnane-20-one in rats.

Caffeine has been shown to increase brain and plasma content of neurosteroid 3alpha-hydroxy-5alpha-pregnan-20-one (3alpha,5alpha-THP) that allosterically modulates GABA(A) receptors. The present study evaluated the role of neurosteroid 3alpha,5alpha-THP in the caffeine-induced anxiogenic-like effect using the elevated plus-maze (EPM) test in rats. Acute administration of caffeine (50 or 100mg/kg, i.p.) produced anxiogenic-like activity that was reversed by pretreatment with the neurosteroid 3alpha,5alpha-THP or progesterone, the GABA(A) agonist muscimol, or the benzodiazepine receptor agonist diazepam. On the contrary, caffeine produced higher anxiety in animals previously treated with the GABA(A) receptor antagonist, bicuculline or either of the various neurosteroid biosynthesis enzyme inhibitors viz. trilostane, finasteride or indomethacin. Furthermore, pretreatment with DHEAS, a neurosteroid that negatively modulates GABA(A) receptors also enhanced the caffeine-induced anxiety. Moreover, adrenalectomy potentiated the anxiogenic-like response of caffeine indicating the contributory role of peripheral steroidogenesis. Thus, it is speculated that neurosteroid 3alpha,5alpha-THP through positive modulation of GABA(A) receptor activity may serve as a counter-regulatory mechanism against caffeine-induced anxiety.