Neuroactive steroid-serotonergic interaction: responses to an intravenous L-tryptophan challenge in women with premenstrual syndrome

Objective: To evaluate the circulating concentrations of the neuroactive st eroids in response to an i.v. L-tryptophan (L-TP) challenge across the mens trual cycle in women with premenstrual syndrome (PMS) and in controls. Method: An i.v. L-TP challenge was administered eight times during 1 month to five women with prospectively documented PMS and five age- and body mass -matched controls. Progesterone, allopregnanolone pregnenolone and 3 alpha -5 alpha -tetrahydrocorticosterone were assessed 15 and 0 min before. and a t 30, 60 and 90 min after the challenge, across the menstrual cycle. Results: In response to L-TP challenge, only allopregnanolone concentration s were significantly increased across the cycle and this increase was of a greater magnitude in women with PMS. Pregnenolone and 3 alpha -5 alpha -tet rahydrocorticosterone concentrations were not affected in women with PMS or controls after L-TP challenge. Conclusions: The data provide evidence for possible interaction between the serotonergic system and the neuroactive steroid, allopregnanolone. Women w ith PMS demonstrated a more significant increase in allopregnanolone concen trations in response to L-TP challenge, which could be due to an initial lo w basal serotonergic tone in the luteal phase in the PMS group.