The purpose of this study is to clarify the effects of 17beta-estradiol and the Japanese herbal medicine Keishi-bukuryo-gan on the release and synthesis of calcitonin gene-related peptide (CGRP) in ovariectomized (OVX) rats. The effect of ovariectomy on the release or synthesis was evaluated by measuring CGRP concentration in plasma after capsaicin (1.0 mg/kg, i.p.) injection or by measuring CGRP concentration and its mRNA expression in dorsal root ganglia in OVX rats. Ovariectomy attenuated the capsaicin-evoked increase in plasma concentration of CGRP, which was restored by treatment with 17beta-estradiol (0.010 mg/kg, s.c.) or Keishi-bukuryo-gan (1000 mg/kg, p.o.) for 7 days after ovariectomy. However, no significant differences were observed in the CGRP concentration and the mRNA expression of dorsal root ganglia by treating the rats with ovariectomy, 17 beta-estradiol, and Keishi-bukuryo-gan. These results suggest not only that estrogen deficiency attenuates CGRP release but also that 17beta-estradiol or Keishi-bukuryo-gan normalizes the attenuated release process.