Low-dose brain estrogen prevents menopausal syndrome while maintaining the diversity of the gut microbiomes in estrogen-deficient rats

We evaluated the effects of intracerebroventricular administration(ICV) of brain estrogen and progesterone on menopausal symptoms and their effects on the secretion of follicle-stimulating hormone(FSH) and luteinizing hormone(LH) in estrogen-deficient rats. Three weeks after ovariectomy(OVX) or Sham-operation, OVX rats were given ICV infusions of either 17β-estradiol(4 μg/day; ICV-E), progesterone(0.8 μg/day; ICV-P), or vehicle(control) for 4 weeks. OVX rats in the positive-control group were orally provided 150 μg 17β-estradiol/kg bw/day. Sham rats had ICV vehicle infusion(normal-control). Serum 17β-estradiol levels of ICV-E and ICV-P groups were higher than the control group but much lower than the normal- and positive-control groups. Tail skin temperature was higher in the control group than the other groups. Serum FSH and LH levels were much higher in the control group than positive- and normal-control groups, but ICV-E and ICV-P lowered the levels similar to the normal-control group. ICV-E and ICV-P ...