ABSTRACT
BACKGROUND: Propranolol is a nonselective competitive adrenergic β-receptor blocker capable of suppressing sympathetic nerve excitation. Postmenstrual osteoporosis may be associated with the changes of sympathetic nerve activity.OBJECTIVE: To observe the effect of propranolol on tibial morphology in ovariectomized rats, and compare it with that of estrogen medication.DESIGN: Completely randomized design and controlled experiment.SETTING: End ocrinology Department, General Hospital of Beijing Military Area Command of Chinese PLA.MATERIALS: This experiment was conducted at the animal laboratory of the Institute of Basic Theory Research of Traditional Chinese Medicine between March 2002 and April 2003. Forty female unmated SD rats aged 6 months were included and randomized into 4 groups with 10 rats in each group: sham-operation group, estrogen medication group, propranolol treatment group, and placebo group.METHODS: ① Rats in estrogen group, propranolol treatment group and placebo group were anesthetized before the abdomen was opened and bilateral ovaries were excised. Rats in sham-operation group had their abdominal cavity opened and a piece of ovary surrounding fattytissue excised before closing the abdomen. ② Estrogen medication group: Rats were given hypodermic injection of grain oil dissolved 17 β-estradiol at a dose of 20 μg/(kg·d). Propranolol treatment group: Propranolol was used for gastric infusion at a dose of 18 mg/(kg·d). Placebo group and sham-op-eration group: The same volume of grain oil and/or distilled water was used instead of hypodermic injection or gastric infusion. Two treatment groups were given the same intervention as placebo group and sham-operation group during treatment; medication was carried out from postoperative week 1 for altogether 12 weeks. ③ Leica Qwin imaging analysis system was used for morphological measurement of bone tissues so as to calculate the volume percentage, active-surface formation percentage, mineralization rate, and formation rate of bone trabecula. ④ t-test was used for comparing the differences.MAIN OUTCOME MEASURES: Comparison of rat tibial morphological parameters between groups.RESULTS: Forty rats were divided into four groups with 10 rats in each and all entered the result analysis. ① Left tibial active-surface formation percentage and mineralization rate of bone trabecula: They were obviously lower in sham-operation group and estrogen group than in placebo group (P ＜ 0.01), but obviously higher in propranolol treatment group than placebo group (P ＜ 0.05). ② Formation rate of left tibial trabecula: It was obviously higher in propranolol treatment group than in placebo group (P ＜ 0.05). ③ The volume percentage of left tibial bone trabecula: It was obviously higher in sham-operation group and propranolol treat ment group than in placebo group (P ＜ 0.01), but obviously lower in pro pranolol treatment group than in sham-operation group and estrogen group (P ＜ 0.01). CONCLUSION: Propranolol can increase bone mass, reduce bone loss, and promote bone formation in osteoporotic rats following ovariectomy, thus displaying obvious preventive and therapeutic effects on osteoperesis in rats.
ABSTRACT
The purpose of the present study was to investigate the mechanism of the effect of estrogen on the production of acetylcholine in the brain and to study the regulatory role of acupuncture of Zusanli acupoint in acetylcholine production in the brain of ovariectomized rats. Experimental female Wistar rats were divided into three groups: intact group (INT), ovariectomized group (OVX), and ovariectomy and acupuncture group (OVX+AC). Radioimmunoassay (RIA) was used to measure the estrogen content in plasma. The mRNA expression of choline-acetyltransferase (ChAT) and glyceraldehyde phosphate dehydrogenase (GAPDH) in the brain of rats was measured by the RT-PCR technique and was tested by the method of agarose gel electrophoresis. The ChAT mRNA positive neurons in the hippocampus were observed by using in situ hybridization and the results were processed with a computerized image analysis system. The results are as follows. Compared with the control animals, the plasma estrogen level was significantly lowered in ovariectomized animals. However, the plasma estrogen level was higher in the OVX+AC group than that of the OVX group. The ChAT mRNA expression level of OVX+AC group was higher than that of the OVX group. The area and integral optical density of the ChAT mRNA positive neurons in the hippocampus increased more obviously in OVX+AC group than in the OVX group. The experimental results observed indicate that the expression of ChAT gene in the brain is possibly related to the estrogen level in the body. The expression of ChAT gene in the brain of the ovarietomized rat can be regulated by acupuncture of Zusanli acupoint and it may be one of the mechanisms that acupuncture increases acetylcholine content in the brain.