Abstract
Electrical stimulation of myelinated afferent fibers of the superior laryngeal nerve (SLN) facilitates calcitonin secretion from the thyroid gland in anesthetized rats. In this study, we aimed to quantify the electrical SLN stimulation-induced systemic calcitonin release in conscious rats and to then clarify effects of chronic SLN stimulation on bone mineral density (BMD) in a rat ovariectomized disease model of osteoporosis. Cuff electrodes were implanted bilaterally on SLNs and after two weeks recovery were stimulated (0.5 ms, 90 microampere) repetitively at 40 Hz for 8 min. Immunoreactive calcitonin release was initially measured and quantified in systemic venous blood plasma samples from conscious healthy rats. For chronic SLN stimulation, stimuli were applied intermittently for 3–4 weeks, starting at five weeks after ovariectomy (OVX). After the end of the stimulation period, BMD of the femur and tibia was measured. SLN stimulation increased plasma immunoreactive calcitonin concentration by 13.3 ± 17.3 pg/mL (mean ± SD). BMD in proximal metaphysis of tibia (p = 0.0324) and in distal metaphysis of femur (p = 0.0510) in chronically SLN-stimulated rats was 4–5% higher than that in sham rats. Our findings demonstrate chronic electrical stimulation of the SLNs produced enhanced calcitonin release from the thyroid gland and partially improved bone loss in OVX rats.
Highlights
Osteoporosis is characterized by reduced bone mineral density (BMD) and changes in bone morphometry, which increases the risk of fracture
superior laryngeal nerve (SLN) stimulation using these to the continuous SLN stimulation, electrical pulses at 90 μA of intensity were applied intermittently parameters did not cause any adverse behavior in conscious rats
We examined the effect of SLN stimulation on systemic immunoreactive CT (iCT) and sampled systemic venous blood
Summary
Osteoporosis is characterized by reduced bone mineral density (BMD) and changes in bone morphometry, which increases the risk of fracture. Osteoporosis is one of the most common health problems of the elderly, estimated to affect 200 million women worldwide. Drug therapy is mainly used for the treatment of osteoporosis, but the current pharmacotherapy options have various limitations such as side effects (e.g., nausea or pain with bisphosphonates) and treatment compliance [1,2]. Calcitonin (CT), a peptide hormone secreted from the thyroid gland, suppresses osteoclast activity, preventing bone loss [3]. Exogenous CT has been widely used as a bone resorption inhibitor for the treatment of osteoporosis. CT products have a short half-life and produce large
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