Pharmacological topics of bone metabolism: the physiological function of the sympathetic nervous system in modulating bone resorption.

The vertebrate skeleton is richly innervated with adrenergic and peptidergic nerve terminals, and these play important roles in bone remodeling. Recent studies have generally shown that increased sympathetic nervous activity causes bone loss via an increase in bone resorption and a decrease in bone formation. Increased bone resorption is based on the stimulation of both osteoclast formation and osteoclast activity. These effects are associated with beta(2)-adrenergic activity toward both osteoblastic and osteoclastic cells. Such findings indicate that beta-blockers may be effective against osteoporosis, in which case there is increased sympathetic activity. This review summarizes evidence obtained both in vitro and in vivo implicating sympathetic neuron action in bone resorption.