B2-adrenceptors are present in skeletal muscle and help to orchestrate muscle cell growth in response to agonist binding. Clenbuterol is a B2-adrenoceptor agonist which has been shown to induce muscle hypertrophy in animals. The authors investigated the potential of clenbuterol in preserving muscle form and function after sciatic nerve injury in a rat model. The sciatic nerve in one hind limb of each rate was divided and immediately repaired. The contralateral hind limb in each rat served as an internal control. Clenbuterol was administered by gastric lavage daily for six weeks with periodic interruptions to avoid drug desensitization. Clenbuterol reduced the loss of wet weight, total protein, and muscle fiber cross sectional area in denervated hind limb muscles. Slow-twitch muscle showed greater sensitivity to the drug than fast-twitch muscle.
This study suggests that B2-agonist drugs may have a role as an adjunct to the surgical management of peripheral nerve injuries. The authors appropriately mention the potential for adverse side effects in other organ systems. The changes in the innervated control hind limbs in this study tended to be small. Furthermore, no increase was measured in the wet weight of cardiac muscle. Other studies, however, using higher doses of clenbuterol in rats have demonstrated potentially adverse changes in cardiac tissue (Maltin et al, Muscle and Nerve 15: 919-925, 1992; Suzuki et al, Acta Physiol Scand 161: 317-326, 1997).