Mechano-sensitivity of denervated Solus muscle of the rat L-type Ca channel mechano-sensitivity in long-term denervated Soleus muscle of the rat

Evidences showed that physical forces, as passive stretching or active contraction, may counteract various kinds of skeletal muscle atrophy due, for instance, to muscle immobilization, pathophysiology or denervation. In accord, active muscle contraction induced by functional electrical stimulation resulted helpful to reduce the muscle atrophic state in denervated man. Moreover, there are evidences that also passive mechanical stimulation of the sarcolemnic membrane may reduce the atrophic muscle state. About the mechanisms by which mechanical stimulation modulates muscle physiology and pathophysiology there is a growing list of facts that signalling pathways to the nucleus concern the cytoskeleton. The anomalous cytoskeleton organization determines leaky plasma-membrane and loss of its mechanical properties causing fragility, less stiffness and disassembling the myofibrils. Actin cytoskeleton is activated by Ca -dependent and -independent pathways and its contraction or elongation represent not only a mechanical signal to the nucleus but also a stimulus for many molecular signals that improve the muscle performance. Thus, the abnormal cytoskeleton may also affect the mechanical tension of the T-tubule membrane and consequently the functionality of the L-type Ca channel. The aim of this work was to evaluate the mechano-sensitivity of L-type Ca channels in long-term denervated Soleus muscle of the rat. Electrophysiological experiments were made in long-term (44 weeks) denervated Soleus muscle of Wistar rats. Currents were recorded in voltage-clamp by intracellular microelectrodes inserted in a single fibre. Results showed that L-type Ca channel currents were enhanced by muscle stretching.