An implantable device for stimulation of denervated muscles in rats

The purposes of the present study were (1) to develop an implantable device capable of being pre-programmed to generate a protocol of chronic contractions in denervated hind-limb muscles of rats, and (2) to verify the design by implanting the stimulators for five weeks in rats to identify a protocol of stimulation that maintains muscle mass and maximum force in stimulated-denervated extensor digitorum longus (EDL) muscles. This implantable stimulator system did not hinder animal movement or hygiene, and enabled the animals to be housed in regular animal facilities, since neither external equipment nor an externally generated magnetic field was required. The pre-programmable microcontroller allows detailed basic research into the cellular and tissue response to different stimulation protocols. The micropower design of the battery powered device enabled chronic stimulation of denervated EDL muscles for the five weeks of this initial study. Stimulation protocols of 9-11 V pulse amplitude, 0.4 ms bipolar pulse width, 100 Hz, 20 pulses per contraction, and 100 or 300 contractions generated per day maintained muscle mass and maximum force in denervated EDL muscles of rats at values near control values for innervated muscles.