Limb immobilization alters functional electrophysiological parameters of sciatic nerve

Abstract

Immobilization, used in clinical practice to treat traumatologic problems, causes changes in muscle, but it is not known whether changes also occur in nerves. We investigated the effects of immobilization on excitability and compound action potential (CAP) and the ultrastructure of the rat sciatic nerve. Fourteen days after immobilization of the right leg of adult male Wistar rats (n=34), animals were killed and the right sciatic nerve was dissected and mounted in a moist chamber. Nerves were stimulated at a baseline frequency of 0.2 Hz and tested for 2 min at 20, 50, and 100 Hz. Immobilization altered nerve excitability. Rheobase and chronaxy changed from 3.13±0.05 V and 52.31±1.95 µs (control group, n=13) to 2.84±0.06 V and 59.71±2.79 µs (immobilized group, n=15), respectively. Immobilization altered the amplitude of CAP waves and decreased the conduction velocity of the first CAP wave (from 93.63±7.49 to 79.14±5.59 m/s) but not of the second wave. Transmission electron microscopy showed fragmentation of the myelin sheath of the sciatic nerve of immobilized limbs and degeneration of the axon. In conclusion, we demonstrated that long-lasting leg immobilization can induce alterations in nerve function.

Hepatic glycogen levels in female rats submitted to aquatic therapy after muscle disuse

“…A previous study about acute intermittent jumping exercise in rats showed an increase in glucose levels and decreased hepatic glycogen levels (Romijn et al, 1993), corroborating with the data obtained in this study. Blood glucose control is essential to the functions of glucose dependent tissues, maintained through consumption of carbohydrates, glycogenolysis and gluconeogenesis (Alves et al, 2013). Exercise increases the oxidation of muscle glycogen (Rogatto et al, 2004), and the reduction of liver glycogen evidenced in this study may be related to higher consumption of muscle glycogen during exercise or as a replacement strategy for muscle glycogen.…”

“…These data are consistent with previous studies, showing that a short period of disuse by immobilization generates weight reduction (Carvalho et al, 2014;Santos Júnior et al, 2010), reduction in muscle length (Carvalho et al, 2014) and contractile capacity (Santos Júnior et al, 2015). It is known that disuse by immobilization promotes several morphological and physiological changes (Alves et al, 2013) and it acts directly in the muscle tone loss, leading to muscle atrophy (Santos Júnior et al, 2010). Two weeks of immobilization can cause loss of myofibrils and decrease of the size of muscle fibers (Ploug et al, 1995), changes in the morphology of the fibers and muscle mechanics .…”

“…Several biochemical, metabolic and structural changes are found in muscle disuse related to immobilization (Alves et al, 2013;Volpi et al, 2008). Among them is muscle atrophy, a process that causes loss of strength, gradual decreasing of the activities performed by the patient and metabolism changes (Appell, 1990).…”

Análise da função pulmonar e estrutura micromecânica após 14 dias de restrição de movimento em ratas

“…Both situations may limit the patients' full abilities such as their locomotion and some activities of daily life 1,2 . Small periods of movement restriction, even short-term ones, can lead to several damages to the immobilized region 3 , including disorders in various body segments and organic systems, such as circulatory impairments 1 , ligament alterations 4 , increase of the connective issue 5 , edema 6 , articular rigidity 4 , muscle hypertrophy and atrophy 7 and reduction in bone mineral density 3,8 . In general, depending on the immobilized region and the restraint time, the respiratory system can be compromised.…”

“…These damages in the mechanical structure of the diaphragm and the consequent reduction of diaphragmatic movement and thoracic excursion can cause an increase in the mechanical resistance and a decrease of the pulmonary ventilation, leading to atelectasies and pneumonias 9 . Several studies approach the impact of immobilization on the locomotor system [1][2][3]6,7 ; however, little is known about the respiratory system regarding the effects of devices that constrain the torso movement. In this context, the present study examined the impact that the restriction of abdominal movement from an experimental model containing multiple motor limitations can promote on the structure and function of the respiratory system and whether they are reversible with recruitment maneuver.…”