Facilitation of postural limb reflexes in spinal rabbits by serotonergic agonist administration, epidural electrical stimulation, and postural training

Abstract

, and specific postural training (SPT). The factors were used either alone (SPT group) or in combination (DOIϩSPT, EESϩSPT, and DOIϩEESϩSPT groups) or not used (control group). It was found that in none of these groups did normal postural corrective movements in response to lateral tilts of the supporting platform reappear within the month of treatment. In control group, reduced irregular electromyographic (EMG) responses, either correctly or incorrectly phased in relation to tilts, were observed. By contrast, in DOIϩSPT and EESϩSPT groups, a gradual threefold increase in the proportion of correctly phased EMG responses (compared with control) was observed. The increase was smaller in DOIϩEESϩSPT and SPT groups. Dissimilarly to these long-term effects, short-term effects of DOI and EES were weak or absent. In addition, gradual development of oscillatory EMG activity in the responses to tilts, characteristic for the control group, was retarded in DOIϩSPT, EESϩSPT, DOIϩEESϩSPT, and SPT groups. Thus regular application of the three tested factors and their combinations caused progressive, long-lasting plastic changes in the isolated spinal networks, resulting in the facilitation of spinal postural reflexes and in the retardation of the development of oscillatory EMG activity. The facilitated reflexes, however, were insufficient for normal postural functions. postural corrections; spinal cord injury; (Ϯ)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride; rabbit WHEN STANDING, QUADRUPEDAL ANIMALS maintain the dorsalside-up body orientation and equilibrium due to the activity of the postural system (Deliagina et al.

A Computational Model for Epidural Electrical Stimulation of Spinal Sensorimotor Circuits

“…As a consequence, the drop of voltage across the dura primarily results from the difference between CSF and the epidural fat conductivities. Therefore, as in previous studies (McIntyre and Grill, 2002;Ladenbauer et al, 2010), we did not model the thin dura mater in our computational model.…”

“…We used established conductivity values to characterize each modeled tissue (Table 1; Ladenbauer et al, 2010), while ensuring proper continuity conditions at each boundary. A nonuniform, second-order tetrahedral mesh consisting of ϳ900,000 elements (ϳ1.2 million degrees of freedom) was generated for the discretization of the model.…”

“…Electrical parameters are reported in Table 2. The diameters of efferent axons were based on a realistic shape distribution Conductivity is scalar for isotropic tissues; the conductivity tensor is diagonal in the reference frame of the tissue (Ladenbauer et al, 2010).…”

“…In the model, the early-, medium-, and late-latency responses were proportional to the number of directly recruited (1) motor axons, (2) Group Ia fibers, and (3) both Group I and Group II fibers, respectively. The late-latency responses likely result from the recruitment of both excitatory and inhibitory interneuronal circuits that receive converging inputs from multifaceted afferents (Jankowska, 1992). Consequently, the number of recruited afferent fibers cannot predict the modulation of late-latency response.…”

“…Computational models (Struijk et al, 1992;Ladenbauer et al, 2010) and electrophysiological studies Minassian et al, 2007) suggested that EES primarily recruits proprioceptive afferent fibers in the dorsal roots and along their course in the dorsal column, but a direct action of EES onto interneurons has also been proposed Edgerton and Harkema, 2011). Here, we developed a hybrid computational model of EES that we validated comprehensively.…”