Control of LocomotionIn Vitro: I. Deafferentation

Abstract

We previously described the ability to induce adult-like, coordinated airstepping following electrical stimulation of the brainstem in the hindlimb-attached, in vitro brainstem-spinal cord preparation. These findings suggest the presence at birth of supraspinal systems capable of activating and modulating spinal locomotor mechanisms, which presumably also are present at birth. The current study employed the hindlimb-attached in vitro brainstem-spinal cord preparation from 0- to 4-day-old rats maintained in oxygenated artificial cerebrospinal fluid. After the control threshold-frequency relationship for eliciting airstepping was established, the dorsal roots to the attached limbs were severed and the procedure was repeated. No changes in electrical threshold or major differences in the elicited locomotor pattern were observed after deafferentation, although the amplitude of the electromyograms decreased. The mean frequency of alternation at threshold before deafferentation was similar to that after deafferentation. However, the maximum mean frequency induced by suprathreshold stimulation was significantly higher after deafferentation than that before deafferentation. These results suggest that (1) the supraspinal modulation of spinal locomotor mechanisms is not entirely dependent on afferent input; (2) intrinsic spinal locomotor mechanisms are present in the spinal cord at birth; and (3) afferent input may limit the maximum frequency of alternation of the limbs early in development.

Identification, Localization, and Modulation of Neural Networks for Walking in the Mudpuppy (Necturus Maculatus) Spinal Cord

“…The input through the C3 dorsal root on balance prolongs the step cycle duration, and that through the C2 dorsal root on balance shortens the cycle duration. The overall effects of dorsal rhizotomy appear to be in favor of a faster rhythm, in agreement with findings in the rat (Iakhnitsa et al, 1987;Atsuta et al, 1991;Iwahara et al, 1991). The cellular basis for this interaction remains to be resolved, but the transitional interneurons described previously (Wheatley et al, 1994) may be involved.…”

A reliable technique for the induction of locomotor-like activity in the in vitro neonatal rat spinal cord using brainstem electrical stimulation

“…Atsuta et al (1988Atsuta et al ( , 1990Atsuta et al ( , 1991b demonstrated that microelectrical stimulation of discrete sites in the in vitro neonatal rat brainstem can also evoke a locomotor-like pattern of hindlimb flexor and extensor muscle activation. However, using their method we have been able to evoke only brief episodes (e.g.…”

Reorganization of Locomotor Activity during Development in the Prenatal Rata

“…8 These features are very similar to those of the locomotor activity seen in an in vivo preparation of cats, whether it is naturally occurring or elicited by stimulating locomotor regions of the brain stem. 12 Note that the frequency, burst duration, and pattern of this locomotor‐type activity remained unchanged after transection of the dorsal roots, as shown in Figure 1Ab (see also Atsuta et al 13).…”