Central and peripheral influences on retention of postural asymmetry in rats.

Abstract

Four studies were conducted to delineate potential neural processes involved in retention of a peripherally induced postural asymmetry. In the first experiment, dorsal and ventral spinal root section following varying intervals of stimulation successfully abolished peripherally induced hindlimb asymmetry. Experiment 2 revealed that 50 min of ventral root stimulation, in the absence of central connection, was not effective in producing asymmetry persistence. In an attempt to more closely delineate the time parameters involved in peripherally induced asymmetry retention, Experiment 3 was conducted. Asymmetry was found to consistently outlast a spinal transection if 40 min of stimulation was given. Finally, possible modulatory higher brain center influences on the retention processes were demonstrated in Experiment 4. Asymmetry persistence was consistently observed in animals that received 10, 20, 30, 40, or 50 min of hindlimb stimulation if 50 min were allowed to elapse between the onset of stimulation and spinal section. These results, when coupled with the findings of earlier studies, suggest an active involvement of spinal reflex centers in the fixation process. In addition, these studies indicate that the manner in which reflex activity is altered is not crucial as long as underlying time parameters are adhered to. Finally, the present studies demonstrate that higher center influences can modulate retention of a postural asymmetry in a complex manner.

Behavioral and Anatomical Characterization of the Bilateral Sciatic Nerve Chronic Constriction (bCCI) Injury: Correlation of Anatomic Changes and Responses to Cold Stimuli

“…Reciprocal flexion and extension of opposing limbs can occur in response to natural stimulation [41]. Furthermore, tonically asymmetric postures can be produced by repetitive cutaneous stimulation [42]. Thus, in unilateral CCI rats, extensor tone of the contralateral, normal limb can be enhanced, interfering with withdrawal of the normal limb and reducing weight transfer to the injured side necessary for lifting responses of the intact hindpaw.…”

Temporal parameters involved in retention of reflex alterations in spinal rats.

“…Differences in temporal aspects of retention were found when data obtained from the spinal animals in the present study were compared with data collected from intact rats that received stimulation. Previous studies (Steinmetz et al, 1982) have indicated that intact animals require 40 min of hindlimb stimulation to consistently retain peripherally induced flexion. The present study involving spinal animals, however, demonstrates that only 30 min of stimulation is necessary to consistently obtain the same effect.…”

“…Recently, we began a neurophysiological analysis of retention of postural asymmetry in rats (Steinmetz, Cervenka, Dobson, Romano, & Patterson, 1982;Steinmetz, Cervenka, Robinson, Romano, & Patterson, 1981). With the use of Requests for reprints should be sent to Michael M. Patterson, College of Osteopathic Medicine, Ohio University, Athens, Ohio 45701. electrolytic lesions placed in the anterior lobe of the cerebellum, asymmetry was found to consistently outlast a spinal transection if 45 min were allowed to elapse between brain lesion and cord section.…”

Bilateral Chronic Constriction of the Sciatic Nerve: A Model of Long-term Cold Hyperalgesia

“…30 Furthermore, tonically asymmetric postures can be produced by repetitive cutaneous stimulation 37 and by partial and asymmetric deafferentation of spinal reflex circuits by a supraspinal lesion. 3 These and related phenomena (eg, the crossed extension reflex) have been studied in relation to motor control of postural stability and activities such as alternating limb movements during locomotion.…”