A new measure of hindlimb stepping ability in neonatally spinalized rats.

One of the most widely used animal models for assessing recovery of locomotor functioning is the spinal rat. Although true differences in locomotor abilities of these animals are exhibited during treadmill testing, current measurement techniques often fail to detect them. The HiJK (Hillyer-Joynes Kinematics) scale was developed in an effort to distinguish more effectively between groups of spinal rats. Scale items were compiled after extensive review of the literature concerning development and analysis of rat locomotion and a thorough examination of the current tools. Treadmill tests for 137 Sprague-Dawley rats were taped and scored. The structure of the scale was tested with principle components and factor analysis, in which six of the eight items accounted for 59% of the variance, while all eight accounted for 78%. Validity tests demonstrate that HiJK is measuring locomotor performance accurately and powerfully. First, the HiJK scale correlates highly (>.8) with the widely used BBB scale and second, as shown with ANOVA, can distinguish between different groups of spinal rats. Reliability of the scale was also analyzed. Cronbach's alpha was shown to be .91, indicating considerable internal consistency. Additionally, inter-rater and intra-rater reliabilities were substantial, with correlations for most items reaching above .80. We believe that the HiJK scale will help researchers verify existing experimental differences, advance the field of spinal cord research, and, hopefully, lead to discovery of methods to enhance recovery of function.

The neonatal injury-induced spinal learning deficit in adult rats: central mechanisms.

Previous research has shown that small injuries early in development can alter adult pain reactivity and processing of stimuli presented to the side of injury. However, the mechanisms involved and extent of altered adult spinal function following neonatal injury remain unclear. The present experiments were designed to 1) determine whether the effects of neonatal injury affect processing contralateral to the injury and 2) evaluate the role of cells expressing the NK1 receptor, shown to be involved in central sensitization in adults, in the negative effects of neonatal injury. The present findings indicate that the effects of neonatal injury are primarily isolated to the injured hind limb and do not result in a bilateral alteration in adult spinal function. In addition, the effects of neonatal injury appear to be partially dependent on cells expressing the NK1 receptor as ablating these cells at the time of injury or in adulthood results in attenuation of the neonatal injury-induced spinal learning deficit.