ABSTRACT
Calbindin D-28K (CALB) is one of the calcium-binding proteins which is assumed to be buffering, transport of Ca2+, and regulation of various enzyme systems. In the spinal cord, a subpopulation of calbindin-immunoreactive neurons located in the ventral portion of lamina VII, medial to the motoneuron column, has recently been proposed to be Renshaw cells (RCs), that mediate recurrent inhibition of spinal alpha-motoneurons, based on the anatomical location. In this study, we have performed to investigate the correlation between RCs containing high levels of CALB and motoneurons in the ventral horn of lumbar spinal cord of the ataxic pogo mice, that characterized by a failures of interlimb coordination, and prolonged excessive tone of hindlimb extensor muscles. We have shown that CALB immunoreactive RCs was significantly decreased in the ventral horn of lumbar spinal cord of the ataxic pogo mice (p.0.05), when compared with the control mice. Whereas, CALB immunoreactivity expression levels were no difference in the dorsal horn. Furthermore, CALB protein was significantly decreased in the lumbar spinal cord of the ataxic pogo mice (p.0.01). However, there were no difference in the cervical and thoracic spinal cord of the between control and pogo mice. These results suggest that motoneurons of ventral horn of the lumbar spinal cord might be more excited state, results in the decreased CALB immunoreactive RCs have not mediated a motoneuron excitability, in the atxic mice, pogo.
Subject(s)
Animals , Mice , S100 Calcium Binding Protein G , Calcium-Binding Proteins , Hindlimb , Horns , Muscles , Neurons , Spinal CordABSTRACT
The pogo mouse is a new ataxic mutant derived from a Korean wild mouse. The pogo mutation is inherited as an autosomal recessive trait on chromosome 8. Mutations in gene coding for the alpha(1A)subunit of voltagegated P/Q-type Ca(2+) channel have been shown to cause phenotypes in humans and mice, i.e., tottering, leaner, rolling mouse mouse Nagoya. Using immunohistochemistry, the expression of the alpha(1A)subunit of voltage-gated P/Q-type Ca(2+) channel was examined in pogo mice cerebellum including deep cerebellar nuclei (DCN). We observed alpha(1A)immunoreactivity in the cerebellar cortex (Purkinje cell and granule cell) and DCN of ataxic pogo mice and heterozygote control mice. There was no difference in cerebellar cortical alpha(1A)immunoreactivity between ataxic pogo mice and heterozygous littermate controls (pogo/+). However, we observed alpha(1A)immunoreactivity in the Purkinje cells of control and ataxic pogo mice cerebellum and DCN. We found a significant difference between pogo and heterozygous controls in terms of alpha(1A)immunoreactivities in the DCN. alpha(1A)immunoreactivity in this nucleus in pogo was much higher than in heterozygous littermate controls. No significant differences were observed in the interposed nucleus between pogo and heterozygous controls, but we found that the alpha(1A)subunits were clearer and more abundant in the lateral and medial regions of pogo than in control mice in these regions, where only weak immunoreactivity was observed. This elevated expression of the alpha(1A)subunit in deep cerebellar neurons of pogo might be a compensation for the altered function of P/Q type calcium channel and be related with the induction of the ataxic phenotype in pogo mice.
