MITOCHONDRIAL DENSITY OF VENTRAL HORN NEURONS IN THE RAT SPINAL-CORD

Mitochondrial density in neurons of the dorsolateral region of the ven tral horn at the L5 spinal cord segment in rats was examined using ele ctron microscopy. The gamma motoneurons had a higher density of mitoch ondria (25.1+/-4.2%, n=19) in the cytoplasm compared to the alpha moto neurons which had a mitochondrial density of 19.4+/-4.5% (n=38). An in verse relationship between cell body size and mitochondrial density wa s found for alpha (n=38) and alpha plus gamma (n=57), but not for gamm a (n=19), motoneuron populations. The higher densities of mitochondria in the smaller neurons correspond well with their metabolic propertie s since the smaller neurons have the highest oxidative enzyme activiti es.