Distribution of dendrites from longissimus lumborum motoneurons stained intracellularly with biocytin in adult cats.

The three-dimensional distribution of dendrites from motoneurons innervating longissimus lumborum (Long Motoneurons) in the L4 spinal segment was examined in the adult cat using intracellular staining techniques. Long Motoneurons were electrophysiologically identified, stained with injection of biocytin and reconstructed from serial histological sections. Somas of Long Motoneurons were mainly located in the lateral-ventral area of the ventral horn. The dendritic distribution followed an orderly pattern in all motoneurons examined. Long Motoneurons showed a multi-directional distribution of dendrites, and the dendritic distribution pattern varied depending on the motoneuron. All studied motoneurons distributed dendrites from the spine into the white matter. The most significant morphological characteristic of the Long Motoneurons was the variation in their dendritic distribution. No relationship was observed between the effects of peripheral afferent inputs from the hindlimb and morphological characteristics of motoneurons.