삼차신경계에 있어서 운동신경세포의 bead-like dendrite에 대한 전자현미경적 연구

Ultrastructural study on the bead like swelling of the dendrite in the masseteric motor neuron

Recently, many researchers who investigate morphological and physiological characteristics of motor neuron with intracellular HRP injection technique found many bead like swellings on the distal portion of the dendrite. They assumed that it is caused by the collection of HRP in the course of the transport through the dendrite or by swelling for the increase surface area for the more synapse with other neuronal profiles. But, they could not found the ultrastructure and the meaning of it. So we employed the intracellular injection technique and investigated the distal dendrite of the motor neuron with electron microscope. Ultrastructurally, black HRP reaction product is located on the plasmamembrane of the mitochondria, microtubule and microfilament. The strand portion of dendrite that connect the bead-like swellings exhibited normal structure including normal arrangement of intracytoplasmic organelles. But, in the swelled portion, degenerative changes of intracytoplasmic organelles were found and many dissolved cytoplasmic areas without cytoplasmic organelles were found, the arrangement of microtubule, microfilament were irregular and in some case, resolved intracytoplasmic membrane was fund. So It is concluded that the bead like swellings of the distal dendrite of the motor neuron is degenerative portion of the dendrite which is caused by the injury of the neuron during the intracellular injection of the motor neuron.