Calcium-containing endosomes at oculomotor terminals in animal models of ALS

ALTERED calcium homeostasis has been demonstrated in human spinal cord moto r axon terminals of ALS patients, in spinal motor neurons of mutant SOD tra nsgenic mice and following injection of ALS immunoglobulins. In all three p aradigms oculomotor neurons are relatively spared. To explore mechanisms of selective resistance, we applied similar calcium localization techniques t o terminals of oculomotor neurons in the two animal models. In both cases l arge vacuoles, which connect with the extracellular space, accumulated the majority of intracellular calcium, while terminals of vulnerable neurons (e .g. innervating interosseus muscle), which possess no such vacuoles, displa yed evenly distributed calcium. These relatively unique membrane enveloped structures may permit neurons to control their cytoplasmic Ca2+ concentrati on and contribute to selective resistance. NeuroReport 10:2539-2545 (C) 199 9 Lippincott Williams & Wilkins.