Cerebrospinal fluid from amyotrophic lateral sclerosis has no effect on intracellular free calcium in cultured cortical neurons

The data from the literature regarding the presence of a neurotoxic factor in amyotrophic lateral sclerosis (ALS) plasma or cerebrospinal fluid (CSF) remain controversial. As a new approach to this question, we have studied the effect of CSF from ALS patients on the temporal dynamics of the intracellular free calcium concentration ([Ca²⁺]_i) of murine cortical neurons in cultures using Fura-2 fluorescence videomicroscopy and single-cell imaging. CSF from seven ALS patients and controls was added at dilutions up to 20% to cortical neuronal cultures. The in vitro inhibition of CSF on [³H]kainic acid binding showed that the CSF did not contain any substances other than glutamate itself in larger amounts. At the concentrations used, the CSF did not have any effect on [Ca²⁺]_i or on the neuronal responsiveness as defined by the ability of the cells to respond with a transient increase in [Ca²⁺]_i to depolarization induced by KCl. The disturbance of the intracellular calcium homeostasis is one of the key mechanisms of action of excitotoxic compounds mediating delayed neuronal cell death by stimulation of glutamate receptor subtypes. In this study, CSF from ALS patients did not induce immediate rises in [Ca²⁺]_i or disturbances of the intracellular calcium homeostasis when measured over a period of 2 h.