Insight into the temporial evolution of spontaneous Ca2+ signals generated by ventral neurons during spinal cord maturation in vitro

Similar heterogeneity was observed following the application of the Ca2+ stores depletory, thapsigargin that induced either block (62% of neurons) or persistence (38%) of oscillations. The oscillatory activity was not dependent on ryanodine-sensitive stores. Abstract 4 Thus, despite the stereotyped properties of oscillations (origin, periodicity, etc), these events could be generated with the contribution of multiple Ca2+ sources. A second issue relevant in identifying oscillating neurons was to monitor the patterns of expression of Ca2+ binding proteins and of Cl- co-transporters, KCC2 and NKCC1. I observed a strong dependence of the expression profile of the Ca2+-binding protein calbindin on developmental maturation. This was not an universal phenomenon, in fact, other Ca2+ binding proteins, such as calretinin and parvalbumin, did not follow the same pattern. I did not detect differences in the expression pattern of NKCC1, between 1 and 2 weeks of in vitro growth, conversely KCC2-ir was more located to neuronal processes along with development. Recent results show that H2O2 is an endogenous donor of reactive oxygen species present in the CNS in ?M concentrations (Lei et al., 1998). In the postnatal spinal cord, H2O2 has been recently indicated as a soluble, Ca2+ dependent mediator, capable of modulating synaptic plasticity under physiological and pathological conditions (Takahashi et al., 2007). In this study, physiological concentrations of H2O2 increased intracellular Ca2+ only in oscillating neurons without changing the oscillation period. The fact that oscillating neurons were the only responsive cells to a low H2O2 dose suggested that these spinal interneurons could be critical transducers of the modulatory action