Ca 2+ sparks and Ca 2+ glows in superior cervical ganglion neurons

Aim: Ca 2+ release from the endoplasmic reticulum (ER) is an integral component of neuronal Ca 2+ signaling. The present study is to investigate properties of local Ca 2+ release events in superior cervical ganglion (SCG) neurons. Methods: Primary cultured SCG neurons were prepared from neonatal rats (P3–P7). Low concentration of caffeine was used to induce Ca 2+ release from the ER Ca 2+ store, and intracellular Ca 2+ was recorded by high-resolution line scan confocal imaging and the Ca 2+ indicator Fluo-4. Results: Two populations of local Ca 2+ release events with distinct temporal characteristics were evoked by 1.5 mmol/L caffeine near the surface membrane in the soma and the neurites of SCG neurons. Brief events similar to classic Ca 2+ sparks lasted a few hundreds of milliseconds, whereas longlasting events displayed duration up to tens of seconds. Typical somatic and neurite sparks were of 0.3- and 0.52-fold increase in local Fluo-4 fluorescence, respectively. Typical Ca 2+ glows were brighter (∆F/F0 approximately 0.6), but were highly confined in space. The half maximum of full duration of neurite sparks was much longer than those in the soma (685 vs 381 ms). Conclusion: Co-existence of Ca 2+ sparks and Ca 2+ glows in SCG neurons indicates distinctive local regulation of Ca 2+ release kinetics. The local Ca 2+ signals of variable, site-specific