Module 2: Figure cADPR action in neurons
cADPR potentiates Ca2+ transients induced by action potentials in sympathetic neurons.
When sympathetic neurons are stimulated for 10 ms at 20 Hz, there is a distinct transient made up of Ca2+ entering through voltage-operated channels (VOCs) together with release of Ca2+ from internal stores through a process of Ca2+-induced Ca2+ release (CICR). The latter component is quite variable and depends upon the sensitivity of the ryanodine receptors (RYRs). When the neurons are perfused with cyclic ADP-ribose (cADPR), there is a large increase in the amplitude of the transient (compare responses a and b in panel A). Note how the increase developed slowly over the recording period. There was no augmentation when the neurons were perfused with control solution (panel B). Reproduced from Neuron, Vol. 12, Hua, S.-Y., Tokimasa, T., Takasawa, S., Furuya, S., Nohmi, M., Okamoto, H. and Kuba, K., Cyclic ADP-ribose modulates Ca2+ release channels for activation by physiological Ca2+ entry in bullfrog sympathetic neurons, pp. 1073–1709. Copyright (1994), with permission from Elsevier; see Hua et al. 1994.