Effect of knockout of α(2)δ-1 on action potentials in mouse sensory neurons

Gene deletion of the voltage-gated calcium channel auxiliary subunit α(2)δ-1 has been shown previously to have a cardiovascular phenotype, and a reduction in mechano- and cold sensitivity, coupled with delayed development of neuropathic allodynia. We have also previously shown that dorsal root ganglion (DRG) neuron calcium channel currents were significantly reduced in α(2)δ-1 knockout mice. To extend our findings in these sensory neurons, we have examined here the properties of action potentials (APs) in DRG neurons from α(2)δ-1 knockout mice in comparison to their wild-type (WT) littermates, in order to dissect how the calcium channels that are affected by α(2)δ-1 knockout are involved in setting the duration of individual APs and their firing frequency. Our main findings are that there is reduced Ca(2+) entry on single AP stimulation, particularly in the axon proximal segment, reduced AP duration and reduced firing frequency to a 400 ms stimulation in α(2)δ-1 knockout neurons, consistent with the expected role of voltage-gated calcium channels in these events. Furthermore, lower intracellular Ca(2+) buffering also resulted in reduced AP duration, and a lower frequency of AP firing in WT neurons, mimicking the effect of α(2)δ-1 knockout. By contrast, we did not obtain any consistent evidence for the involvement of Ca(2+)-activation of large conductance calcium-activated potassium (BK) and small conductance calcium-activated potassium (SK) channels in these events. In conclusion, the reduced Ca(2+) elevation as a result of single AP stimulation is likely to result from the reduced duration of the AP in α(2)δ-1 knockout sensory neurons. This article is part of the themed issue ‘Evolution brings Ca(2+) and ATP together to control life and death’.