Module 10: Figure tonic oscillations in DA neurons
Tonic oscillations in dopaminergic (DA) neurons.
Dopaminergic (DA) neurons have an autonomous oscillatory mechanism that generates a regular tonic firing pattern. The membrane potential (Vm) is unstable in that there is a slow pacemaker potential and this depolarization triggers an action potential at intervals of approximately 1 per second (see inset on the left). Operating in phase with this membrane oscillation, there are repetitive Ca2+ transients with each rising phase coinciding with the action potential while the slow falling phase occurs during the pacemaker period. The repetitive Ca2+ transients load up the mitochondria to enhance oxidative respiration and a resulting increase in the formation of reactive oxygen species (ROS). Inner mitochondrial membrane potential flickers, which occur at a much lower frequency (see lower inset on the left), may reflect the existence of a feedback mechanism to curb excess Ca2+ levels and ROS formation. See text for further details of the interplay between the membrane and intracellular Ca2+ oscillations. Information for this Figure was taken from the work of Jim Surmeier and his colleagues (Guzman et al., 2010; Surmeier et al., 2011).