The thalamic low-threshold Ca2+ potential: a key determinant of the local and global dynamics of the slow (<1 Hz) sleep oscillation in thalamocortical networks

During non-rapid eye movement sleep and certain types of anaesthesia, neurons in the neocortex and thalamus exhibit a distinctive slow (<1 Hz) oscillation that consists of alternating UP and DOWN membrane potential states and which correlates with a pronounced slow (<1 Hz) rhythm in the electroencephalogram. While several studies have claimed that the slow oscillation is generated exclusively in neocortical networks and then transmitted to other brain areas, substantial evidence exists to suggest that the full expression of the slow oscillation in an intact thalamocortical (TC) network requires the balanced interaction of oscillator systems in both the neocortex and thalamus. Within such a scenario, we have previously argued that the powerful low-threshold Ca2+ potential (LTCP)-mediated burst of action potentials that initiates the UP states in individual TC neurons may be a vital signal for instigating UP states in related cortical areas. To investigate these issues we constructed a computational model of the TC network which encompasses the important known aspects of the slow oscillation that have been garnered from earlier in vivo and in vitro experiments. Using this model we confirm that the overall expression of the slow oscillation is intricately reliant on intact connections between the thalamus and the cortex. In particular, we demonstrate that UP state-related LTCP-mediated bursts in TC neurons are proficient in triggering synchronous UP states in cortical networks, thereby bringing about a synchronous slow oscillation in the whole network. The importance of LTCP-mediated action potential bursts in the slow oscillation is also underlined by the observation that their associated dendritic Ca2+ signals are the only ones that inform corticothalamic synapses of the TC neuron output, since they, but not those elicited by tonic action potential firing, reach the distal dendritic sites where these synapses are located

Mitochondrion-Related Organelles in Free-Living Protists

Editor: Jan Tachezy: Series Editor: Alexander Steinbüchel.-- First Online: 10 August 2019.Mitochondrion-related organelles (MROs) are organelles that have independently evolved from mitochondria in eukaryotes that live in low-oxygen conditions. These organelles are functionally diverse, possessing a range of ancestrally mitochondrial or horizontally acquired biochemical pathways. Early studies of MROs focused mainly on parasitic organisms; however, the past decade has seen a growing body of work on the MROs of free-living eukaryotes based on comparative genomics, making it possible to tease apart adaptations to low-oxygen conditions from adaptations to parasitism. Here, we review current knowledge of MROs in free-living eukaryotes.Peer reviewe