Pannexin-1 opening in neuronal edema causes cell death but also leads to protection via increased microglia contacts.

Neuronal swelling during cytotoxic edema is triggered by Na and Cl entry and is Ca independent. However, the causes of neuronal death during swelling are unknown. Here, we investigate the role of large-conductance Pannexin-1 (Panx1) channels in neuronal death during cytotoxic edema.

KCC2 drives chloride microdomain formation in dendritic blebbing.

Intracellular chloride ion concentration ([Cl]) homeostasis is critical for excitatory/inhibitory balance and volume regulation in neurons. We quantitatively map spatiotemporal dendritic [Cl] dynamics during N-methyl-d-aspartate (NMDA) excitotoxicity to determine how Cl changes contribute to localized dendritic swelling (blebbing) in stroke-like conditions. Whole-cell patch clamp electrophysiology combined with simultaneous fluorescence lifetime imaging (FLIM) of the Cl dye N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide (MQAE; MQAE-FLIM) reliably report resting and dynamic [Cl] shifts in dendrites.

Mitochondrial Ca uptake by the MCU facilitates pyramidal neuron excitability and metabolism during action potential firing.

Neuronal activation is fundamental to information processing by the brain and requires mitochondrial energy metabolism. Mitochondrial Ca uptake by the mitochondrial Ca uniporter (MCU) has long been implicated in the control of energy metabolism and intracellular Ca signalling, but its importance to neuronal function in the brain remains unclear. Here, we used in situ electrophysiology and two-photon imaging of mitochondrial Ca, cytosolic Ca, and NAD(P)H to test the relevance of MCU activation to pyramidal neuron Ca signalling and energy metabolism during action potential firing.

Ca transients in astrocyte fine processes occur via Ca influx in the adult mouse hippocampus.

Astrocytes display complex morphologies with an array of fine extensions extending from the soma and the primary thick processes. Until the use of genetically encoded calcium indicators (GECIs) selectively expressed in astrocytes, Ca signaling was only examined in soma and thick primary processes of astrocytes where Ca -sensitive fluorescent dyes could be imaged. GECI imaging in astrocytes revealed a previously unsuspected pattern of spontaneous Ca transients in fine processes that has not been observed without chronic expression of GECIs, raising potential concerns about the effects of GECI expression.

Ca2+ removal by the plasma membrane Ca2+-ATPase influences the contribution of mitochondria to activity-dependent Ca2+ dynamics in Aplysia neuroendocrine cells.

After Ca(2+) influx, mitochondria can sequester Ca(2+) and subsequently release it back into the cytosol. This form of Ca(2+)-induced Ca(2+) release (CICR) prolongs Ca(2+) signaling and can potentially mediate activity-dependent plasticity. As Ca(2+) is required for its subsequent release, Ca(2+) removal systems, like the plasma membrane Ca(2+)-ATPase (PMCA), could impact CICR.

PKC enhances the capacity for secretion by rapidly recruiting covert voltage-gated Ca2+ channels to the membrane.

It is unknown whether neurons can dynamically control the capacity for secretion by promptly changing the number of plasma membrane voltage-gated Ca(2+) channels. To address this, we studied peptide release from the bag cell neurons of Aplysia californica, which initiate reproduction by secreting hormone during an afterdischarge. This burst engages protein kinase C (PKC) to trigger the insertion of a covert Ca(2+) channel, Apl Cav2, alongside a basal channel, Apl Cav1.

Ca2+-induced uncoupling of Aplysia bag cell neurons.

Electrical transmission is a dynamically regulated form of communication and key to synchronizing neuronal activity. The bag cell neurons of Aplysia are a group of electrically coupled neuroendocrine cells that initiate ovulation by secreting egg-laying hormone during a prolonged period of synchronous firing called the afterdischarge. Accompanying the afterdischarge is an increase in intracellular Ca2+ and the activation of protein kinase C (PKC).

Separate Ca2+ sources are buffered by distinct Ca2+ handling systems in aplysia neuroendocrine cells.

Although the contribution of Ca(2+) buffering systems can vary between neuronal types and cellular compartments, it is unknown whether distinct Ca(2+) sources within a neuron have different buffers. As individual Ca(2+) sources can have separate functions, we propose that each is handled by unique systems. Using Aplysia californica bag cell neurons, which initiate reproduction through an afterdischarge involving multiple Ca(2+)-dependent processes, we investigated the role of endoplasmic reticulum (ER) and mitochondrial sequestration, as well as extrusion via the plasma membrane Ca(2+)-ATPase (PMCA) and Na(+)/Ca(2+) exchanger, to the clearance of voltage-gated Ca(2+) influx, Ca(2+)-induced Ca(2+)-release (CICR), and store-operated Ca(2+) influx.