1. Ca2+-induced uncoupling of Aplysia bag cell neurons.
- Author
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Dargaei Z, Standage D, Groten CJ, Blohm G, and Magoski NS
- Subjects
- Animals, Aplysia, Calcium-Calmodulin-Dependent Protein Kinase Type 2 antagonists & inhibitors, Electrical Synapses metabolism, Electrical Synapses physiology, Endoplasmic Reticulum metabolism, Mitochondria metabolism, Models, Neurological, Neurons drug effects, Neurons metabolism, Protein Kinase C antagonists & inhibitors, Synaptic Transmission, Action Potentials, Calcium metabolism, Calcium Signaling, Neurons physiology
- Abstract
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). We used whole cell recording from paired cultured bag cell neurons to demonstrate that electrical coupling is regulated by both Ca2+ and PKC. Elevating Ca2+ with a train of voltage steps, mimicking the onset of the afterdischarge, decreased junctional current for up to 30 min. Inhibition was most effective when Ca2+ entry occurred in both neurons. Depletion of Ca2+ from the mitochondria, but not the endoplasmic reticulum, also attenuated the electrical synapse. Buffering Ca2+ with high intracellular EGTA or inhibiting calmodulin kinase prevented uncoupling. Furthermore, activating PKC produced a small but clear decrease in junctional current, while triggering both Ca2+ influx and PKC inhibited the electrical synapse to a greater extent than Ca2+ alone. Finally, the amplitude and time course of the postsynaptic electrotonic response were attenuated after Ca2+ influx. A mathematical model of electrically connected neurons showed that excessive coupling reduced recruitment of the cells to fire, whereas less coupling led to spiking of essentially all neurons. Thus a decrease in electrical synapses could promote the afterdischarge by ensuring prompt recovery of electrotonic potentials or making the neurons more responsive to current spreading through the network., (Copyright © 2015 the American Physiological Society.)
- Published
- 2015
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