Rapid sprouting of filopodia in nerve terminals of chromaffin cells, PC12 cells, and dorsal root neurons induced by electrical stimulation

Abstract

Rapid morphological changes induced by direct electrical stimulation of nerve terminals were studied by using video-enhanced differential interference contrast microscopy at a very high magnification (12,000x). We used mainly cultured bovine chromaffin cells, which developed neurite-like processes, and PC12 cells, which showed neuronal differentiation upon NGF treatment. In a few cases, primary neurons of the rat dorsal root ganglion were also examined. Brief pulse stimulation of the terminals and varicosities induced exocytosis accompanied by rapid formation of filopodia. These filopodia, 0.1–0.2 micron in diameter and up to 10 microns in length, formed within a few hundreds of milliseconds and then retracted within tens of seconds. They could also be induced by K depolarization. This rapid filopodial sprouting strongly depended on the presence of extracellular Ca2+ and could be abolished in a medium containing a Ca chelator (EGTA) or La2+. Anti-cytoskeletal agents colchicine and cytochalasin B failed to block this response completely but lidocaine fully suppressed it. Quantitative analysis of exocytosis and filopodial sprouting showed that they were independent events, not directly linked to each other, having different thresholds usually higher for filopodial formation. In PC12 cells, the extent of filopodial sprouting varied with the state of differentiation of the cells, suggesting a functional role of rapid sprouting during a particular phase of their differentiation. Filopodia could be induced with greater ease by repetitive stimulation. The same responses may occur at growth cones approaching the target cells or even at mature synapses particularly after repetitive electrical activity, possibly playing a role in use-dependent synapse formation or plasticity.

Membrane shaping by actin and myosin during regulated exocytosis

“…In PC12 cells stimulation has been observed to lead to rapid sprouting of filopodia (Manivannan and Terakawa, 1994). This activity-dependent growth of filopodia is F-actin and myosin II dependent and leads to an increase in chromaffin and PC12 cell footprint size (Fig.…”

Decay in Prepulse Facilitation of Calcium Channel Currents by Gi/o-Protein Attenuation in Hamster Submandibular Ganglion Neurons, But Not Gq/11.

“…In particular, G i , G o and G q/11 transduce hormone and neurotransmitter receptormediated modulation of ion channels 4,11,23,40) . In neurons, transmembrane Ca ‫ם2‬ entry via voltage-dependent calcium channels (VDCCs) is of major physiological importance, because several neuronal functions such as neuronal excitability 29) , neuronal migration 28) , neurite outgrowth 25,30,34) , gene expression, and neurotransmitter release, depend on this event.…”

Single session of brief electrical stimulation immediately following crush injury enhances functional recovery of rat facial nerve

“…ES of nerve terminals has been shown to induce rapid filopodial sprouting in primary neuron cell cultures in the presence of extracellular Ca 2+ [3]. It has also been reported that, following sciatic nerve crush injury in rats, administering ES accelerates the appearance of the toespreading reflex, a sensitive indicator of the onset of motor recovery [8], further supporting the concept that ES enhances early regeneration events that initiate sprout formation.…”

“…Our initial studies investigated the therapeutic potential of ES in nerve regeneration following a rat facial nerve crush injury because of ES's enhancing effects on the morphological and functional properties of neurons [1][2][3][4]. In these studies, daily, low-frequency ES hastened the onset of recovery of the eye blink reflex by reducing the initial delay in sprout formation rather than by increasing the rate of axonal regeneration, indicating that ES acts primarily on events in the early stages of recovery [5][6][7].…”

“…Applying electrical stimulation (ES) has been shown to affect morphological and functional properties of neurons such as nerve branching, rate and orientation of neurite growth, rapid sprouting, and guidance during axon regeneration [1][2][3][4]. Therefore, ES has been explored as a therapeutic strategy for improving the outcome of peripheral nerve injury.…”