Characteristics of Ca2+ release induced by Ca2+ influx in cultured bullfrog sympathetic neurones.

Abstract

SUMMARY1. A rise in intracellular Ca21 ([Ca2+]i) and a Ca2+ current (ICa) induced by a depolarizing pulse were simultaneously recorded by fura-2 or indo-1 fluorescence and whole-cell patch clamp techniques in cultured bullfrog sympathetic ganglion cells. 2.[Ca2+]i (calculated from the ratio of fura-2 fluorescences excited at 380 and 340 nm and recorded with a photomultiplier at > 492 nm) rose regeneratively (in most cells) during a command pulse (from -60 to 0 mV, 100 ms), continued to rise thereafter, peaked at 666 ms (on average) and decayed slowly with a half-decay time of 22-8 s.3. Scanning a single horizontal line across the cytoplasm with an ultraviolet argon ion laser (351 nm) and recording indo-1 fluorescences at two wavelengths ( 6. Increasing the duration of depolarization (-50

Cyclic ADP-ribose Enhances Coupling between Voltage-gated Ca2+ Entry and Intracellular Ca2+ Release

“…This suggested that cADPR allowed the extra Ca 2ϩ entry evoked by depolarizations longer than 100 ms, to trigger even further release of Ca 2ϩ from the intracellular stores. We noted that the values of the unit transient were similar to those observed in isolated dorsal root ganglion cells (33,36), but approximately 10 ϫ larger than those observed in bullfrog neurons (29). This difference could relate to the much larger amplitude of the Ca 2ϩ currents in the bullfrog neurons and may reflect a greater degree of Ca 2ϩ buffering of the larger Ca 2ϩ entry compared with the smaller currents evoked in these mammalian neurons.…”

Release and sequestration of calcium by ryanodine‐sensitive stores in rat hippocampal neurones

“…Role of ryanodine-sensitive Ca¥ stores in CICR Contrasting the view that neuronal ryanodine-sensitive Ca¥ stores are essentially buffers of cytosolic Ca¥, is the view that these stores participate in the boosting of incoming Ca¥ signals via a CICR mechanism (Hua et al 1993;Llano et al 1994;Shmigol, Verkhratsky and Isenberg, 1995;Kano et al 1995), and thus may have a crucial role in neuronal plasticity (Schiegg et al 1995;Reyes & Stanton, 1996;Wang et al 1996) and excitotoxicity (see Mody & MacDonald, 1995). This view contends that, like in cardiac muscle (Nabauer et al 1989), cytosolic Ca¥ acts as a RyR agonist to discharge Ca¥ from the stores.…”

“…In some neurones Ca¥ entry through voltage-gated Ca¥ channels was shown to induce release of Ca¥ from ryanodine-sensitive Ca¥ stores (Friel & Tsien, 1992;Hua et al 1993;Llano et al 1994). To test for the presence of CICR, we examined whether depolarization-evoked Ca¥ transients are affected by depletion of ryanodine-sensitive Ca¥ stores (Fig.…”

“…Much less is known about the function of these stores in central neurones, despite the fact that all known members of the ryanodine receptor (RyR) family, namely, skeletal muscle type (type I), cardiac muscle type (type II) and brain type (type III), are abundantly expressed in the central nervous system (Furuichi, Furutama, Hakamata, Nakai, Takeshima & Mikoshiba, 1994). According to one hypothesis, RyRs in peripheral and central neurones amplify and prolong incoming Ca¥ signals via Ca¥-induced Ca¥ release (CICR) from the ryanodinesensitive Ca¥ stores (Holliday, Adams, Sejnowski & Spitzer, 1991;Hua, Nohmi & Kuba, 1993;Llano, DiPolo & Marty, 1994;Kano, Garaschuk, Verkhratsky & Konnerth, 1995), thus sharing functional properties with cardiac muscle RyRs (Fabiato, 1983;Nabauer, Callewaert, Cleemann & Morad, 1989). Accordingly, tetanic synaptic stimulation of CA1 pyramidal cells in a slice preparation reportedly induced Ca¥ release from dendritic ryanodine-sensitive Ca¥ stores (Alford, Frenguelli, Schofield & Collingridge, 1993).…”

Synaptic Transmission Mediated by Internal Calcium Stores in Rod Photoreceptors

“…An alternative possibility is that calcium influx recruits calcium from internal stores. In many neurons, transmitter release is influenced by intracellular calcium release in addition to calcium influx (Hua et al, 1993;Llano et al, 1994;Bouchard et al, 2003).…”