Release of calcium ions linked to the activation of potassium conductance in a caffeine‐treated sympathetic neurone.

Abstract

SUMMARY1. The mechanism of spontaneous and rhythmic hyperpolarizations which occur in bullfrog sympathetic ganglion cells under the effect of caffeine (2-10 mM) were further analysed.2. Intracellular injection ofEGTA blocked generation of caffeine hyperpolarizations (C-hyperpolarizations): this confirmed the previous conclusion (Kuba & Nishi, 1976) that these hyperpolarizations are caused by rhythmic increases in the K+ conductance (GK) of the membrane as a result of rises in free intracellular Ca2+.3. The amplitude and duration of a C-hyperpolarization induced by an action potential was a function of the time since the previous one; the longer the interval, greater the area.4. The relationship between the product of the amplitude and duration of a Chyperpolarization and the preceding interval depended on external Ca2+; when this was low the relationship shifted, so as to indicate an involvement of a Ca2+ accumulating process in the generation mechanism of C-hyperpolarizations.5. A rapid lowering of temperature triggered the generation of a C-hyperpolarization before appearance of a rhythmic one. There seemed to be no threshold temperature for the effect of such a cold shock; cooling from any temperature within a certain range (10-25 0C) by more than a few degrees was effective.6. The rapid cooling effect was observed even in a Ca2+-free Mg2+ solution. 7. Dantrolene Na increased the interval between rhythmic C-hyperpolarizations or blocked them, but affected less those triggered by an action potential or cold shock.8. Intracellular injection of Ca2+ triggered the generation of a C-hyperpolarization before the appearance of a rhythmic one.9. The latency of the generation of an action potential-evoked C-hyperpolarization was dependent on the preceding interval; the shorter the interval, the longer the latency. There was a refractory period for induction of an action potential-induced C-hyperpolarization.10. The interval between rhythmic C-hyperpolarizations was increased by a small or moderate membrane hyperpolarization (5-20 mV) and decreased by a larger * Present address.

[Ca2+] Signaling between Mitochondria and Endoplasmic Reticulum in Neurons Is Regulated by Microtubules

“…4D) and Ca 2ϩ -free solution (Fig. 4E), possibly reflecting a requirement for Ca 2ϩ influx in the activation of the CICR mechanism in neurons (42,43). Thapsigargin, a SERCA inhibitor, depleted the ER (34) as revealed by a slow [Ca 2ϩ ] i transient (Fig.…”

All-or-None Ca2+Release from Intracellular Stores Triggered by Ca2+Influx through Voltage-Gated Ca2+Channels in Rat Sensory Neurons

“…Ryanodine receptors are selectively modulated by and named after a plant alkaloid that blocks the channel at high concentrations (Ͼ100 M) and locks the channel in an open subconductance state at lower concentrations (Fill and Coronado, 1988). On the basis of a sensitivity to ryanodine and other modulators of C a 2ϩ stores, it has been suggested that CICR plays a role in a number of neuronal processes, including cell excitability (Kuba, 1980;Currie and Scott, 1992), neurotransmission (Peng, 1996), cell development and differentiation (Holliday et al, 1991;Gomez et al, 1995), and synaptic plasticity (Obenaus et al, 1989;Reyes and Stanton, 1996;Wang et al, 1996). Although functional ryanodine-sensitive stores are present in neurons and seem to participate in physiological processes, it is not clear how the stores contribute functionally to Ca 2ϩ signaling.…”

A brain‐specific transcript from the 3′‐terminal region of the skeletal muscle ryanodine receptor gene

“…Nucleotide residue 15230 is followed by a poly(dA) tract. The 5'-terminal residue of the sequence carried by each cDNA clone from brain libraries is indicated by filled circle (see section 2.2); the marks for the cDNA clones IBRRZ, 3,4,6,313 and 319 are omitted. The boundaries where the cDNA sequence is interrupted by introns in genomic DNA are shown by arrows; four exon-intron boundaries were determined in this study.…”