Effect of an intracellular calcium chelator on the regulation of electrically evoked [³H]‐noradrenaline release from rat hippocampal slices

Abstract

1 The electrically (3 Hz, 5 min) evoked [3H]-noradrenaline ([3H]-NA) release from rat hippocampal slices was reduced by prior treatment of the slices with 1,2-bis(2-aminophenoxy)ethane-N,N,N'N'-tetraacetomethylester (BAPTA/AM) in a concentration-(10 to 500 JM) dependent manner (40% at 30 JM). Reduction of medium calcium from 1.3 to 0.5 mm caused a larger (70%) decrease. BAPTA free acid (100 mM), a non-permeable Ca2+-chelator had no significant effect.

Effects on K+ currents in rat cerebellar granule neurones of a membrane‐permeable analogue of the calcium chelator BAPTA

“…This may be due, at least in part, to the fact that many workers preincubate tissues in BAPTA-AM before recording (e.g. Fredholm & Hu, 1993;Tymianski et al, 1994), and thus will not see the effects that we describe here. It has been shown very recently that BAPTA-AM could block synaptically evoked field potentials in a fully reversible manner, without affecting the presynaptic volley or antidromically evoked responses (Ouanounou et al, 1995).…”

“…This compound has been utilized in studies on the effects of chelation of intracellular Ca2" (see e.g. Fredholm & Hu, 1993;Noda et al, 1993;Tymianski et al, 1994 (IKA, IKv and IKSO), and discuss why these cannot be explained in terms of chelation of intracellular Ca2" by BAPTA. Some of the data described here have been presented in preliminary form (Watkins & Mathie, 1995).…”

“…This compound has been utilized in studies on the effects of chelation of intracellular Ca2" (see e.g. Fredholm & Hu, 1993;Noda et al, 1993;Tymianski et al, 1994). However, in the course of our studies on the regulation of IKSO in CG neurones, we have found that BAPTA-AM, whilst attenuating the muscarinic modulation of this current (Watkins, Amos & Mathie, unpublished observations), also itself directly affected IKSO* We describe herein some effects of BAPTA-AM on three voltage-activated K+ currents in CG neurones (IKA, IKv and IKSO), and discuss why these cannot be explained in terms of chelation of intracellular Ca2" by BAPTA.…”

Adenosine, Adenosine Receptors and the Actions of Caffeine *

“…The electrically evoked, but not the spontaneous release of neurotransmitter is strongly dependent on the concentration of calcium in the extracellular environment (Fredholm & Hu 1993). On the other hand, the electrically evoked release is poorly affected by buffers of intracellular calcium, whereas the spontaneous transmitter release is strongly affected.…”

Mechanisms and Effects of Intracellular Calcium Buffering on Neuronal Survival in Organotypic Hippocampal Cultures Exposed to Anoxia/Aglycemia or to Excitotoxins

“…The advantages over using Ca 2ϩ binding proteins include a nondisruptive means to introduce the buffers into cells (Tsien, 1981), predictable Ca 2ϩ buffering properties, and the potential for reversing their physiological actions through inactivation and /or cellular extrusion (Ouanounou et al, 1996). The physiological effects of exogenous buffers are well characterized, including their presynaptic effects on attenuating neurotransmitter release (Adler et al, 1991;Niesen et al, 1991;Fredholm and Hu, 1993;Roberts, 1993;Robitaille et al, 1993;Winslow et al, 1994;Ouanounou et al, 1996;Spigelman et al, 1996), postsynaptic effects on neuronal membrane excitability (Marty and Neher, 1985;Lancaster and Nicoll, 1987;Kohr and Mody, 1991;Schwindt et al, 1992;Zhang et al, 1995), and Ca 2ϩ homeostasis (Neher, 1986;Neher and Augustine, 1992;Zhou and Neher, 1993;Tymianski et al, 1994a).…”