Ca²⁺or Sr²⁺Partially Rescues Synaptic Transmission in Hippocampal Cultures Treated with Botulinum Toxin A and C, But Not Tetanus Toxin

Abstract

Botulinum (BoNT/A-G) and tetanus toxins (TeNT) are zinc endopeptidases that cleave proteins associated with presynaptic terminals (SNAP-25, syntaxin, or VAMP/synaptobrevin) and block neurotransmitter release. Treatment of hippocampal slice cultures with BoNT/A, BoNT/C, BoNT/E, or TeNT prevented the occurrence of spontaneous or miniature EPSCs (sEPSCs or mEPSCs) as well as the [Ca 2ϩ ] o -independent increase in their frequency induced by phorbol ester, 0.5 nM ␣-latrotoxin, or sucrose. [Ca 2ϩ ] o -independent and -dependent release thus requires that the target proteins of clostridial neurotoxins be uncleaved. In contrast, significant increases in mEPSC frequency were produced in BoNT-treated, but not -dependent release was assessed by recordings from monosynaptically coupled CA3 cell pairs. The paired-pulse ratio of unitary EPSCs evoked by two presynaptic action potentials in close succession was 0.5 in control cultures, but it was 1.4 and 1.2 in BoNT/A-or BoNT/C-treated cultures when recorded in 10 mM [Ca 2ϩ ] o . Log-log plots of unitary EPSC amplitude versus [Ca 2ϩ ] o were shifted toward higher [Ca 2ϩ ] o in BoNT/A-or BoNT/C-treated cultures, but their slope was unchanged and the maximal EPSC amplitudes were reduced. We conclude that BoNTs reduce the Ca 2ϩ sensitivity of the exocytotic machinery and the number of quanta released.

Role of Extracellular Signal-Regulated Kinase in Synaptic Transmission and Plasticity of a Nociceptive Input on Capsular Central Amygdaloid Neurons in Normal and Acid-Induced Muscle Pain Mice

“…Since PDA has been shown to enhance glutamate release at many synapses in the brain (Malenka et al, 1986;Shapira et al, 1987;Parfitt and Madison, 1993;Capogna et al, 1997;Hori et al, 1999;Francis et al, 2002;Lou et al, 2008), we tested its effect on the PPR of PBA-CeAC EPSCs, an approach that is sensitive to presynaptic modulation (Zucker and Regehr, 2002). As shown in Figure 3, A and B, the PDA-induced potentiation of PBA-CeAC EPSCs was associated with a decrease in the PPR (baseline PPR 1.42 Ϯ 0.33, PPR during PDA application 0.73 Ϯ 0.32; n ϭ 5 cells, p Ͻ 0.001, paired t test), showing presynaptic modulation by PDA.…”

Astrocytes Display Complex and Localized Calcium Responses to Single-Neuron Stimulation in the Hippocampus

“…To address whether neurotransmitter released from axons of ChR2-infected neurons was responsible for glial calcium signaling after stimulation, we performed experiments in slices pretreated with TeNT (16 -24 h), which potently blocks synaptic transmission by cleaving vesicleassociated membrane protein (VAMP)/synaptobrevin (Schiavo et al, 1992;Capogna et al, 1997;Verderio et al, 1999). We verified the effectiveness of this toxin by measuring evoked potentials in CA1 cells of organotypic slices incubated with and without TeNT.…”

Ionic dependence of Ca 2+ channel modulation by syntaxin 1A

“…Other divalent cations such as Ba 2ϩ and Sr 2ϩ are able to move through Ca 2ϩ channels and mimic Ca 2ϩ action (1)(2)(3)(4)(5). The divalent charge carriers affect transmitter release at the neuromuscular junction (1,(5)(6)(7) and the squid giant synapse (3) as well as the neuronal (8)(9)(10)(11)(12)(13) and neuroendocrine cells (14).…”