Serotoninergic modulation of sensory transmission to brainstem reticulospinal cells

Sensory inputs are subjected to modulation by central neural networks involved in controlling movements. It has been shown that serotonin (5‐HT) modulates sensory transmission. This study examines in lampreys the effects of 5‐HT on sensory transmission to brainstem reticulospinal (RS) neurons and the distribution of 5‐HT cells that innervate RS cells. Cells were recorded intracellularly in the in vitro isolated brainstem of larval lampreys. Trigeminal nerve stimulation elicited disynaptic excitatory responses in RS neurons, and bath application of 5‐HT reduced the response amplitude with maximum effect at 10 μm. Local ejection of 5‐HT either onto the RS cells or onto the relay cells decreased sensory‐evoked excitatory postsynaptic potentials (EPSPs) in RS cells. The monosynaptic EPSPs elicited from stimulation of the relay cells were also reduced by 5‐HT. The reduction was maintained after blocking either N‐methyl‐d‐aspartate (NMDA) or α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionic acid (AMPA) receptors. The local ejection of glutamate over RS cells elicited excitatory responses that were only slightly depressed by 5‐HT. In addition, 5‐HT increased the threshold for eliciting sustained depolarizations in response to trigeminal nerve stimulation but did not prevent them. Combined 5‐HT immunofluorescence with axonal tracing revealed that the 5‐HT innervation of RS neurons of the middle rhombencephalic reticular nucleus comes mainly from neurons in the isthmic region, but also from neurons located in the pretectum and caudal rhombencephalon. Our results indicate that 5‐HT modulates sensory transmission to lamprey brainstem RS cells

Gβγ and the C Terminus of SNAP-25 Are Necessary for Long-Term Depression of Transmitter Release

Short-term presynaptic inhibition mediated by G protein-coupled receptors involves a direct interaction between G proteins and the vesicle release machinery. Recent studies implicate the C terminus of the vesicle-associated protein SNAP-25 as a molecular binding target of Gβγ that transiently reduces vesicular release. However, it is not known whether SNAP-25 is a target for molecular modifications expressing long-term changes in transmitter release probability.This study utilized two-photon laser scanning microscopy for real-time imaging of action potential-evoked [Ca(2+)] increases, in single Schaffer collateral presynaptic release sites in in vitro hippocampal slices, plus simultaneous recording of Schaffer collateral-evoked synaptic potentials. We used electroporation to infuse small peptides through CA3 cell bodies into presynaptic Schaffer collateral terminals to selectively study the presynaptic effect of scavenging the G-protein Gβγ. We demonstrate here that the C terminus of SNAP-25 is necessary for expression of LTD, but not long-term potentiation (LTP), of synaptic strength. Using type A botulinum toxin (BoNT/A) to enzymatically cleave the 9 amino acid C-terminus of SNAP-25 eliminated the ability of low frequency synaptic stimulation to induce LTD, but not LTP, even if release probability was restored to pre-BoNT/A levels by elevating extracellular [Ca(2+)]. Presynaptic electroporation infusion of the 14-amino acid C-terminus of SNAP-25 (Ct-SNAP-25), to scavenge Gβγ, reduced both the transient presynaptic inhibition produced by the group II metabotropic glutamate receptor stimulation, and LTD. Furthermore, presynaptic infusion of mSIRK, a second, structurally distinct Gβγ scavenging peptide, also blocked the induction of LTD. While Gβγ binds directly to and inhibit voltage-dependent Ca(2+) channels, imaging of presynaptic [Ca(2+)] with Mg-Green revealed that low-frequency stimulation only transiently reduced presynaptic Ca(2+) influx, an effect not altered by infusion of Ct-SNAP-25.The C-terminus of SNAP-25, which links synaptotagmin I to the SNARE complex, is a binding target for Gβγ necessary for both transient transmitter-mediated presynaptic inhibition, and the induction of presynaptic LTD

SNAP-25 is a novel effector of heterotrimeric G proteins modulating the strength of neurotransmission.

SNAP-25 is a novel effector of heterotrimeric G proteins modulating the strength of neurotransmission

Clostridium Difficile infection on an inpatient rehabilitation unit - Quality Improvement Project

Our Continuous Quality Improvement (CQI) project was focused on modifiable risk factors associated with Clostridium difficile infection (CDI) with ultimate goal to reduce CDI on the inpatient rehabilitation unit (IMR)

G␤␥ Interferes with Ca 2ϩ -Dependent Binding of Synaptotagmin to the Soluble N-Ethylmaleimide-Sensitive Factor Attachment Protein Receptor (SNARE) Complex

ABSTRACT Presynaptic inhibitory G protein-coupled receptors (GPCRs) can decrease neurotransmission by inducing interaction of G␤␥ with the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex. We have shown that this action of G␤␥ requires the carboxyl terminus of the 25-kDa synaptosomeassociated protein (SNAP25) and is downstream of the well known inhibition of Ca 2ϩ entry through voltage-gated calcium channels. We propose a mechanism in which G␤␥ and synaptotagmin compete for binding to the SNARE complex. Here, we characterized the G␤␥ interaction sites on syntaxin1A and SNAP25 and demonstrated an overlap of the G␤␥-and synaptotagmin I -binding regions on each member of the SNARE complex. Synaptotagmin competes in a Ca 2ϩ -sensitive manner with binding of G␤␥ to SNAP25, syntaxin1A, and the assembled SNARE complex. We predict, based on these findings, that at high intracellular Ca 2ϩ concentrations, Ca 2ϩ -synaptotagmin I can displace G␤␥ binding and the G␤␥-dependent inhibition of exocytosis can be blocked. We tested this hypothesis in giant synapses of the lamprey spinal cord, where 5-HT works via G␤␥ to inhibit neurotransmission . We showed that increased presynaptic Ca 2ϩ suppresses the 5-HT-and G␤␥-dependent inhibition of exocytosis. We suggest that this effect may be due to Ca 2

Gβγ interferes with Ca 2+ -dependent binding of synaptotagmin to the SNARE complex

[Ca 2+ ]; Ca 2+ concentration. SNAP25; Synaptosomal-associated protein of 25,000 dalton. MIANS; 2-(4'-maleimidylanilino) naphthalene-6-sulfonic acid. BoNT/A; botulinum toxin A. Synaptotagmin, Syt I (at MOL #39446 3 Abstract Presynaptic inhibitory GPCRs can decrease neurotransmission by inducing interaction of Gβγ with the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex. Previously, we showed that this action of Gβγ requires the carboxyl terminus of SNAP25 and is downstream of the well-known inhibition of Ca 2+ entry through voltage-gated calcium channels (VGCC). We proposed a mechanism in which Gβγ and synaptotagmin compete for binding to the SNARE complex. Here, we characterized the Gβγ interaction sites on syntaxin1A and SNAP25 and demonstrated an overlap of the Gβγ-and synaptotagmin I -binding regions on each member of the SNARE complex. Synaptotagmin competes in a Ca 2+ -sensitive manner with binding of Gβγ to SNAP25, syntaxin1A and the assembled SNARE complex. We predict based on these findings that at high intracellular Ca 2+ concentrations, Ca 2+ -synaptotagmin I can displace Gβγ binding, and the Gβγ-dependent inhibiton of exocytosis can be blocked. We tested this hypothesis in giant synapses of the lamprey spinal cord, where 5-HT works via Gβγ to inhibit neurotransmissio