Receptor subunit compositions underly distinct potencies of a muscle relaxant in fast and slow muscle fibers.

A line of studies in the 1960s-1980s suggested that muscle relaxants do not work uniformly on all skeletal muscles, though its mechanism has not been clarified. We showed here that a classical non-depolarizing muscle relaxant pancuronium inhibits fast muscle fibers at lower concentration compared to slow muscle fibers in zebrafish. The difference of effective concentration was observed in locomotion caused by tactile stimulation as well as in synaptic currents of the neuromuscular junction induced by motor neuron excitation.

Spontaneously Recycling Synaptic Vesicles Constitute Readily Releasable Vesicles in Intact Neuromuscular Synapses.

Emerging evidence shows that spontaneous synaptic transmission plays crucial roles on neuronal functions through presynaptic molecular mechanisms distinct from that of action potential (AP)-evoked transmission. However, whether the synaptic vesicle (SV) population undergoing the two forms of transmission is segregated remains controversial due in part to the conflicting results observed in cultured neurons. Here we address this issue in intact neuromuscular synapses using transgenic zebrafish larvae expressing two different indicators targeted in the SVs: a pH-sensitive fluorescent protein, pHluorin, and a tag protein, HaloTag.

Quantitative Analysis of Presynaptic Vesicle Luminal pH in Cultured Neurons.

Newly generated synaptic vesicles (SVs) are re-acidified by the activity of the vacuolar-type H-ATPases. Since H gradient across SV membrane drives neurotransmitter uptake into SVs, precise measurements of steady-state vesicular pH and dynamics of re-acidification process will provide important information concerning the H-driven neurotransmitter uptake. Indeed, we recently demonstrated distinct features of steady state and dynamics of vesicular pH between glutamatergic vesicles and GABAergic vesicles in cultured hippocampal neurons.

Gastrointestinal Neurons Expressing HCN4 Regulate Retrograde Peristalsis.

Peristalsis is indispensable for physiological function of the gut. The enteric nervous system (ENS) plays an important role in regulating peristalsis. While the neural network regulating anterograde peristalsis, which migrates from the oral end to the anal end, is characterized to some extent, retrograde peristalsis remains unresolved with regards to its neural regulation.

Expression of plasma membrane calcium ATPases confers Ca/H exchange in rodent synaptic vesicles.

Ca transport into synaptic vesicles (SVs) at the presynaptic terminals has been proposed to be an important process for regulating presynaptic [Ca] during stimulation as well as at rest. However, the molecular identity of the transport system remains elusive. Previous studies have demonstrated that isolated SVs exhibit two distinct Ca transport systems depending on extra-vesicular (cytosolic) pH; one is mediated by a high affinity Ca transporter which is active at neutral pH and the other is mediated by a low affinity Ca/H antiporter which is maximally active at alkaline pH of 8.

Development of lentiviral vectors for efficient glutamatergic-selective gene expression in cultured hippocampal neurons.

Targeting gene expression to a particular subset of neurons helps study the cellular function of the nervous system. Although neuron-specific promoters, such as the synapsin I promoter and the α-CaMKII promoter, are known to exhibit selectivity for excitatory glutamatergic neurons in vivo, the cell type-specificity of these promoters has not been thoroughly tested in culture preparations. Here, by using hippocampal culture preparation from the VGAT-Venus transgenic mice, we examined the ability of five putative promoter sequences of glutamatergic-selective markers including synapsin I, α-CaMKII, the vesicular glutamate transporter 1 (VGLUT1), Dock10 and Prox1.

Unique pH dynamics in GABAergic synaptic vesicles illuminates the mechanism and kinetics of GABA loading.

GABA acts as the major inhibitory neurotransmitter in the mammalian brain, shaping neuronal and circuit activity. For sustained synaptic transmission, synaptic vesicles (SVs) are required to be recycled and refilled with neurotransmitters using an H(+) electrochemical gradient. However, neither the mechanism underlying vesicular GABA uptake nor the kinetics of GABA loading in living neurons have been fully elucidated.

miR-199a Links MeCP2 with mTOR Signaling and Its Dysregulation Leads to Rett Syndrome Phenotypes.

Rett syndrome (RTT) is a neurodevelopmental disorder caused by MECP2 mutations. Although emerging evidence suggests that MeCP2 deficiency is associated with dysregulation of mechanistic target of rapamycin (mTOR), which functions as a hub for various signaling pathways, the mechanism underlying this association and the molecular pathophysiology of RTT remain elusive. We show here that MeCP2 promotes the posttranscriptional processing of particular microRNAs (miRNAs) as a component of the microprocessor Drosha complex.

Monitoring of vacuolar-type H+ ATPase-mediated proton influx into synaptic vesicles.

During synaptic vesicle (SV) recycling, the vacuolar-type H(+) ATPase creates a proton electrochemical gradient (ΔμH(+)) that drives neurotransmitter loading into SVs. Given the low estimates of free luminal protons, it has been envisioned that the influx of a limited number of protons suffices to establish ΔμH(+). Consistent with this, the time constant of SV re-acidification was reported to be <5 s, much faster than glutamate loading (τ of ∼ 15 s) and thus unlikely to be rate limiting for neurotransmitter loading.

Valproic acid selectively suppresses the formation of inhibitory synapses in cultured cortical neurons.

Valproic acid (VPA) has been used to treat epileptic patients because of its ability to potentiate GABA signaling in the brain. Despite its clinical significance, VPA administration during pregnancy increases the risk of congenital abnormalities, such as neural tube defects and neurodevelopmental disorders including autism. Furthermore, recent studies revealed that early postnatal administration of VPA also leads to neurodevelopmental deficits in rodents.

Involvement of the p75(NTR) signaling pathway in persistent synaptic suppression coupled with synapse elimination following repeated long-term depression induction.

Synaptic plasticity, especially structural plasticity, is thought to be a basis for long-lasting memory. We previously reported that, in rat hippocampus slice cultures, repeated induction of long-term depression (LTD) by application of a metabotropic glutamate receptor (mGluR) agonist led to slowly developing, long-lasting synaptic suppression coupled with synapse elimination. We referred to this phenomenon as LOSS (LTD-repetition-operated synaptic suppression) to discriminate it from conventional single LTD and proposed it as a model for analyzing structural plasticity.

Long-lasting synaptic loss after repeated induction of LTD: independence to the means of LTD induction.

Short- and long-lasting synaptic plasticity is assumed to be the cellular basis of short- and long-lasting memory, respectively. However, the cellular consequences leading to the long-lasting synaptic plasticity, assumed to include the processes of synapse formation and elimination, remain unknown. Using hippocampal slices maintained stably in culture, we found previously that the repeated induction of long-term potentiation (LTP) triggered a slowly developing long-lasting enhancement in synaptic transmission strength accompanied by synapse formation, which was separate from LTP itself.

A mono-2-ethylhexyl phthalate hydrolase from a Gordonia sp. that is able to dissimilate di-2-ethylhexyl phthalate.

Gordonia sp. strain P8219, a strain able to decompose di-2-ethylhexyl phthalate, was isolated from machine oil-contaminated soil. Mono-2-ethylhexyl phthalate hydrolase was purified from cell extracts of this strain.

Repetition of mGluR-dependent LTD causes slowly developing persistent reduction in synaptic strength accompanied by synapse elimination.

Synaptic plasticity, the cellular basis of memory, operates in a bidirectional manner. LTP (long-term potentiation) is followed by structural changes that may lead to the formation of new synapses. However, little is known whether LTD (long-term depression) is followed by morphological changes.