Geochemistry of Pleistocene volcanic rocks in the Mariana Forearc

Geophysical surveys of the Mariana forearc, in an area equidistant from the Mariana Trench and the active Mariana Island Arc, revealed a 40-m-deep graben about 13 km northwest of Conical Seamount, a serpentine mud volcano. The graben and its bounding horst blocks are part of a fault zone that strikes northwest-southeast beneath Conical Seamount. One horst block was drilled during Leg 125 of the Ocean Drilling Program (Site 781). Three lithologic units were recovered at Site 781: an upper sedimentary unit, a middle basalt unit, and a lower sedimentary unit. The upper unit, between 0 and 72 mbsf, consists of upper Pliocene to Holocene diatomaceous and radiolarian-bearing silty clay that grades down into vitric silty clay and vitric clayey silt. The middle unit is a Pleistocene vesicular, porphyritic basalt, the top of which corresponds to a high-amplitude reflection on the reflection profiles. The lower unit is a middle to upper (and possibly some lower) Pliocene vitric silty clay and vitric clayey silt similar to the lower part of the upper unit. The thickness of the basalt unit can only be estimated to be between 13 and 25 m because of poor core recovery (28% to 55%). The absence of internal flow structures and the presence of an upper glassy chilled zone and a lower, fine-grained margin suggest that the basalt unit is either a single lava flow or a near-surface sill. The basalt consists of plagioclase phenocrysts with subordinate augite and olivine phenocrysts and of plagioclase-augite-olivine glomerocrysts in a groundmass of plagioclase, augite, olivine, and glass. The basalt is an island arc tholeiite enriched in large-ion-lithophile elements relative to high-field-strength elements, similar to the submarine lavas of the southern arc seamounts. In contrast, volcanic rocks from the active volcanoes on Pagan and Agrigan islands, 100 km to the west of the drill site, are calc-alkaline. The basalt layer, the youngest in-situ igneous layer reported from the Izu-Bonin and Mariana forearcs, is enigmatic because of its location more than 100 km from the active volcanic arc. The sediment layers above and below the basalt unit are late Pliocene in age (about 2.5 Ma) and normally magnetized. The basalt has schlierenlike structures, reverse magnetization, and a K-Ar age of 1.68±0.37 Ma. Thus, the basalt layer is probably a sill fed by magma intruded along a fault zone bounding the horst and graben in the forearc. The geochemistry of the basalt is consistent with a magma source similar to that of the active island arc and from a mantle source above the subducting Pacific plate.

Geochemistry of ash layers from the Bonin Forearc

Many ash-rich layers, varying from a few millimeters to several centimeters thick, were identified in the sedimentary sequences penetrated during Ocean Drilling Program Leg 125 at Sites 782, 784, and 786, located about 400 to 500 km south of Tokyo in the Bonin forearc. The total age range of the ash layers is from Eocene to Pleistocene, although not all sites cover this full span. The ashes consist of vitric, microlite-bearing, and crystal-rich components; the glassy shards are typically highly vesicular, with elongate, flattened bubbles. The dominant crystalline phases are orthopyroxene, clinopyroxene, and plagioclase. The major-element compositions of individual vitric shards collected from selected layers of Holes 782A, 784A, and 786A were determined by electron microprobe analyses; particular care was taken to ensure that the analytical results were not compromised by electron beam damage to the glasses. Compositions range from basalt through andesite and dacite to rhyolite and generally belong to a tholeiitic, low-K suite. There is no indication of any regular secular change during the evolution of the Bonin arc from tholeiitic through calc-alkalic to alkali compositions with time. In Holes 782A and 784A, some high-K rhyolite compositions of late Miocene and Pleistocene age are present. A clear chemical distinction has existed since arc inception between the source(s) of these ashes and the upper mantle source(s) tapped during construction of the igneous basement that formed the forearc.

Geochemistry of volcaniclastites of the western Pacific Ocean

Samples collected from the coarse basal portions of mid-Cretaceous volcaniclastic turbidites from the Mariana and Pigafetta basins are remarkably similar in terms of the petrographic and chemical features of their igneous clasts and bulk rock composition. Clasts of magmatic origin are dominated by glassy vesicular shards, variably phyric, holocrystalline basalts, and crystal fragments (olivine, clinopyroxene, plagioclase, amphibole, and biotite). The composition of the pyroxenes and amphiboles are typical of those found in differentiated hydrous alkali basalts. The bulk chemical composition of the volcaniclastites (based on stable incompatible elements and their ratios in highly vitric samples) is characteristic of alkali basalts found in within-plate oceanic eruptive environments. Miocene volcaniclastites from Site 802 are broadly similar to the Cretaceous samples in terms of clast type and bulk composition, and have also been derived from an oceanic alkali basalt source. The chemistry of the Miocene volcaniclastites differ, however, in having distinctive Zr/Y and Zr/Nb ratios and a more restricted chemical composition. The magmatic products of nearly emergent seamounts within the western Pacific basins appears to have been dominated by alkali basalt volcanism during the mid-Cretaceous and also the Miocene. The highly vitric nature of the Cretaceous and Miocene volcaniclastites, together with the morphology and vesicularity of their shards, suggests that they are the reworked (via mass flow) products of hyaloclastite accumulations produced in a shallow-water eruptive environment, such as that adjacent to nearly emergent seamounts or ocean islands. The association of ooids, reefal debris, and, in rare cases, woody material with the volcaniclastites supports their shallow-water derivation.

Composition of ODP Leg 126 sandstones

Early diagenesis in Leg 126 forearc and backarc sands/sandstones is characterized by the dissolution of intermediate to mafic brown glass, the alteration of colorless rhyolitic glass to clay minerals, precipitation of thin clay-mineral rim cements, and minor precipitation of clinoptilolite cements. Later, more intense diagenesis is restricted to Oligocene forearc basin sediments at Sites 787,792, and 793. In these sections, the effects of early diagenesis have been intensified and overprinted by later diagenetic effects including (1) large-scale dissolution of feldspar and pyroxene crystals, (2) further dissolution of vitric components, (3) precipitation of minor carbonate cements, and (4) pervasive, multiple-staged zeolite cementation. Zeolite minerals present include analcite, mordenite, natrolite, heulandite, wairakite, chabazite, erionite, herschelite, and phillipsite. The latest diagenetic events appear to be the minor dissolution of zeolite cements and the precipitation of minor carbonate and potassium feldspar(?) cements. Observed porosity types include primary interparticles; primary intraparticles in vesicular glass and foraminifers; primary interparticles reduced by compaction and cementation; secondary intraparticles produced by dissolution of feldspar, nonopaque heavy minerals, volcanic glass, and foraminifer tests; and secondary interparticles produced by the dissolution of zeolite cements. Within forearc Oligocene sections at Sites 787 and 792, diagenetic effects appear to decrease with depth in the Oligocene section; however, at Site 793 the majority of samples are intensely altered.

(Table 3) Age-related trends of desert pavement properties in the Transantarctic Mountains

Compared to mid-latitude deserts, the properties, formation and evolution of desert pavements and the underlying vesicular layer in Antarctica are poorly understood. This study examines the desert pavements and the vesicular layer from seven soil chronosequences in the Transantarctic Mountains that have developed on two contrasting parent materials: sandstone-dolerite and granite-gneiss. The pavement density commonly ranges from 63 to 92% with a median value of 80% and does not vary significantly with time of exposure or parent material composition. The dominant size range of clasts decreases with time of exposure, ranging from 16-64 mm on Holocene and late Quaternary surfaces to 8-16 mm on surfaces of middle Quaternary and older age. The proportion of clasts with ventifaction increases progressively through time from 20% on drifts of Holocene and late Quaternary age to 35% on Miocene-aged drifts. Desert varnish forms rapidly, especially on dolerite clasts, with nearly 100% cover on surfaces of early Quaternary and older age. Macropitting occurs only on clasts that have been exposed since the Miocene. A pavement development index, based on predominant clast-size class, pavement density, and the proportion of clasts with ventifaction, varnish, and pits, readily differentiated pavements according to relative age. From these findings we judge that desert pavements initially form from a surficial concentration of boulders during till deposition followed by a short period of deflation and a longer period of progressive chemical and physical weathering of surface clasts. The vesicular layer that underlies the desert pavement averages 4 cm in thickness and is enriched in silt, which is contributed primarily by weathering rather than eolian deposition. A comparison is made between desert pavement properties in mid-latitude deserts and Antarctic deserts.

Wet-bulk densities, mean atomic weights, effective porosities, grain densities, and compressional-wave velocities at DSDP Leg 58 Holes

The effects of water saturation and open pore space on the seismic velocities of crystalline rocks are extremely important when comparing laboratory data to in situ geophysical observations (e.g., Dortman and Magid, 1969; Nur and Simmons, 1969; Christensen and Salisbury, 1975). The existence of fractured rocks, flow breccias and drained pillows in oceanic crustal layer 2a, for instance, may appreciably reduce seismic velocities in that layer (Hyndman, 1976). Laboratory data assessing the influence of porosity and water saturation on seismic velocities of oceanic crustal rocks would certainly aid interpretation of marine geophysical data. Igneous rocks recovered during Leg 58 of the Deep Sea Drilling Project, in the Shikoku Basin and Daito Basin in the North Philippine Sea, are extremely vesicular, as evidenced by shipboard measurements of porosities, which range from 0 to 30 per cent (see reports on Sites 442, 443, 444, and 446, this volume). Samples with this range of porosities afford an excellent opportunity to examine the influence of porosity and water saturation on seismic velocities of oceanic basalts. This paper presents compressional-wave velocities to confining pressures of 1.5 kbars for water-saturated and air-dried basalt samples from the North Philippine Sea. Samples used in this study are from sites 442, 443 and 444 in the Shikoku Basin and Site 446 in the Daito Basin. Excellent negative correlation between porosity and compressional-wave velocity demonstrates that waterfilled pore space can significantly reduce compressionalwave velocities in porous basalts. Velocities measured in air-dried samples indicate that the velocity difference between dry samples and saturated samples is small for porosities exceeding 10 per cent, and very large for lower porosities.

Calidad poscosecha del tomate (Solanum lycopersicum L.) cultivado en sistemas ecológicos de fertilización

Se condujeron cuatro experimentos unifactoriales en condiciones de campo en áreas agrícolas de la Universidad de Granma, en el período comprendido de septiembre/2007 a enero/2010 para determinar el efecto de la aplicación de micorrizas arbusculares, Azotobacter chroococcum y ácidos húmicos sobre la productividad y la calidad poscosecha del tomate (Solanum lycopersicum L.) cv. “Vyta”, sobre un suelo de tipo Fluvisol. La aplicación simple y combinada de las micorrizas arbusculares, el Azotobacter chroococcum y los ácidos húmicos mostró un efecto positivo sobre la productividad de la variedad de tomate estudiada, al obtenerse incrementos significativos de este indicador en comparación con el control (sin aplicación), lográndose los mejores resultados con la combinación Glomus fasciculatum (0,3 kg m-2) + Azotobacter chroococcum (30 L ha-1) + ácidos húmicos (500 mg L-1) con valores de 54,57 t ha-1. Se comprobó además, que los tratamientos con estos bioproductos presentaron contenidos de sólidos solubles totales (SST), carbohidratos solubles totales (CST), vitamina C, porcentaje de materia seca (PMS), firmeza, longitud y anchura de los frutos superiores al control (sin aplicación). Las plantas controles (sin aplicación) significativamente incrementaron la acidez titulable (contenido de ácido cítrico) y la pérdida de peso y redujeron el pH de los frutos del tomate. Los análisis de correlación realizados revelan que existieron correlaciones positivas y significativas entre el contenido de vitamina C, materia seca, sólidos solubles totales, carbohidratos solubles totales, y el pH de los frutos, mientras que la acidez titulable presentó correlaciones negativas y significativas con todas las variables mencionadas anteriormente. Se encontró a su vez un efecto sinérgico en las plantas con la aplicación combinada de estos productos con respecto al control (sin aplicación), expresado en los mayores valores de los parámetros micorrízicos estudiados. ABSTRACT Four unifactorial experiments under field conditions in an agricultural area belonging to the University of Granma from September/2007 to January/2010 aiming to evaluate the effect of arbuscular mycorrhizas, Azotobacter and humic acids on tomato (Solanum lycopersicum L) cv. “Vyta” crop yield and postharvest quality in a Typic Fluvent soil were conducted. The simple and mixed application of arbuscular mycorrhizas, Azotobacter chroococcum and humic acids showed a positive effect on yield and internal postharvest parameters evaluated for the studied tomato variety, achieving significant increases with respect to the control treatment ones. The best results related to crop yield were achieved by combining Glomus fasciculatum (0.3 kg m-2) + Azotobacter chroococcum (30 L ha-1) + humic acids (500 mg L-1) that lead to 54.57 t ha-1. In addition, it was also demonstrated that the treatments under effect of biofertilizers and biostimulants resulted in higher total soluble solids (TSS), total soluble carbohydrates (TSC), vitamin C, dry matter contents (DMC), firmness, length and width of the fruits than the control treatment. The control plants showed significantly increased titrable acidity (citric acid content) and weight loss and reduced pH on the tomato fruits. The conducted correlation analyses revealed that there were significant and positive correlations between vitamin C content, dry matter, total soluble solids, total soluble carbohydrates, and pH of the fruit, while titratable acidity showed significant negative correlations with all variables mentioned above. At the same time, a synergic effect by mixed utilization of these biological products on tomato plants, with respect to control treatment (non-treated), was found regarding the increase of studied mycorrhizal parameters.

A nerve growth factor mimetic TrkA antagonist causes withdrawal of cortical cholinergic boutons in the adult rat

Cholinergic neurons respond to the administration of nerve growth factor (NGF) in vivo with a prominent and selective increase of choline acetyl transferase activity. This suggests the possible involvement of endogenous NGF, acting through its receptor TrkA, in the maintenance of central nervous system cholinergic synapses in the adult rat brain. To test this hypothesis, a small peptide, C(92-96), that blocks NGF-TrkA interactions was delivered stereotactically into the rat cortex over a 2-week period, and its effect and potency were compared with those of an anti-NGF monoclonal antibody (mAb NGF30). Two presynaptic antigenic sites were studied by immunoreactivity, and the number of presynaptic sites was counted by using an image analysis system. Synaptophysin was used as a marker for overall cortical synapses, and the vesicular acetylcholine transporter was used as a marker for cortical cholinergic presynaptic sites. No significant variations in the number of synaptophysin-immunoreactive sites were observed. However, both mAb NGF30 and the TrkA antagonist C(92-96) provoked a significant decrease in the number and size of vesicular acetylcholine transporter–IR sites, with the losses being more marked in the C(92-96) treated rats. These observations support the notion that endogenously produced NGF acting through TrkA receptors is involved in the maintenance of the cholinergic phenotype in the normal, adult rat brain and supports the idea that NGF normally plays a role in the continual remodeling of neural circuits during adulthood. The development of neurotrophin mimetics with antagonistic and eventually agonist action may contribute to therapeutic strategies for central nervous system degeneration and trauma.

Brefeldin A-inhibited guanine nucleotide-exchange activity of Sec7 domain from yeast Sec7 with yeast and mammalian ADP ribosylation factors

The Saccharomyces cerevisiae Sec7 protein (ySec7p), which is an important component of the yeast secretory pathway, contains a sequence of ≈200 amino acids referred to as a Sec7 domain. Similar Sec7 domain sequences have been recognized in several guanine nucleotide-exchange proteins (GEPs) for ADP ribosylation factors (ARFs). ARFs are ≈20-kDa GTPases that regulate intracellular vesicular membrane trafficking and activate phospholipase D. GEPs activate ARFs by catalyzing the replacement of bound GDP with GTP. We, therefore, undertook to determine whether a Sec7 domain itself could catalyze nucleotide exchange on ARF and found that it exhibited brefeldin A (BFA)-inhibitable ARF GEP activity. BFA is known to inhibit ARF GEP activity in Golgi membranes, thereby causing reversible apparent dissolution of the Golgi complex in many cells. The His6-tagged Sec7 domain from ySec7p (rySec7d) synthesized in Escherichia coli enhanced binding of guanosine 5′-[γ-[35S]thio]triphosphate by recombinant yeast ARF1 (ryARF1) and ryARF2 but not by ryARF3. The effects of rySec7d on ryARF2 were inhibited by BFA in a concentration-dependent manner but not by inactive analogues of BFA (B-17, B-27, and B-36). rySec7d also promoted BFA-sensitive guanosine 5′-[γ-thio]triphosphate binding by nonmyristoylated recombinant human ARF1 (rhARF1), rhARF5, and rhARF6, although the effect on rhARF6 was very small. These results are consistent with the conclusion that the yeast Sec7 domain itself contains the elements necessary for ARF GEP activity and its inhibition by BFA.

GIPC, a PDZ domain containing protein, interacts specifically with the C terminus of RGS-GAIP

We have identified a mammalian protein called GIPC (for GAIP interacting protein, C terminus), which has a central PDZ domain and a C-terminal acyl carrier protein (ACP) domain. The PDZ domain of GIPC specifically interacts with RGS-GAIP, a GTPase-activating protein (GAP) for Gαi subunits recently localized on clathrin-coated vesicles. Analysis of deletion mutants indicated that the PDZ domain of GIPC specifically interacts with the C terminus of GAIP (11 amino acids) in the yeast two-hybrid system and glutathione S-transferase (GST)-GIPC pull-down assays, but GIPC does not interact with other members of the RGS (regulators of G protein signaling) family tested. This finding is in keeping with the fact that the C terminus of GAIP is unique and possesses a modified C-terminal PDZ-binding motif (SEA). By immunoblotting of membrane fractions prepared from HeLa cells, we found that there are two pools of GIPC–a soluble or cytosolic pool (70%) and a membrane-associated pool (30%). By immunofluorescence, endogenous and GFP-tagged GIPC show both a diffuse and punctate cytoplasmic distribution in HeLa cells reflecting, respectively, the existence of soluble and membrane-associated pools. By immunoelectron microscopy the membrane pool of GIPC is associated with clusters of vesicles located near the plasma membrane. These data provide direct evidence that the C terminus of a RGS protein is involved in interactions specific for a given RGS protein and implicates GAIP in regulation of additional functions besides its GAP activity. The location of GIPC together with its binding to GAIP suggest that GAIP and GIPC may be components of a G protein-coupled signaling complex involved in the regulation of vesicular trafficking. The presence of an ACP domain suggests a putative function for GIPC in the acylation of vesicle-bound proteins.

VMAT2 knockout mice: Heterozygotes display reduced amphetamine-conditioned reward, enhanced amphetamine locomotion, and enhanced MPTP toxicity

The brain vesicular monoamine transporter (VMAT2) pumps monoamine neurotransmitters and Parkinsonism-inducing dopamine neurotoxins such as 1-methyl-4-phenyl-phenypyridinium (MPP+) from neuronal cytoplasm into synaptic vesicles, from which amphetamines cause their release. Amphetamines and MPP+ each also act at nonvesicular sites, providing current uncertainties about the contributions of vesicular actions to their in vivo effects. To assess vesicular contributions to amphetamine-induced locomotion, amphetamine-induced reward, and sequestration and resistance to dopaminergic neurotoxins, we have constructed transgenic VMAT2 knockout mice. Heterozygous VMAT2 knockouts are viable into adult life and display VMAT2 levels one-half that of wild-type values, accompanied by smaller changes in monoaminergic markers, heart rate, and blood pressure. Weight gain, fertility, habituation, passive avoidance, and locomotor activities are similar to wild-type littermates. In these heterozygotes, amphetamine produces enhanced locomotion but diminished behavioral reward, as measured by conditioned place preference. Administration of the MPP+ precursor N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine to heterozygotes produces more than twice the dopamine cell losses found in wild-type mice. These mice provide novel information about the contributions of synaptic vesicular actions of monoaminergic drugs and neurotoxins and suggest that intact synaptic vesicle function may contribute more to amphetamine-conditioned reward than to amphetamine-induced locomotion.

Selection and nuclear immobilization of exportable RNAs

The intracellular distribution of RNAs depends on interactions of cis-acting nuclear export elements or nuclear retention elements with trans-acting nuclear transport or retention factors. To learn about the relationship between export and retention, we isolated RNAs that are exported from nuclei of Xenopus laevis oocytes even when most RNA export is blocked by an inhibitor of Ran-dependent nucleocytoplasmic transport, the Matrix protein of vesicular stomatitis virus. Export of the selected RNAs is saturable and specific. When present in chimeric RNAs, the selected sequences acted like nuclear export elements in promoting efficient export of RNAs that otherwise are not exported; the pathway used for export of these chimeric RNAs is that used for the selected RNAs alone. However, these chimeric RNAs, unlike the selected RNAs, were not exported in the presence of Matrix protein; thus, the nonselected sequences can cause retention of the selected RNA sequences under conditions of impaired nucleocytoplasmic transport. We propose that most RNAs are transiently immobilized in the nucleus and that release of these RNAs is an essential and early step in export. Release correlates with functional Ran-dependent transport, and the lack of export of chimeric RNAs may result from interference with the Ran system.

Na,K-ATPase transport from endoplasmic reticulum to Golgi requires the Golgi spectrin–ankyrin G119 skeleton in Madin Darby canine kidney cells

Spectrin (βIΣ∗) and ankyrin (AnkG119) associate with Golgi membranes and the dynactin complex, but their role in vesicle trafficking remains uncertain. We find that the actin-binding domain and membrane-association domain 1 (MAD1) of βI spectrin together form a constitutive Golgi targeting signal in transfected MDCK cells. Expression of this signal in transfected cells disrupts the endogenous Golgi spectrin skeleton and blocks transport of α- and β-Na,K-ATPase and vesicular stomatitis virus-G protein from the endoplasmic reticulum (ER) but does not disrupt the formation of Golgi stacks, the distribution of β-COP, or the transport and surface display of E-cadherin. The Golgi spectrin skeleton is thus required for the transport of a subset of membrane proteins from the ER to the Golgi. We postulate that together with polyfunctional adapter proteins such as AnkG119, Golgi spectrin forms a docking complex that acts prior to the cis-Golgi, presumably with vesicular–tubular clusters (VTCs or ERGIC), to sequester specific membrane proteins into vesicles transiting between the ER and Golgi, and subsequently (probably involving other isoforms of spectrin and ankyrin) to mediate cargo transport within the Golgi and to other membrane compartments. We hypothesize that this vesicular spectrin–ankyrin adapter-protein trafficking (or tethering) system (SAATS) mediates the capture and transport of many membrane proteins and acts in conjunction with vesicle-targeting molecules to effect the efficient transport of cargo proteins.

Muscarinic stimulation of synaptic activity by protein kinase C is inhibited by adenosine in cultured hippocampal neurons

We have studied the effect of the cholinergic agonist carbachol on the spontaneous release of glutamate in cultured rat hippocampal cells. Spontaneous excitatory postsynaptic currents (sEPSCs) through glutamatergic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type channels were recorded by means of the patch-clamp technique. Carbachol increased the frequency of sEPSCs in a concentration-dependent manner. The kinetic properties of the sEPSCs and the amplitude distribution histograms were not affected by carbachol, arguing for a presynaptic site of action. This was confirmed by measuring the turnover of the synaptic vesicular pool by means of the fluorescent dye FM 1–43. The carbachol-induced increase in sEPSC frequency was not mimicked by nicotine, but could be blocked by atropine or by pirenzepine, a muscarinic cholinergic receptor subtype M1 antagonist. Intracellular Ca2+ signals recorded with the fluorescent probe Fluo-3 indicated that carbachol transiently increased intracellular Ca2+ concentration. Since, however, carbachol still enhanced the sEPSC frequency in bis(2-aminophenoxy)ethane-N,N,N′,N′-tetra-acetate-loaded cells, this effect could not be attributed to the rise in intracellular Ca2+ concentration. On the other hand, the protein kinase inhibitor staurosporine as well as a down-regulation of protein kinase C by prolonged treatment of the cells with 4β-phorbol 12-myristate 13-acetate inhibited the carbachol effect. This argues for an involvement of protein kinase C in presynaptic regulation of spontaneous glutamate release. Adenosine, which inhibits synaptic transmission, suppressed the carbachol-induced stimulation of sEPSCs by a G protein-dependent mechanism activated by presynaptic A1-receptors.

Patch-clamp and amperometric recordings from norepinephrine transporters: Channel activity and voltage-dependent uptake

Transporters for the biogenic amines dopamine, norepinephrine, epinephrine and serotonin are largely responsible for transmitter inactivation after release. They also serve as high-affinity targets for a number of clinically relevant psychoactive agents, including antidepressants, cocaine, and amphetamines. Despite their prominent role in neurotransmitter inactivation and drug responses, we lack a clear understanding of the permeation pathway or regulation mechanisms at the single transporter level. The resolution of radiotracer-based flux techniques limits the opportunities to dissect these problems. Here we combine patch-clamp recording techniques with microamperometry to record the transporter-mediated flux of norepinephrine across isolated membrane patches. These data reveal voltage-dependent norepinephrine flux that correlates temporally with antidepressant-sensitive transporter currents in the same patch. Furthermore, we resolve unitary flux events linked with bursts of transporter channel openings. These findings indicate that norepinephrine transporters are capable of transporting neurotransmitter across the membrane in discrete shots containing hundreds of molecules. Amperometry is used widely to study neurotransmitter distribution and kinetics in the nervous system and to detect transmitter release during vesicular exocytosis. Of interest regarding the present application is the use of amperometry on inside-out patches with synchronous recording of flux and current. Thus, our results further demonstrate a powerful method to assess transporter function and regulation.