bluuebunny/crossref_metadata_2025 huggingface dataset:
Silica‐modified carbon paste electrode for copper determination in ammoniacal medium
Authors: Walcarius A. , Bessiere J.
Published: May 2005

The silica modified carbon paste electrode (SMCPE) was applied to the voltammetric detection of copper(II) at trace level after its accumulation under open‐circuit conditions. As demonstrated by cyclic voltammetric experiments, silica particles displayed an attractive ability to efficiently preconcentrate trace copper(II) from ammonia solution, according to a combined acid‐base and complexation reaction: 2 (SiOH) + Cu(NH3) ⇌ (SiO)2Cu(NH3)2 + 2 NH. The analytical procedure involved four successive steps: the preconcentration during a given period of time at open circuit in the ammoniated analyte solution, the medium exchange of the electrode (washed with water) to a pure electrolyte solution (0.1 M HNO3), a 30 s electrolysis for reducing the accumulated CuII species, and the square wave voltammetric determination. Experimental parameters affecting either the uptake of copper(II) or its voltammetric detection at SMCPE were explored, including the solution pH and ionic strength, the ammonia concentration in the preconcentration medium, the preconcentration time, the deposition potential and duration, the anodic stripping scan mode or the silica loading into the paste. A detection limit of 2 × 10−9 M has been achieved after 10 min preconcentration (from a 0.5 M NH3 medium), as determined for a signal‐to‐noise ratio of 3, and a linear calibration plot was obtained in the 5 × 10−9 M to 5 × 10−6 M concentration range. The relative standard deviation (n = 8) for the determination of a 5 × 10−7 M Cu11 sample was 8%.
Formation in situ and electrochemistry of C70‐salt film on a microelectrode
Authors: Cheng Fu‐Xiang , Li Nan‐Qiang , He Wei‐Jun , Gu Zhen‐Nan , Zhou Xi‐Huang , Sun Yi‐Liang , Wu Yong‐Qing
Published: May 2005

The first electrodeposition in situ of C70‐salt films in a mixed solvent on a microdisk electrode is reported. The deposition conditions of these films were optimized and then the electrochemical behaviors of these films were investigated, displaying three one‐electron oxidation peaks with the characteristics of surface reactions. The electron‐transfer coefficients (α) of the three surface reactions were also determined.
Electrooxidation of ammonia and simple amines at titanium electrodes modified with a mixture of ruthenium and titanium dioxides
Authors: Donten Mikołaj , Hyk Wojciech , Ciszkowska Małgorzata , Stojek Zbigniew
Published: May 2005

Electrooxidation of ammonia at the Ti/TiO2/RuO2 electrode was investigated using voltammetry, coulometry, 14N NMR, potentiometry with a nitrate ISE, and numerical simulation. The major product of electrooxidation was elementary nitrogen. Nitrate was a minor product. NH4 is not electroactive at the oxide electrode. Since protons are formed in the course of the electrode reaction, incoming ammonia is transformed to NH4, and therefore the flux of ammonia to the electrode surface is strongly depressed in solutions containing no excess of hydroxide ion. Amines were electrooxidized to a variety of compounds. Both ammonia and amines strongly adsorb on the electrode surface. Height of the anodic voltammetric peaks of both ammonia and simple amines was found to be linearly dependent on substrate concentration in a wide millimolar range.
Separation of the depolarizer from surface active substances in the tubes of a flow injection system
Authors: Kubiak Wladyslaw W. , Strozik Miroslaw M.
Published: May 2005

The possibility to separate depolarizer and surfactant bands directly in a flow injection system is reported. Transport of a surfactant is according to an adsorptive or a hydrodynamic mechanism. In the former case a surfactant is transported slower than a depolarizer whereas in the latter case it is transported faster than a depolarizer. Theoretical background for both mechanisms is provided. The influence of sample volume, mixing coil parameters (tube length and inner diameter), tube material and flow rate on the separation process is discussed. The separation process dependence on the flow rate may provide the basis of surface active substances characterization. Such characteristics for several surfactants are presented. Under optimized conditions the parameters of the calibration plots for a depolarizer in the absence and presence of surfactant are statisticaly equivalent.
Voltammetry and LCEC of isoflavones
Authors: Wu Langyu , Laughlin James B. , Dewald Howard D.
Published: May 2005

This study provides electrochemical and LCEC determination for three of the most abundant and most important isoflavones, Biochanin A, formononetin, and genistein. Cyclic voltammetry and pH‐potential diagrams show that the isoflavones undergo pH‐dependent irreversible oxidations. The LCEC determination of the isoflavones has been optimized for mobile phase composition and detection potential. Sub‐nanogram detection limits have been achieved.
Polarographic determination of hydrogen peroxide in perborate containing commercial detergents under the bleaching process condition
Authors: Sužnjević Desanka , Blagojević Stevan , Vučelić Dušan , Zuman Petr
Published: May 2005

Differential pulse (DP) and current sampled (TAST) polarography were applied for measuring hydrogen peroxide in actual washing systems. In addition to the possibility of the hydrogen peroxide determination in commercial detergent species containing sodium perborate monohydrate as bleaching substance, the change in peroxide concentration can be followed under the conditions which usually exist in the washing process. The possibility of determining dissolved oxygen in the peroxide decomposition reaction was also demonstrated.
Anion partitioning into highly lipophilic organic phases
Authors: Andredakis George , Tsagatakis John , Chaniotakis Nikolas A.
Published: May 2005

The partitioning of anions into different highly lipophilic media such as plasticizers used in the construction of ISEs was studied. Using both potentiometry and conductometry, precise partitioning values of a series of common potassium salts were obtained. The partitioning of the anions was shown to be significant and was dependent on the organic media used. These results stress the importance of the materials used in the construction of the anion selective electrodes since they gave anion partitioning sequences linked to the plasticizer, which differ from the common Hofmeister selectivity pattern. At the same time the partitioning values obtained can be used for the experimental estimation of the mobilities of anions in organic media.
Sol‐gel‐derived cobalt phthalocyanine‐dispersed carbon composite electrodes for electrocatalysis and amperometric flow detection
Authors: Wang Joseph , Pamidi Prasad V. A. , Parrado Concepcion , Park Deog Su , Pingarron Jose
Published: May 2005

A new sol‐gel‐derived electrocatalytic carbon composite electrode was prepared by dispersing cobalt phthalocyanine (CoPC) in a carbon ceramic network. The performance of the CoPC‐modified sol‐gel carbon composite electrode compares favorably with that of common CoPC‐containing carbon pastes in term of electrocatalytic properties and short‐ and long‐term stability. The greatly improved stability and electrocatalytic action are illustrated in cyclic‐voltammetric and flow injection amperometric measurements of hydrogen peroxide, hydrazine, oxalic acid, cysteine and thiourea. Such improvements are coupled with the versatility, mechanical stability and renewability features of sol‐gel carbon composites.
Anodic and cathodic stripping voltammetry in the simultaneous determination of toxic metals in environmental samples
Authors: Locatelli Clinio
Published: May 2005

Differential pulse anodic and cathodic stripping voltammetry have been employed for the simultaneous determination of AsIII, SeIV CuII, PbII and CdII in environmental matrices. The voltammetric measurements were carried out using a conventional three‐electrode cell and the ammonia‐ammonium chloride buffer (pH 9.2) as supporting electrolyte. The analytical procedure was verified by the analysis of the standard reference materials: Mussel Tissue BCR‐CRM 278 and Ulva Lactuca BCR‐CRM 279. The precision and the accuracy, expressed as relative standard deviation (sr) and relative error (e), respectively, were of the order of 3 to 5%, while the detection limit for each element, under the experimental conditions employed, was around 10−9 M.
Study of bimolecular interactions by molecular modeling and surface acoustic wave device
Authors: Thompson Michael , Frank M. Donata , Stone David C.
Published: May 2005

A film containing vicinal diol groups has been formed on the quartz surface of a surface acoustic wave sensor through a silanization reaction with 3‐glycidoxypropyltrimethoxysilane. The interactive selectivity of the silane surface for adsorption of several vapor analytes was measured using a gas chromatograph‐acoustic wave device combination. Much larger responses are obtained for compounds containing a nitrofunctional group. Computational chemistry is employed to calculate interaction energies for purported hydrogen‐bond complexes between analyte molecules and ethylene glycol, an analogue of the surface silane species. The results of these calculations are compared to the experimental sensor responses.
Plasticized PVC as a high efficiency selective barrier for the amperometric detection of phenolics
Authors: Christie Ian M. , Treloar Paul , Reddy Subrayal , Hepburn Carlos , Hulme John , Vadgama Pankaj
Published: May 2005

Ion selective and amperometric electrodes based on PVC membranes were constructed for the measurement of phenolics and assessed for potential use in monitoring coke works effluent treatment. Potentiometric working ranges are restricted to >100 mM, suffering thiocyanate interference, despite response slopes of <160mV/decade. Fabrication of a planar format is described, suitable for mass production. Similar membranes have been characterized in amperometric sensors, achieving greater sensitivity (>0.1 mM), tailored linear ranges and elimination of thiocyanate interference. Enhancement of electrochemical responses by use of high (>13) pH is achieved by stable encapsulation of such an environment beneath ion impermeable PVC within the sensor structure.
Humidity and temperature effects on the response to ethylene of an amperometric sensor utilizing a gold‐nafion electrode
Authors: Jordan Larry R. , Hauser Peter C. , Dawson George A.
Published: May 2005

The response to ethylene of chemically deposited gold‐Nafion electrodes was found to increase as the real surface area of the electrode was increased. However, humidity was found to lower the sensitivity of the electrode to ethylene. For larger electrode surface areas the humidity dependence of the sensor response to ethylene was found to increase. As well as the surface area, the method used to fabricate the gold‐Nafion electrode strongly influenced the humidity dependence. The response to ethylene on a vapor deposited electrode showed only a negligible humidity influence which may make this method more suitable for the fabrication of electrodes. The temperature dependence, for both chemically and vapor deposited electrodes, was found to be a 1% decrease in response to ethylene per °C decrease in temperature.
Indirect determination of ephedrine in urine by differential pulse polarography
Authors: Hernandez L. , Zapardiel A. , Bermejo E. , Perez J. A. , Chicharro M. , Garijo M. J.
Published: May 2005

The nitrosation of ephedrine and the electrochemical reduction of N‐nitrosoephedrine were investigated by differential pulse polarography and have been optimized in order to attain the optimum analytical signal. Reduction of the N‐nitrosoephedrine was carried out in one irreversible, diffusion‐controlled step using potassium chloride‐hydrochloric acid. In 0.1 M hydrochloric acid the N‐nitrosoephedrine shows a well‐defined reduction peak at −0.77 V (vs. Ag/AgCl/ 3 M KCl). An indirect differential‐pulse polarographic method is described for the determination of ephedrine at levels higher than 2.5 μg per mL of urine. An extraction procedure with C18 cartridge and a fast and easy nitrosation reaction with sodium nitrite in 0.2 M phthalate potassium hydrogen is also described. Determination of 5 μg/mL of N‐nitrosoephedrine in urine samples of 4 mL was possible using the standard addition method, with a relative error of −4.0% and relative standard deviations no higher than 2.1%.
Amperometric sensor for fish freshness based on immobilized multi‐enzyme modified electrode
Authors: Hu Shengshui , Liu Chung‐Chiun
Published: May 2005

An amperometric biosensor for the determination of fish freshness has been developed by immobilizing 5′‐nucleotidase (NT), nucleoside phosphorylase (NP) and xanthine oxidase (XO) enzymes on a Nafion‐paraquat chemically modified glassy‐carbon working electrode. The sensing principle is based on the oxygen consumption in the enzymatic reaction catalyzed by xanthine oxidase immobilized in the matrix. The quantity of hypoxanthine (Hx), the combined amount of inosine (HxR) and Hx and the total quantity of inosine 5′‐monophosphate (IMP), HxR and Hx can be determined, respectively, by changing the medium conditions. This sensor system can be used to determine the freshness of fish. An indicator of fish freshness, K1, is defined as K1 = {[HxR] + [Hx]}/{[IMP] + [HxR] + [Hx]}. This biosensor prowides a reliable means for determining of Hx, HxR and IMP in fish samples and the freshness of the fish meat.
Electrochemistry of hexacoordinate silicon(IV) porphyrin complexes
Authors: Lorenz Carrie R. , Dewald Howard D. , Lemke Frederick R.
Published: May 2005

Cyclic voltammetry was used to characterize the oxidation‐reduction behavior of a series of novel hexacoordinate silicon(IV) porphyrin complexes. Each (Por)SiX2 [Por = the dianions of the porphyrins: tetrakis(p‐tolyl)porphyrin (TTP), tetraphenylporphyrin (TPP), tetrakis(p‐trifluoromethylphenyl)porphyrin (TTFP), octaethylporphyrin (OEP), × = F, Cl, O3SCF3] complex undergoes one to two oxidations and one to two reductions, all occurring at the porphyrin ring. No silicon(IV) reduction is observed for any of the porphyrin complexes. The effects of solvent, supporting electrolyte, substituents on the porphyrin ring, axial ligands, certral metal, and ruffling of the porphyrin ring are described.
Electrochemical detection of disodium 3,3′‐azobis‐(6‐hydroxy‐) benzoate (olsalazine sodium)
Authors: Eriksson Alf , Nyholm Leif
Published: May 2005

Electrochemical detection of disodium 3,3′‐azobis‐(6‐hydroxy‐)benzoate, olsalazine sodium, in reversed phase liquid chromatography is shown to provide a detection limit of 40 fmol and a linear range extending up to 4 nmol for an injection volume of 20 μL. The method has been used for the determination of the solubility of olsalazine sodium in aqueous solutions. The solubility was found to be 2 × 10−8 M and 4 × 10−6 M at pH 1.0 and 3.5, respectively.
Voltammetric study of kinetin in a carbon fiber microelectrode. Determination by adsorptive stripping in apple extracts
Authors: Hernández Pedro , Patón Fernando , Hernández Lucas
Published: May 2005

This article presents an electroanalytical method of kinetin analysis using a carbon fiber microelectrode. Kinetin is one of the growth regulators in plants and belongs to the group of cytokinins. The adsorption process of the hormone to the microelectrode surface, previously subjected to electrochemical activation, permits a high degree of sensitivity in the quantification of kinetin in plant extracts.
A glucose amperometric sensor based on covalent immobilization of glucose oxidase in poly‐2‐aminoaniline film via chloranil on platinized platinum electrode
Authors: Losada José , Armada M. Pilar García
Published: May 2005

The construction and response of the immobilized enzyme chemically modified electrode as an amperometric sensor is described. Glucose oxidase (GOx) has been covalently bound to poly‐2‐aminoaniline (PAANI) film, formed onto a platinized Pt surface via a tetrachloro‐1,4‐p‐benzoquinone linkage. The steady‐state amperometric response of the sensor is investigated as a function of the glucose concentration, applied potential and platinum loading. The working potential for glucose determinations was +250mV (vs. SCE) and the biosensor exhibited a linear response in the range 0.2–20 mM with a response time that does not exceed 5 s.
Electrochemical quartz crystal microbalance study of the electrochemical behavior of riboflavin at gold electrodes
Authors: Wang Ying , Xu Bo , Zhu Guoyi , Wang Erkang
Published: May 2005

The electrochemical and adsorption behaviors of riboflavin (RF) at gold electrodes has been studied by using an electrochemical quartz crystal microbalance (EQCM). Useful information is obtained not only about electrochemical behavior but also about mass changes on the electrode surface. The electrochemical properties and frequency shifts were investigated in RF solutions at different pH values, concentrations and scan rates. Reversible voltammograms were observed for pH ⩽ 9.71. There was no electrochemical reaction for pH > 9.71. The maximum current response was obtained at about pH 8. The current response was proportional to the square root of scan rates when the concentration of RF was lower than 1.0 × 10−4 molL−1 (pH 6.92). On the contrary, at concentrations higher than 1.0 × 10−4 mol L−1 (pH 6.92), it was proportional to the scan rates.
Potentiometry with perchlorate and fluoroborate ion‐selective carbon paste electrodes
Authors: Ježková Jitka , Musilová Jarmila , Vytřas Karel
Published: May 2005

Perchlorate and tetrafluoroborate ion‐selective carbon paste electrodes based on different moditied pasting liquids were prepared and their basic characteristics were tested in direct potentiometric measurements. Although the slopes of calibration plots, detection limits as well as selectivity coefficients were similar to those obtained with commercial liquid/plastic membrane type ion‐selective electrodes, the carbon pastes offered some advantages as more rapid response and very low ohmic resistance. The resulting electrodes were successfully applied in ion‐pair formation‐based potentiometric titrations of perchlorate, fluororate and iodide ions with cetylpyridinium chloride.
Selective effects of aniracetam across receptor types and forms of synaptic facilitation in hippocampus
Authors: Xiao Peng , Staubli Ursula , Kessler Markus , Lynch Gary
Published: May 2005

Aniracetam reversibly increased synaptic responses mediated by the AMPA but not the NMDA subclass of glutamate receptors in hippocampus and was considerably more potent than structurally similar nootropics. The drug had greater effects on field excitatory postsynaptic potentials (EPSPs) in the dentate gyrus and CA1 region than it did in the CA3 region, suggesting that it differentiates between variants of the AMPA receptor. Ligand binding to glutamate receptors in synaptosomal membrane fractions was minimally changed by aniracetam. Finally, the percent facilitation produced by aniracetam in the CA1 region was not reduced by any of three treatments (4‐aminopyridine, changes in extracellular calcium concentrations, paired‐pulse stimulation) that affect release but, in accord with a previous report, was substantially decreased by long‐term potentiation. These results support the conclusion that aniracetam selectively increases the conductance of a subgroup of synaptic AMPA receptors in hippocampus and suggest that receptor changes underlie the expression of long‐term potentiation.
Linear relationship between the maintenance of hippocampal long‐term potentiation and retention of an associative memory
Authors: Doyère Valérie , Laroche Serge
Published: May 2005

The hypothesis that the maintenance or decay of an associative memory trace after an extended retention interval is a function of the residual strength of the synapses originally strengthened during learning was examined in a classical conditioning paradigm in which high‐frequency stimulation of a hippocampal input—the medial perforant path—served as a conditioned stimulus. Rats received perforant path stimulus‐foot shock pairings while engaged in a previously acquired food‐motivated lever‐pressing task. Conditioned suppression of lever pressing was the behavioral measure of learning and retention of the association. Stimulus trains to the perforant path at an intensity above the threshold for eliciting a population spike induced long‐term potentiation of synaptic transmission in the dentate gyrus. Synaptic potentials recorded extracellularly in the dentate gyrus were subsequently monitored for 31 days to examine quantitatively the decay of synaptic potentiation, a period after which retention of the learned association was assessed. All rats learned the association to a similar extent and displayed equivalent amounts of long‐term potentiation by the end of conditioning. A slowly decaying function of synaptic potentiation was observed in remembering rats, i. e., rats with high retention performance after the 31‐day learning‐to‐retention interval, while forgetting was associated with a rapid decay of long‐term potentiation. Behavioral performance at the long‐term memory test was linearly correlated with the amplitude of long‐term potentiation maintained just prior to the retention test. The results favor the hypothesis that long‐term associative memory depends, at least in part, on the maintenance of elevated synaptic strengths in the pathway activated during learning and suggest a role for the lasting component of long‐term potentiation in the maintenance of memory.
Bilateral knife cuts to the perforant path disrupt spatial learning in the Morris water maze
Authors: Skelton Ronald W. , McNamara Robert K.
Published: May 2005

Both the hippocampus and the entorhinal cortex are known to be crucial for spatial learning, but the contribution of the pathway linking the two structures, the perforant path (PP), has never been tested in a spatial learning paradigm. The present study examined the role of the PP in spatial learning using the Morris water maze. Seven days after bilateral transection of the PP with a fine‐bladed knife, rats were habituated to the pool, then trained to swim from varying start locations to a platform submerged in a fixed location. After 28 training trials over 5 days, probe trials (without any platform present) were given to assess spatial memory for the location. Compared to sham‐operated controls, lesioned rats showed slower learning and poorer asymptotic performance in terms of both swim path distance and escape latency, and less preference for the correct quadrant during probe trials. When the platform location was “reversed” to the opposite quadrant, the lesioned rats again showed poorer learning, poorer asymptotic performance, and reduced preference for the correct quadrant on the probe trial. When tested with a visible platform whose position varied from trial to trial, lesioned rats performed as well as controls. These results are congruent with previous analyses of the contributions of the entorhinal cortex and hippocampus to spatial learning and suggest that for spatial learning, the PP is a critical functional link between these two structures.
Fast (beta) rhythms in the hippocampus: A review
Authors: Leung L. Stan
Published: May 2005

Spontaneous or evoked brain activity in the hippocampus showed a 20–70 Hz beta rhythm under some conditions, typically during behavioral activation and accompanied by a theta rhythm. Beta rhythms are generated locally, perhaps by a recurrent feedback loop involving pyramidal cells and inhibitory interneurons. Modulation of the local circuit and rhythm by cholinergic inputs has also been demonstrated. Under some behavioral states, neural impulses modulated at the beta frequency may transmit preferentially through the trisynaptic circuit in the hippocampus. It is suggested that the beta rhythm may serve to establish transient physiological connections, reflected in coherence at the beta frequency, among neurons in the hippocampus and related structures. Thus, the beta rhythm may play an essential role in hippocampal function.
Maintained saturation of hippocampal long‐term potentiation does not disrupt acquisition of the eight‐arm radial maze
Authors: Robinson Gilbert B.
Published: May 2005

The present experiment examined the anterograde effect of bilateral saturation of long‐term potentiation (LTP) of the rat perforant path‐granule cell response on acquisition of the eight‐arm radial maze. To ensure maintained saturation, high‐frequency stimulation was applied to the perforant path immediately prior to each trial. LTP did not significantly increase the number of trials required for acquisition of the standard eight‐arm radial maze task. Furthermore, the magnitude of LTP did not correlate with the rate of acquisition. LTP also did not significantly affect the number of either working or reference memory errors during subsequent training with only four of the eight arms baited; both control and LTP rats made significantly more reference memory than working memory errors, with the number of both types of errors decreasing as training progressed. These results indicate that prior saturation of LTP within the perforant path‐dentate granule cell circuit does not affect acquisition of either the reference or working memory components of the radial maze task. The results are discussed in relation to the role of LTP in acquisition of the eight‐arm radial maze.
Structural synaptic plasticity associated with the induction of long‐term potentiation is preserved in the dentate gyrus of aged rats
Authors: Geinisman Yuri , de Toledo‐Morrell Leyla , Morrell Frank , Persina Inna S. , Rossi Marvin
Published: May 2005

Changes in synaptic numbers were examined in the hippocampal dentate gyrus of aged (28 months old) rats following the induction of long‐term potentiation (LTP) by high‐frequency stimulation of the medial perforant path carried out on each of 4 consecutive days. Potentiated animals were sacrificed 1 hour after the fourth stimulation. Stimulated but not potentiated and implanted but not stimulated rats of the same chronological age served as controls. Synapses were analyzed in the middle (MML) and inner (IML) molecular layer of the dentate gyrus. Using the stereological dissector technique, unbiased estimates of the number per neuron were obtained for the following morphological varieties of synapses: axodendritic synaptic junctions involving dendritic shafts, nonperforated axospinous synapses having a continuous postsynaptic density (PSD), and perforated ones distinguished by a fenestrated, horseshoe‐shaped, or segmented PSD. The induction of LTP resulted in a selective increase in the number of synapses with segmented PSDs. This change was detected only in the potentiated synaptic field (MML), but not in an immediately adjacent one (IML), which was not directly stimulated during the induction of LTP. Comparison of these data with the results of our previous LTP study in young adult rats (Geinisman, Y. et al., 1991, Brain Res. 566:77–88) showed that the only significant difference in the absolute number of synaptic contacts per neuron between potentiated animals of the two chronological ages was an age‐related reduction in segmented synapses of the MML. Relative increases in the number of segmented synapses per neuron were, however, virtually of the same magnitude in potentiated rats of both ages as compared with their respective controls. This finding may explain why senescent rats can be potentiated to the same extent as young ones.
Hippocampal morphology and spatially related behavior in long‐evans and CFY rats
Authors: Schwegler Herbert , Mueller Gary G. , Crusio Wim E. , Szemes Laszlo , Seress Laszlo
Published: May 2005

Behavioral responses to novelty in an open field and spatial learning in a radial maze with four arms out of eight reinforced were tested in male and female CFY and Long‐Evans rats. Subsequently, the sizes of the total hippocampi and of various hippocampal cell layers and terminal fields at the midseptotemporal level were measured in Timm‐stained sections. No strain differences were found in the open field (except for defecation). In the radial maze, Long‐Evans rats showed better spatial reference memory capabilities than rats of the CFY strain. The relative sizes of the intra‐ and infrapyramidal mossy fiber (IIP‐MF) projections did not differ between the strains. Within the more variable CFY strain, a positive correlation between the size of the IIPMF projection and radial maze performance was found. The absolute sizes of the entire hippocampi and all hippocampal layers at the midseptotemporal level were larger in the CFY strain. The size of the suprapyramidal mossy fiber projection was related to the number of granule cells and to the ratio between granule and CA3 pyramidal cells. In contrast, the size of the IIP‐MF projection did not correlate with either of these variables. The results indicate that the size of the mossy fiber projection may be determined mainly by the available postsynaptic surface on the dendrites of CA3 pyramidal neurons. Furthermore, an increased number of granule cells and their larger projection to the apical dendrites of pyramidal neurons does not appear to result in physiological changes with behavioral consequences. The results also indicate that hippocampal size or the numbers of hippocampal neurons as shown in particular bird and rodent populations is not an indicator of spatial learning capacity in commonly used laboratory rodent strains.
Adenosine‐induced suppression of synaptic responses and the initiation and expression of long‐term potentiation in the CA1 region of the hippocampus
Authors: Mitchell John B. , Miller Karen , Dunwiddie Thomas V.
Published: May 2005

The results of several previous studies have suggested that pretreatment with adenosine can block the induction of long‐term potentiation (LTP), although other studies have found no effect of adenosine on the induction of LTP. The interaction of adenosine with the induction of LTP in the rat hippocampal slice was investigated. Inhibition of synaptic responses by adenosine either prior to or immediately after high‐frequency or theta‐burst stimulation did not affect LTP measured after washout of the adenosine. The only conditions under which adenosine blocked the development of LTP was when it was given 3–5 minutes prior to the stimulation train. To understand how it was possible to induce LTP, during the period 1–3 minutes following adenosine when synaptic responses were virtually eliminated, evoked responses during the 100 Hz stimulation train were recorded. Although synaptic responses to low‐frequency stimulation were virtually eliminated by adenosine, they reappeared during high‐frequency stimulation. These results suggest that although adenosine can depress synaptic responses, an increase in neurotransmission during a high‐frequency train can partially overcome this effect of adenosine, and the hypothesis that adenosine can selectively block LTP is not supported.
Induction of long‐term potentiation at perforant path dentate synapses does not affect place learning or memory
Authors: Sutherland Robert J. , Dringenberg Hans C. , Hoesing Janice M.
Published: May 2005

In two experiments the authors failed to detect an effect of inducing bilateral, long‐lasting synaptic potentiation at perforant path dentate synapses on spatial learning by rats in the Morris place navigation task. Daily sessions of high‐frequency stimulation of perforant path axons produced large increases to an asymptotic level in population spike and field excitatory postsynaptic potential recorded in ipsilateral dentate gyrus. Place learning proceeded normally 24 hours after the last of 14 high‐frequency stimulation sessions in rats that had previously mastered the procedural aspects of place navigation (Experiment 1) and in rats that were naive (Experiment 2).
Transduction of a protein kinase C‐generated signal into the long‐lasting facilitation of glutamate release
Authors: Terrian David M. , Ways D. Kirk , Gannon Robert L. , Zetts Debbie A.
Published: May 2005

The present study investigated the delayed and persistent effects of 4β‐phorbol 12, 13‐dibutyrate (PDBu) on the K+ ‐evoked release of endogenous glutamate and dynorphin B‐like immunoreactivity from a subcellular fraction (P3) that is enriched in hippocampal mossy fiber synaptosomes. It is demonstrated that the alpha, beta, gamma, epsilon, and zeta isoforms of protein kinase C (PKC) are present in the P3 fraction obtained using the guinea pig hippocampus as starting tissue. The K+ ‐evoked release of glutamate was found to be selectively enhanced when mossy fiber‐enriched synaptosomes were preincubated with PDBu for 15 minutes and extensively washed with a PDBu‐free medium. The persistent enhancement of glutamate release observed under this condition was not reversed by the protein kinase inhibitor staurosporine and was desensitized to the potentiating effects of an acute reexposure to PDBu. The overall content and activity of PKC was not substantially altered during the initial 15 minutes of treatment with PDBu (10 μM). More prolonged pretreatments with PDBu altered the substrate specificity of PKC and decreased the content of all PKC isoforms, but did not reverse the facilitation of glutamate release that followed preincubation in the presence of PDBu. It is concluded that the persistent activation of PKC enhances K+ ‐evoked glutamate release from hippocampal mossy fiber‐enriched synaptosomes and that, once established, this presynaptic facilitation is sustained by a process that is no longer directly dependent on continued PKC phosphotransferase activity.
Hippocampus minor and man's place in nature: A case study in the social construction of neuroanatomy
Authors: Gross Charles G.
Published: May 2005

In mid‐19th century Britain the possibility of evolution and particularly the evolution of man from apes was vigorously contested. Among the leading antievolutionists was the celebrated anatomist and paleontologist Richard Owen and among the leading defenders of evolution was Thomas Henry Huxley. The central dispute between them on human evolution was whethe or not man's brain was fundamentally unique in having a hippocampus minor (known today as the calcar avis), a posterior horn in the lateral ventricle, and a posterior lobe. The author considers the background of this controversy, the origin and fate of the term hippocampus minor, why this structure became central to the question of human evolution, and how Huxley used it to support both Darwinism and the political ascendancy of Darwinians. The use of ventricular structures to distinguish humans from other animals appears to reflect an importance given to the ventricles that stretches back to ancient Greek medicine. This account illustrates both the extraordinary persistence of ideas in biology and the role of the political and social matrix in the study of the brain.
Hippocampal theta rhythm in behaving rats following ibotenic acid lesion of the septum
Authors: Leung L. Stan , Martin Lee‐Anne , Stewart Dwight J.
Published: May 2005

The effects of ibotenic acid lesion of the septum were studied in rats implanted with chronically indwelling electrodes and septal cannula. Each rat served as its own control and the properties of the hippocampal theta rhythm were studied before and after ibotenic acid and control saline infusion into the medial septal area. Ibotenic acid preferentially killed neurons in the lateral septum, and significantly attenuated the hippocampal theta rhythm about 50% bilaterally, at both surface and deep electrodes. The coherence and the phase of the theta rhythm at the CA1 apical dendrites, with respect to a superficial electrode, also declined significantly after ibotenic acid lesion. Pilocarpine (25 mg/kg i. p.) induced a theta rhythm of 7–9 Hz during immobility in the lesioned rats that was significantly higher in frequency than that induced in intact rats (4–6 Hz). In lesioned rats, the theta rhythm during tail pinch under urethane anesthesia was largely abolished, and the theta during walking was attenuated by atropine sulfate (50 mg/kg i. p.). Phencyclidine (10 mg/kg i. p.) or parachlorophenylaline (PCPA) alone, which was inferred to abolish an atropine‐resistant theta input, did not affect the power of the walking theta rhythm in either the lesioned or the normal rat. It was concluded that the theta in the behaving rats after ibotenic acid lesion in the septum has a strong astropine‐sensitive component, and that it is not predominantly atropine‐resistant, as suggested previously. The lack of PCPA effect on the theta phase in intact and lesioned rats also suggested a different view of the atropine‐resistant theta in hippocampal region CA1. One possible mechanism of the atropine‐resistant theta at the distal dendrites of pyramidal cells may result from rhythmic inhibition by stratum lacunosum‐moleculare interneurons which may be activated by either serotonergic or cholinergic inputs. © 1994 Wiley‐Liss, Inc.
Somatostatin‐containing neurons in rat organotypic hippocampal slice cultures: Light and electron microscopic immunocytochemistry
Authors: Kunkel Dennis D. , Nguyen Loan B. , Harrigan Mark R. , Schwartzkroin Philip A. , Malouf Alfred T.
Published: May 2005

Light and electron microscopic immunocytochemical techniques were used to study the interneuron population staining for somatostain (SRIF) in cultured slices of rat hippocampus. The SRIF immunoreactive somata were most dense in stratum oriens of areas CA1 and CA3, and in the dentate hilus. Somatostain immunoreactive cells in areas CA1 and CA3 were characteristically fusiform in shape, with dendrites that extended both parallel to and into the alveus. The axonal plexus in areas CA1 and CA3 was most dense in stratum lacunosum‐moleculare and in stratum pyramidale. Electron microscopic analysis of this area revealed that the largest number of symmetric synaptic contacts from SRIF immunoreactive axons were onto pyramidal cell somata and onto dendrites in stratum lacunosum‐moleculare. In the dentate gyrus, SRIF somata and dendrites were localized in the hilus. Hilar SRIF immunoreactive neurons were fusiform in shape and similar in size to those seen in CA1 and CA3. Axon collaterals coursed throughout the hilus, projected between the granule cells and into the outer molecular layer. The highest number of SRIF synaptic contacts in the dentate gyrus were seen on granule cell dendrites in the outer molecular layer. Synaptic contacts were also observed on hilar neurons and granule cell somata. SRIF synaptic profiles were seen on somata and dendrites of interneurons in all regions. The morphology and synaptic connectivity of SRIF neurons in hippocampal slice cultures appeared generally similar to intact hippocampus. © 1994 Wiley‐Liss, Inc.
Dopamine D2 receptor expression in hippocampus and parahippocampal cortex of rat, cat, and human in relation to tyrosine hydroxylase‐immunoreactive fibers
Authors: Goldsmith Sara K. , Joyce Jeffrey N.
Published: May 2005

A detailed study comparing the distribution of D2 receptors and tyrosine hydroxylase‐immunoreactive fibers in the hippocampus and parahippocampal cortices of the rat, cat, and human was conducted. The distribution of [125I]epidepride binding to D2 receptors along the transverse and longitudinal axes of the hippocampus and parahippocampus differed among the species. In rat hippocampus, the number of sites was highest in septal portions of lacunosum‐moleculare of CA1 and stratum moleculare of the subiculum. Virtually no binding to D2 receptors existed in the temporal hippocamps. For the cat hippocampus, the highest binding existed in the inner one‐third of the molecular layer of the dentate gyrus (DG). There were also significant numbers of D2 receptors in strata radiatum and oriens of the CA subfields, with almost undetectable levels in lacunosum moleculare and subiculum. The number of sites was higher in the septal than temporal hippocampus. In the human hippocampus, highest binding was observed in the molecular layer of DG and the subiculum, with lower levels in strata oriens and lacunosum‐moleculare of CA3, and very low binding in CA1. The histochemical demonstration of the pattern of mossy fibers revealed an organization complementary to that of D2 receptors in cat and human. In none of the species was there significant expression of D2 receptors in the entorhinal cortex, except in the caudal extreme of this region in the rat. In that region a trilaminar pattern was exhibited that continued into the perirhinal cortex. A trilaminar pattern of D2 receptor expression was observed in the perirhinal cortex of all species, with the highest values in the external and deep laminae and low expression in the middle laminae. The organization of dopamine fibers was assessed by comparing the distribution of tyrosine hydroxylase‐positive and dopamine β‐hydroxylase‐immunoreactive fibers in these same regions. It revealed consistent mismatches between the pattern of D2 receptor expression and dopaminergic innervation in all three species. The implications for this mismatch are discussed. It is hypothesized that the distribution of D2 receptors, and not of dopamine fibers, determines what neural systems dopamine influences in the hippocampal complex. © 1994 Wiley‐Liss, Inc.
Maturation of long‐term potentiation in the hippocampal dentate gyrus of the freely moving rat
Authors: Bronzino Joseph D. , Abu‐Hasaballah Khamis , Austin‐LaFrance Robert J. , Morgane Peter J.
Published: May 2005

The ability of the perforant path/dentate granule cell synapse of the hippocampal formation to establish and maintain enhanced levels of synaptic transmission in response to tetanization (long‐term potentiation, LTP) was investigated in freely moving rats at 15, 30, and 90 days of age. Measures of (1) the slope of the population excitatory postsynaptic potential (EPSP), and (2) the population spike amplitude (PSA) obtained before, and at several times following tetanization, were used to evaluate the magnitude and duration of LTP as a function of age. Significant enhancement of both EPSP slope and PSA measures was obtained from animals of all three ages in response to perforant path tetanization. The initial degree of enhancement was essentially the same across the age groups, ranging from +27% to +38% of pretetanization levels for EPSP slope measures and +60% to +75% of pretetanization levels for PSA measures, obtained 15 min after tetanization. The duration of this enhancement obtained from animals of the preweaning group was significantly longer than that obtained from either 30‐ or 90‐day‐old animals. Enhanced measures of both EPSP slope and PSA decayed to baseline levels in these older animals 18 to 24 h after tetanization, while animals tetanized at 15 days of age maintained potentiated levels of both measures for a period of 5 days following tetanization. Tetanization of 15‐day‐old animals resulted in a significant reduction in the latency to EPSP onset without affecting the time‐based relationships among the other measured parameters, which included latency of the population spike onset, population spike minimum, and population spike offset. Tetanization had no effect on the latency measure of any of these parameters in either of the two older age groups. The primarily postnatal development of the dentate granule cell population suggests that both functionally immature GABAergic modulation of granule cell activity and the differential development of components of the N‐methyl‐D‐aspartate receptor complex may be involved in the age‐related differences in the induction and expression of the LTP phenomenon. This study represents the first developmental characterization of LTP in the perforant path/dentate granule cell synapse in freely moving rats during early development. The results indicate that LTP can be reliably established and maintained in behaving rats as young as 15 days of age. Whereas the degree of potentiation at this age is equivalent to that obtained from juveniles and young adults, the duration of the effect significantly outlasts that obtained from older animals in which development of the dentate gyrus is more functionally mature. © 1994 Wiley‐Liss, Inc.
Localization of mRNAs encoding two forms of glutamic acid decarboxylase in the rat hippocampal formation
Authors: Houser Carolyn R. , Esclapez Monique
Published: May 2005

The mRNAs for two forms of glutamic acid decarboxylase (GAD65 and GAD67) were localized in the rat hippocampal formation by nonradioactive in situ hybridization methods with digoxigeninlabeled cRNA probes. Some neurons in all layers of the hippocampus and dentate gyrus were readily labeled for each GAD mRNA, and the patterns of labeling for GAD65 and GAD67 mRNAs were very similar. All major groups of previously described GAD‐and GABA‐containing neurons appeared to be labeled for each GAD mRNA. Such findings suggest that most GABA neurons in the hippocampal formation contain both GAD mRNAs. When the labeling of neurons in the hippocampal formation and cerebral cortex was compared in the same sections, the intensity of neuronal labeling for GAD67 mRNA was generally similar in the two regions. However, the intensity of labeling for GAD65 mRNA was generally stronger for many neurons in the hippocampal formation than for most neurons in the cerebral cortex. Neurons in the hilus of the dentate gyrus were particularly well labeled for GAD65.

The nonradioactive labeling for the GAD mRNAs was confined to the cytoplasm of neuronal cell bodies, and this allowed a clear visualization of the relative number and location of labeled neurons. Several distinct patterns of GAD mRNA‐containing neurons were observed among different regions of the hippocampal formation. In the hilus of the dentate gyrus, GAD mRNA‐containing neurons were numerous in the regions deep to the granule cell layer as well as in more central parts of the hilus. Within CA3, the densities (quantities) of labeled neurons varied among the regions. In the inner or hilar segment of CA3, the density of labeled neurons was often lower than that in the outer part of CA3 where numerous labeled neurons were distributed throughout all layers. In CA1, GAD mRNA‐labeled neurons were distributed in a relatively laminar pattern with the highest density in stratum pyramidale and moderate densities in stratum oriens and at the interface between strata radiatum and lacunosum‐moleculare. Lower densities were found within the latter two layers.

The prominent localization of the two GAD mRNAs in the hippocampal formation suggests that dual system for GABA synthesis is necessary for normal GABAergic function in this brain region. Most putative GABA neurons contain relatively high levels of GAD67 mRNA as might be expected if this GAD form is responsible for the synthesis of GABA for metabolic and baseline synaptic function. The relatively high levels of GAD65 mRNA in many hippocampal neurons, particularly those of the dentate hilus, may indicate that these neurons have a well‐developed reserve system for GAD and GABA synthesis. © 1994 Wiley‐Liss, Inc.
Ultrastructural identification of entorhinal cortical synapses in CA1 stratum lacunosum‐moleculare of the rat
Authors: Desmond Nancy L. , Scott Carol A. , Jane John A. , Levy William B.
Published: May 2005

The goal of the present study was to identify and characterize, at the electron microscopic level, the synapses formed by entorhinal cortical (EC) axons in the hippocampal CA1 stratum lacunosummoleculare of the adult rat. Phaseolus vulgaris leucoagglutinin was ionotophoresed at various loci throughout the mediolateral and dorsoventral extent of the EC to label EC‐CA1 synapses. Virtually all labeled synapses were asymmetric and axospinous. EC axons did not preferentially synapse with any particular type of dendritic spine; rather, EC axons formed synapses with the range of dendritic spine morphologies observed in CA1 s. lacunosum‐moleculare. Spines with either perforated or nonperforated postsynaptic densities were contacted by EC axons. Occasionally both a labeled and an unlabeled axon synapsed on a single dendritic spine head. The data are discussed in relation to the morphology of other afferent systems synapsing in s. lacunosum‐moleculare and to the physiology of the EC‐CA1 system. © 1994 Wiley‐Liss, Inc.