bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of thiamine antagonists on nerve conduction. I. Actions of antimetabolites and fern extract on propagated action potentials
Authors: Goldberg Daniel J. , Cooper Jack R. 
Published: January 2005

AbstractTo assess the hypothesis that thiamine is directly involved in the permeability changes at the sodium channel during nerve conduction, the effects of thiamine antagonists on lobster giant axon resting and action potentials were determined. Thiamine antimetabolites, in millimolar concentrations, reversibly decreased the maximum rate of rise and amplitude of the action potential while increasing its duration. In particular, thiamine tert‐butyl disulfide (TTBD) elicited the formation of pronounced shoulders during repolarization, lengthening the action potential by 2–50 times, depending on dose. Antimetabolites also depolarized the resting membrane, but this change was poorly reversible and may indicate a dual mechanism for antimetabolite action. An extract of the fern, Pteris aquilina, reversibly decreased the maximum rate of rise of the action potential and depolarized the resting potential. It also elevated and prolonged the action potential after‐depolarization, sometimes causing repetitive activity. The strength of these actions was correlated with the antithiamine potency of the extract, and was diminished by addition of thiamine to the extract.
Effects of anisomycin on brain protein synthesis and passive avoidance learning in newborn chicks
Authors: Bull R. , Ferrera E. , Orrego F. 
Published: January 2005

AbstractThe effects of anisomycin (ANM) on newborn chicks have been studied with respect to brain protein synthesis, growth, EEG, toxicity, and several passive avoidance learning tasks. It was found that intracerebral ANM (80 nmol) gave a maximum inhibition of brain protein synthesis of 30%, while a combination of subcutaneous (10 μmol; 53 mg/kg) plus intracerebral (80 nmol; 21 μg) ANM, inhibited by 91% in the first 2 hr and by 75% in the subsequent 2 hr period. Cycloheximide (CXM) also in combined injections at the same doses as ANM, inhibited by 97% in the 4 hr that followed injection. However, all the CXM‐injected chicks were dead by 18 hr, while the lethality of ANM did not differ from that of saline. ANM also did not affect EEG measured at 1, 3, 5, or 24 hr following the subcutaneous plus intracerebral injections, nor did ANM affect body or brain growth curves or brain protein accretion.In the learning experiments, animals were initially trained to peck at water‐coated metal spheres (type A learning) or at water‐imbibed birdseed (types B and C learning) in less than 1 sec, and were exposed to the same lures treated with the aversant methylanthranilate (MeA) one day later on one occasion (types A and B learning) or exposed twice (type C learning) and tested for learning retention one day later. Learning criterion was set as failure to peck at the lure during the first 20 sec of presentation. If ANM was injected 1 hr prior to MeA exposure, large and highly significant memory deficits were found during the retention test, as compared with saline injected controls. No effect of ANM was seen, however, if it was injected one day after learning, indicating that it did not interfere with retrieval mechanisms. ANM also decreased the external manifestations of fear or displeasure that chicks express during retention testing. Such manifestations have a high correlation with pecking suppression (r = 0.88, P < 0.001).
Effects of denervation and colchicine treatment on the chloride conductance of rat skeletal muscle fibers
Authors: Camerino D. , Bryant S. H. 
Published: January 2005

AbstractMembrane potentials, cable parameters, and component resting conductances were measured in extensor digitorum longus (EDL) muscle fibers from adult rats in vitro at 24°C, after 15 to 18 days of denervation by nerve section, and at seven to ten days following epineural injection of 100 to 450 μg of colchicine in the peroneal nerve. The denervated muscles were paralyzed throughout the experimental period, whereas the colchicine‐treated preparations showed no clinical paralysis except for the first day or two. The EDL from the untreated side served as a control.Both the denervated and colchicine‐treated fibers were depolarized, showed signs of fibrillation, had tetrodotoxin‐resistant action potentials, and membrane resistance was increased two‐ to sevenfold. In the denervated fibers, mean chloride conductance GCl dropped from a control value of 3196 to 596 μmhos/cm2 while mean potassium conductance GK showed a tendency to rise from 260 to 332 μmhos/cm2. Colchicine‐treated fibers while showing a similar fall in mean GCl from 2993 to 1066 μmhos/cm2, also showed a significant fall in mean GK from 213 to 116 μmhos/cm2.It was concluded that factors transported by the microtubular system are important for the maintenance of the high resting GCl of mammalian skeletal muscle fibers.
The identification of two inhibitory cells in each segmental ganglion of the leech and studies on the ionic mechanism of the inhibitory junctional potentials produced by these cells
Authors: Sawada Masashi , Wilkinson Joyce M. , McAdoo David J. , Coggeshall Richard E. 
Published: January 2005

AbstractThe present study identifies a pair of inhibitory cells that are located on each anterolateral margin of a leech segmental ganglion. These cells, which we label as cells 119, are electrically interconnected. These cells give rise to inhibitory junctional potentials (ijp's) in contralateral longitudinal body wall muscle cells. The latencies of the ijp's following spikes in cell 119 are variable. The ijp's are caused by transient increases in premeability to the Cl− ion. Previous studies demonstrated that 5‐HT causes a hyperpolarization of body wall muscle cells by increasing the permeability of muscle membrane to the Cl− ion. Accordingly, 5‐HT was searched for in the 119 cell bodies, but autoradiography, fine structure, and gas chromatography‐mass spectrometry gave no indication that 5‐HT was present in these cells. However, the variable latencies of the ijp's may indicate that there is a neuron interposed between cell 119 and the muscle cells. If this is the case, then the interposed neuron should be analyzed for 5‐HT. Further experiments to locate the terminals of cells 119 and the cell bodies of the presumed interposed neurons are thus desirable.
A central inhibitory action of 5‐hydroxytryptamine in the leech
Authors: Sawada Masashi , Coggeshall Richard E. 
Published: January 2005

AbstractPrevious studies indicated that 5‐HT reduced the number of spontaneous excitatory junctional potentials (ejp's) that occurred in leech body wall muscle cells. The present study confirms these findings and shows that the ejp's arise from impulses in motoneuron L. This study further shows that 5‐HT acts by hyperpolarizing and reducing the membrane resistance of neuron L, thus inhibiting the motoneuron and reducing the frequency of spontaneous ejp's on body wall muscle cells. These effects of 5‐HT are not seen when the ganglion is bathed in a high magnesium solution, a finding that suggests that 5‐HT does not act directly on the membrane of motoneuron L. This study demonstrates that 5‐HT can have a central inhibitory effect on body wall muscle contractions. Previous studies provide evidence that 5‐HT may act as a direct neuromuscular inhibitory transmitter and may also take part in peripheral presynaptic inhibition. Thus, if further studies confirm these suggestions, the well‐known inhibitory effect of 5‐HT on leech body wall muscle is a more complex process than was previously thought.
Permeability of the endplate membrane activated by acetylcholine to some organic cations
Authors: Maeno Takashi , Edwards Charles , Anraku Mitsuo 
Published: January 2005

AbstractThe ability of various organic cations to depolarize the ACh‐activated endplate membrane in the absence of Na ions was examined on frog sartorius muscle by measuring the endplate potential on the muscle surface with the moving electrode technique. The ACh‐activated endplate membrane was very permeable to ammonium and its methyl and hydroxy derivatives, and moderately permeable to guanidine derivatives and Tris (hydroxymethyl) aminomethane. The permeability of alkylol derivatives of ammonium diminished progressively with increase in molecular size. The present results suggested that the endplate ionic channels can be represented by a pore of about 6.4 Å in diameter.
Neurophysiological mechanisms involved in photo‐entrainment of the circadian rhythm from the Aplysia eye
Authors: Eskin Arnold 
Published: January 2005

AbstractAn attempt was made to identify the neurophysiological processes involved in entrainment of the circadian rhythm of spontaneous optic nerve potentials from the Aplysia eye by determining whether pharmacological agents or ion substitutions could block phase shifts produced by single light pulses. Knowing which physiological processes are involved in entrainment should help define the morphological pathway traveled by entrainment information.A secretory step does not appear to be involved in the flow of entrainment information from the environment to the circadian oscillator. A treatment (HiMg LoCa) capable of inhibiting secretion did not interfere with phase shifting by light. Furthermore, treating eyes with putative transmitters or extracts of eyes did not phase shift the free running rhythm. Also, the phase shifting information is not translated into action potentials before reaching the oscillator since TTX–HiMg LoCa solutions did not block the light‐induced phase shift. The photoreceptor potential does seem to be important for light‐induced phase shifts. A correlation was found between the effects of treatments on the ERG and their effects on the light‐induced phase shift. Solutions which decreased the ERG by 90% or more blocked phase shifting whereas solutions which decreased the ERG by less than 74% had no effect on phase shifting by light.The results from these studies are consistent with two pathways for the flow of phase shifting information to the circadian oscillator. The circadian oscillator may be associated with receptor cells and the entrainment pathway would include a step involving the photoreceptor potential. Alternatively, the circadian oscillator may be associated with secondary cells and receive entrainment information via the photoreceptor potential and passive spread of current through a gap junction. Higher order cells than second‐order ones are probably not involved in the entrainment pathway.
Spreading depression elicited by thermal effects of ultrasonic irradiation of cerebral cortex in rats
Authors: Ueda M. , Bureš J. , Fischer J. 
Published: January 2005

AbstractCortical spreading depression (CSD) was elicited by focused ultrasonic irradiation (800 kHz) of exposed cerebral cortex in anesthetized rats. With the acoustic output of 0.65 W at the probe‐tissue contact (3 mm in diameter), CSD was elicited after 28‐sec irradiation in normothermic rats. Reduction of cortical temperature to 31°C increased the threshold irradiation time to 82 sec on the average. Ten‐ to thirty‐sec heating of cerebral cortex with a thermode elicited CSD when surface temperature exceeded 47°C. Histological examination of the cortical areas exposed to threshold irradiation revealed a central coagulation lesion surrounded by edema. It is concluded that the ultrasonic irradiation elicits CSD by dissipated heat. Differences in threshold duration of irradiation in hypothermic and normothermic rats were used to compute the threshold temperature which had to be exceeded in the critical volume of cortex in order to start CSD.
Excitation of the common inhibitory motor neuron: A possible role in the startle reflex of the cockroach, Periplaneta americana
Authors: Fourtner Charles R. , Drewes Charles D. 
Published: January 2005

AbstractThe responses of the widespread common inhibitory motor neuron (CI) to tactile stimulation of the cercus and the abdomen and electrical stimulation of the cercal nerve and the abdominal connectives are investigated. Tactile stimulation produces high frequency (>500 impulses/s) spike discharge in CI with the onset of CI activity preceding the discharge of the excitatory motor neurons. Electrical stimulation of the connectives demonstrates a monosynaptic connection between at least one intermediate sized fiber (conduction velocity = 3.7 m/s) in the abdominal connective and the ipsilateral CIs in the meso‐ and metathoracic ganglia. Electrical stimulation of the cercal nerve suggests a disynaptic path from cercal nerve to CI. Arguments are presented for a cercal afferent‐to‐CI reflex and the possible functional role of early excitation of CI is discussed.
Physiological characteristics and reflex activation of DUM (octopaminergic) neurons of locust metathoracic ganglion
Authors: Hoyle Graham , Dagan Dani 
Published: January 2005

AbstractIntracellular recordings were made from single or pairs of somata of the dorsal unpaired median (DUM) neurons of the metathoracic ganglion of the locust Schistocerca gregaria and the grasshopper Romalea microptera, during reflex actions, direct electric excitation and orthodromic and antidromic neural stimulation. Some, possibly all, of these neurons are unique, identifiable individuals in regard to their targets, which are specific peripheral muscles. Their physiological properties and the ways they are activated synaptically are, however, similar. Large, overshooting action potentials, comprising three components, occur. The first component in time is small and represents an excitatory synaptic potential for orthodromic stimulation or an axon spike (AS) for antidromic stimulation, electrotonically conducted into the soma. The second component is larger, being an electrotonically conducted integrating segment spike (ISS). The final component is the soma spike (SS). Neither AS nor ISS have a late positive phase, but there is a large, prolonged one for SS. The latter, combined with rapid accommodation, determine a low maximum firing rate for the neurons.Most nerves entering the ganglion make excitatory inputs onto each DUM neuron, which is readily driven to spike by electric excitation of either connective. There is a great deal of spontaneous excitatory synaptic input to each DUM neuron and a high proportion of it is common. Although there is no detectable electrical coupling between the cells, there is about 30% synchronous firing, apparently due to the common inputs; independent excitation and inhibition also occur. All sensory modalities tested have inputs to the neurons, which tend to fire constantly at a low rate (1 per 3–4 sec). In reflex actions, DUM neurons tend to fire before motor output occurs. It is suggested that the cells will be found to have many functions serving a general role comparable to that achieved by the release of adrenaline in vertebrates.
In vivo responses of paired giant mechanoreceptor neurons in Aplysia abdominal ganglion
Authors: Cobbs J. S. , Pinsker H. M. 
Published: January 2005

AbstractTwo neurons with cell bodies symmetrically located in the abdominal ganglion and giant axons in the left (L1) and right (R1) pleurovisceral connectives of Aplysia californica were examined in vivo and in vitro. Direct stimulation of R1 and L1 in the intact animal does not elicit any observable behavior, suggesting that they are neither motoneurons nor command neurons. These cells respond in vivo to sudden onset mechanical stimulation of widespread regions of the body. R1 and L1 spikes are initiated in at least three different loci: (1) the peripheral axon in the foot, (2) the neuropil of the pleural and/or pedal ganglion, and (3) the neuropil of the abdominal ganglion. Furthermore, R1 and L1 probably have two different mechanisms for spike initiation: (1) sensory (foot), and (2) synaptic (abominal and/or head ganglia). The different loci for spike initiation account for the bidirectional conduction of R1 and L1 spikes. As sensory (mechanoreceptor) neurons, R1 and L1 have peripheral axons in the ipsilateral posterior pedal nerve, show low threshold responses to stimulation of the ipsilateral posterior foot, they are rapidly adapting their responses do not decrease with repetion, and they are not blocked by high Mg++/low Ca++ solutions. As synaptically‐driven neurons, R1 and L1 have widespread bilateral responsiveness, their responses decrease with repetition and their inputs are blocked with high Mg++/low Ca++ solutions. These neurons integrate sensory and synaptic inputs and conduct bidirectionally, however, their output connections must be specified before their behavioral function can be understood.
Changes in synthesis of specific proteins following axotomy: Detection with two‐dimensional gel electrophoresis
Authors: Hall Michael E. , Wilson David L. , Stone George C. 
Published: January 2005

AbstractChanges in protein synthesis during development and following axotomy were analyzed by two‐dimensional gel electrophoresis. The two major postganglionic nerves emerging from the superior cervical sympathetic ganglia (SCSG) of adult rats were either cut or crushed unilaterally. At intervals ranging from 1 to 112 days after surgery both SCSG were removed and incubated for 1 hr in the presence of 14C‐leucine. Proteins were extracted and subjected to two‐dimensional electrophoretic separation and autoradiography. With this technique, proteins are separated on the basis of isoelectric point and molecular weight. Also, intact SCSG from 1, 2, 7, and 14 day old rats were labeled and analyzed.It was found that a minority of the separated proteins exhibited some detectable change in relative rate of synthesis following axotomy. Actin exhibited a slight (< 20%) increase in relative synthesis rate while tubulin did not change significantly. There were small but significant differences in the protein patterns following nerve crush, as opposed to nerve cut. Comparison of protein synthesis patterns from developing rat SCSG with those from intact and from axotomized adult SCSG failed to demonstrate any marked similarity between the developmental and the axotomy patterns.
Two mechanisms for spreading depression in the chicken retina
Authors: van Harreveld A. 
Published: January 2005

AbstractTwo mechanisms have been proposed to explain spreading depression (SD): one based on a release of glutamate (Van Harreveld, 1959), and the other on a release of potassium (Grafstein, 1956) from neuronal elements. Both glutamate and KCl cause transparency changes in the retina, comparable to those occurring in this tissue during SD. The glutamate effect is inhibited by MgCl2 (10 mM), in contrast to the transparency change due to KCl which is not affected by Mg++. Also SD is usually inhibited by MgCl2 which suggests that such SDs are based on a glutamate release. Impairment of the tissue metabolism promotes SDs which are insensitive to MgCl2. The resulting failure of the mechanisms that transport K+ and glutamate which leak out of the intracellular compartment back into the cells and fibers, seems to be involved in the generation of Mg++ insensitive SDs. This may facilitate either K‐based SDs or glutamate‐based SDs since the inhibitory effect of Mg++ is counteracted by an enhanced glutamate concentration. Both proposed mechanisms for SD seem to be possible under special circumstances.
Duplication of a spontaneously active neuron in Aplysia: Electrical coupling and effects of a phosphodiesterase inhibitor
Authors: Treistman Steven N. 
Published: January 2005

AbstractAn abdominal ganglion from an Aplysia californica is described, in which cell R15 has anomalously duplicated. The two cells exhibited a high degree of electrical coupling, assuring functional synchrony of output in the cells, which are characterized by a complex firing pattern. Exposure of this ganglion to the phosphodiesterase inhibitor IBMX caused a more altered firing rhythm in one of the cells, as well as an enhanced inhibitory component associated with the coupling potentials between cells, resulting in a loss of synchrony between the two cells.
The calcium‐dependent neuronal release of serotonin and its antagonism by lithium
Authors: Stefano George B. , Catapane Edward J. , Aiello Edward , Hiripi Laszlo 
Published: January 2005

AbstractThe cilio‐excitatory serotonergic innervation of lateral gill cilia of Mytilus edulis was studied in vivo. Peripheral serotonin release was dependent on the external calcium concentration. Serotonin release was inhibited by autodialyzing calcium from the tissue or by increasing the calcium concentration in the medium, as determined by measuring ciliary activity stroboscopically and by biochemical and radioassays of serotonin. Lithium also inhibited serotonin release when added to the external bathing medium. Concomitantly, altering calcium concentrations altered the degree of inhibition of serotonin release caused by lithium. The study demonstrates that the terminal release of the monoamine serotonin is a calcium‐dependent mechanism. The pharmacological effects of lithium in this system appear to be interrelated with the calcium‐dependent releasing mechanism.
The projections of neurosecretory cells in the brain of the North‐American medicinal leech, Macrobdella decora, using intracellular injection of horseradish peroxidase
Authors: Orchard I. , Webb Rodney A. 
Published: January 2005

AbstractThe projections of four anatomically distinct groups of putative neurosecretory cells found within the supra‐oesophageal ganglion of the leech Macrobdella decora were studied by intracellular injection of horseradish peroxidase. All four groups have their own characteristic branching pattern while sharing the common feature of possessing primary branches that project into the dorsal commissure. Numerous secondary processes extend from these primary branches to terminate within the neural lamella, as well as within the neuropile. Electron microscopy of the regions into which these secondary processes project reveals numerous neurosecretory terminals. The data suggests that the midregion of the dorsal commissure constitues a neurohemal complex. These observations strengthen the argument that the four groups of identified cells are indeed neurosecretory.
Neuronal mechanisms for bilateral coordination of salivary gland activity in Helisoma
Authors: Bahls Fred , Kater Stanley B. , Joyner Ronald W. 
Published: January 2005

AbstractThe salivary neuroeffector system of Helisoma consists of the paired salivary glands and buccal ganglia. Previous work demonstrated that neuronal control was required for coordination of activity in the two salivary glands. This neuronal control is provided by a pair of identified buccal ganglion neurons, 4R and 4L. This study examines the organization of this neuronal control and addresses the questions of monosynaptic vs. polysynaptic pathways as well as the bilateral effects of each neuron 4. Action potentials in neuron 4 elicit one‐for‐one EPSPs in a subpopulation of the salivary cells. These EPSPs can, in some cases, be increased by TEA injection into a neuron 4 and are unaffected by the addition of six‐times normal calcium. These data coupled with the constancy of synaptic transmission, as well as morphological evidence, further indicate the monosynaptic nature of the connection between neurons 4 and salivary secretory cells. Three different mechanisms exist to insure that activity in 4R and 4L result in coordinated activation of the salivary glands: (1) Lucifer Yellow injection and direct intracellular recording and stimulation demonstrate that both 4R and 4L can send axons to and innervate both salivary glands; (2) both 4R and 4L receive virtually identical synaptic input from higher‐order buccal ganglion neurons; and (3) 4R and 4L are electrically coupled. Thus, the system is organized with a high degree of redundancy, and bilateral synchrony of glandular activity is assured by mechanisms at various levels of neuronal organization.