bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for a dorso-medial parietal system involved in mental transformations of the body
Authors: Bonda E. , Frey S. , Petrides M.
Published: December 2017

1. The neural systems underlying body-space mental representation were studied by measuring changes in regional cerebral blood flow (CBF) with positron emission tomography in human subjects. 2. The experimental paradigm involved identification of the left or the right hand of the experimenter presented in different orientations or the palm of the subject's right hand. The subjects were required to decide whether it was the left or the right hand that was presented. To perform this task, the subjects had to move mentally the position of their own arm to adopt that of the experimenter's arm. The control condition involved the same type of tactual stimulation without the requirement of mental transformations of the subject's body position. The distribution of CBF was measured by means of the water bolus H2(15)O methodology during the performance of these tasks. 3. Comparison of the distribution of CBF between the experimental and control tasks was carried out to reveal changes specific to the mental transformations of the subject's body. Significant blood flow increases were observed in the caudal superior parietal cortex, including the intraparietal sulcus, and the adjacent medial parietal cortex. These findings demonstrated that there is a dorsomedially directed parietal system underlying mental transformations of the body in interactive relation with external space.
Neuronal synchronization of tonically active neurons in the striatum of normal and parkinsonian primates
Authors: Raz A. , Feingold A. , Zelanskaya V. , Vaadia E. , Bergman H.
Published: December 2017

1. Previous studies indicate that tonically active neurons (TANs) are the cholinergic interneurons of the striatum and predict that their activity is synchronized. To test whether TANs do fire synchronously, and whether dopamine depletion affects their synchronization, we recorded the simultaneous activity of several TANs in the putamens of two vervet monkeys before and after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment. 2. Cross-correlation analysis revealed that most pairs of TANS (33 of 54; 61.1%) fire synchronously at +/- 60-ms delay. Correlated activity was more common between neurons with characteristic response to reward (17 of 19 pairs; 89.5%). 3. Cross-correlation study of 24 triplets of TANS showed synchronization of spiking activity of all 3 TANS in only 29.2% of cases (7 of 24 triplets). Correlated activity of two of three possible pairs was found in 25% of the cases. 4. After MPTP treatment and the development of parkinsonian symptoms, most TANS' auto- and cross-correlograms (22 of 28 units; 78.6%; and 23 of 28 pairs; 82.1%) became oscillatory. The number of correlated pairs was slightly increased (24 of 28; 85.7%). The strength of the synchronization was not significantly different from the normal values. 5. These findings support the notion that TANs function as distributed, partially overlapping synchronized networks. However, a normal dopaminergic system is not essential for synchronization of TANs; on the contrary, dopaminergic activity may even have a desynchronizing effect on the basal ganglia's system.
A cardiac-like sodium current in motor neurons of a jellyfish
Authors: Grigoriev N. G. , Spafford J. D. , Przysiezniak J. , Spencer A. N.
Published: December 2017

1. Whole cell voltage-clamp recordings from isolated swimming motor neurons (SMNs) reveal a rapidly activating and inactivating sodium current. 2. Permeability ratios of PLi/PNa = 0.941 and P(guanidinium)/PNa = 0.124 were measured for the mediating channel, which was impermeable to rubidium. 3. The conductance/voltage and steady state inactivation curves are shifted in a depolarizing direction by approximately 45 mV relative to most neuronal sodium currents in higher animals. 4. Activation could be fitted with two exponents and maximal current peaked at 0.74 +/- 0.06 ms (mean +/- SD). 5. Inactivation could be fitted with fast (Tau 1 = 1.91 +/- 0.07 ms at +10 mV) and slow (Tau 2 = 11.65 +/- 0.55 ms at +10 mV) exponents. 6. Half-recovery from inactivation occurred slowly (52.6 +/- 2.9 ms). 7. A second class of identifiable neurons, "B" neurons, possesses a distinctly different population of sodium channels. they showed different inactivation kinetics and far more rapid recovery from inactivation (half-recovery < 5 ms). 8. We conclude that there was physiological diversification of sodium channels early in metazoan evolution and that there has been considerable cell-specific selection of channel properties.
Decreased duration of Ca(2+)-mediated plateau potentials in striatal neurons from aged rats
Authors: Dunia R. , Buckwalter G. , Defazio T. , Villar F. D. , McNeill T. H. , Walsh J. P.
Published: December 2017

1. The influence of age on striatal neuron Ca2+ physiology was studied through an analysis of intracellularly recorded Ca(2+)-mediated plateau potentials. In vitro brain slices from young and aged rats were treated with the K+ channel blocker tetraethylammonium (30 mM) to facilitate the expression of plateau potentials. A sample of neurons was also filled with biocytin and post hoc correlations were performed between morphology and physiology. 2. Testing of sampling parameters in neurons from young rats revealed that tetrodotoxin did not affect the amplitude or duration of plateau potentials. The membrane potential induced during plateau testing and the rate of plateau potential generation, however, had to be held constant because these variables affected plateau potential duration. 3. A significant age-related decrease was found in the duration of Ca(2+)-mediated plateau potentials that could not be explained by alterations in the activation or inactivation properties of the plateau potential. Investigation into relationships between cell morphology and plateau potential duration revealed a number of correlations. Soma size and dendritic length were correlated with plateau potential duration, independent of age (hierarchical regression), and an age-related decrease in dendritic length but not in soma size was found. Spine density and plateau potential duration were also correlated, but the significance depended on the variance associated with age. These data indicate that the extent of somadendritic membrane (including spines) affects plateau potential duration in striatal neurons and that dendrite and spine loss in aged animals may contribute to age-related decreases in plateau potential duration. 4. The response to replacement of Ca2+ with Ba2+ was age dependent, with Ba2+ causing a greater increase in the duration of plateau potentials in young neurons. These data rule out an increase in Ca(2+)-mediated inactivation of Ca2+ channels as a primary cause for the shortening of plateau potentials in aged neurons. Our morphological findings suggest that dendritic regression in aged neurons may have reduced the number of Ca2+ channels participating in plateau potential generation, but other mechanisms related to changes in the type of Ca2+ channel expressed and possible differences in their inactivation kinetics may also contribute to the age-related change in plateau potential duration.
Modulation of regenerative membrane properties by stimulation of metabotropic glutamate receptors in rat deep dorsal horn neurons
Authors: Morisset V. , Nagy F.
Published: December 2017

1. Intracellular recordings were obtained from 111 dorsal horn neurons in lamina V, in an in vitro transverse spinal cord slice preparation of the cervical region from young rats. 2. Of these neurons, 28% showed voltage-dependent plateau potentials, mainly underlain by a tetrodotoxin-resistant dihydropyridine-sensitive Ca2+ current. When depolarized, neurons with plateau properties produced accelerating firing frequency, afterdischarge, and bistability. They also exhibited windup of action potentials when stimulated by repetitive intracellular injections of current. 3. Glutamate being the main excitatory transmitter released by primary afferents, we also considered the effects of specific agonists of metabotropic glutamate receptors and showed that they modulate positively (induce or enhance) plateau properties in the deep dorsal horn neurons.
Metabotropic glutamate receptor dependent EPSP and EPSP-spike potentiation in area CA1 of the submerged rat hippocampal slice
Authors: Breakwell N. A. , Rowan M. J. , Anwyl R.
Published: December 2017

1. We reexamined the important areas of conflict in (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid [(1S,3R)-ACPD]-induced potentiation of the field excitatory postsynaptic potential (EPSP) and, for the first time, investigated the role of mGluRs in EPSP-spike (E-S) coupling. 2. (1S,3R)-ACPD (10 microM) bath applied for 20 min consistently induced a long-lasting potentiation of the dendritic EPSP in area CA1 of submerged rat hippocampal slices, which was considerably faster in onset than described previously. 3. This effect was not associated with any change in presynaptic fiber volley but was dependent on both an intact CA3 connection, because removal of area CA3 blocked (1S,3R)-ACPD-induced potentiation, and also on functional N-methyl-D-aspartate (NMDA) receptors, because (1S,3R)-ACPD-induced potentiation was blocked by inclusion of the NMDA receptor antagonist D(-)-2-amino-5-phosphonopentanoic acid (AP5; 50 microM). 4. (1S,3R)-ACPD induced a long-lasting potentiation of the population spike (PS) amplitude that was consistently larger than that of the EPSP measured in the cell body area. This EPSP-PS (E-S) potentiation was blocked by inclusion of the gamma-aminobuturic acid-A (GABAA) receptor antagonist, picrotoxin (50 microM). 5. E-S potentiation induced by high-frequency stimulation (HFS), which was of the same magnitude as that induced by (1S,3R)-ACPD, was blocked by the mGluR-selective antagonist (+)-alpha-methyl-4-carboxyphenylglycine (+MCPG; 250 microM). +MCPG also blocked HFS-induced long-term potentiation (LTP) of the EPSP measured in the cell body. 6. These results suggest that (1S,3R)-ACPD-induced potentiation is NMDA receptor dependent, contrary to some previous findings, and provide further evidence that both synaptic and E-S potentiation induced by (1S,3R)-ACPD share common mechanisms of expression with HFS-induced LTP. The data emphasize the important role of mGluRs in induction of EPSP LTP and E-S potentiation.
Neuropeptide Y2 receptors inhibit the frequency of spontaneous but not miniature EPSCs in CA3 pyramidal cells of rat hippocampus
Authors: McQuiston A. R. , Colmers W. F.
Published: December 2017

1. Neuropeptide Y (NPY) inhibits synaptic excitation in hippocampal area CA3. We studied its site of action with the use of whole cell patch-clamp recordings from CA3 pyramidal cells of rat hippocampal slices in vitro. 2. Spontaneous excitatory postsynaptic currents (sEPSCs) were isolated with picrotoxin, to block gamma-aminobutyric acid-A receptors, whereas miniature excitatory postsynaptic currents (mEPSCs) were isolated by additionally treating the slice with tetrodotoxin (TTX) and/or Cd2+, sEPSCs and mEPSCs were eliminated by the excitatory amino acid antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (10 microM) and DL-2-amino-5-phosphonovaleric acid (50 microM), and were thus solely attributable to glutamate release. 3. The interval and amplitude distributions of sEPSCS and (TTX-isolated) mEPSCS were analyzed. Either NPY or the rapidly reversible, Y2-receptor-selective agonist [6-aminohexanoic5-24] NPY, ([ahx5-24]NPY) sharply increased the inter-sEPSC intervals in 16 of 16 neurons tested. In 11 of these cells, these agonists also simultaneously shifted the sEPSC amplitude distribution to somewhat smaller amplitudes, whereas in the remaining 5 cells, no concurrent effect on amplitudes was observed. By contrast, in 15 separate neurons treated with 1 microM TTX, neither NPY nor [ahx5-24]NPY altered either mEPSC amplitude or interval distributions of the mEPSCs. 4. To directly compare the effects of Y2 receptor activation on sEPSC and mEPSC properties, we applied [ahx5-24]NPY to the same cell in the absence and presence of TTX (n = 7). sEPSC intervals were characteristically increased by the Y2 agonist in all cells; in six of seven cells the sEPSC distribution was also shifted to smaller amplitudes. TTX application reduced the mean amplitude of the synaptic events more than did [ahx5-24]NPY, while increasing their intervals. [ahx5-24]NPY had no effect in TTX. 5. NPY, acting on a Y2 receptor, inhibits impulse-dependent synaptic excitation of CA3 pyramidal cells of the rat hippocampus by an entirely presynaptic action.
Reliability of spike propagation in arborizations of dorsal root fibers studied by analysis of postsynaptic potentials mediated by electrotonic coupling in the frog spinal cord
Authors: Dityatev A. E. , Clamann H. P.
Published: December 2017

1. Postsynaptic potentials were recorded in lumbar motoneurons of the frog in response to electrical activation of dorsal roots. After chemical synaptic transmission was blocked by replacing Ca2+ with Mg2+ in the superfusion medium, it was confirmed that the remaining electrical excitatory postsynaptic potentials (EEPSPs) recorded in motoneurons consisted of potential changes-produced by electrical coupling between the motoneurons and the stimulated axons. The EEPSPs could then be used as an assay to study the reliability of spike propagation into presynaptic terminals. 2. EEPSPs typically consisted of three components. The first was a small positive deflection (prespike or presynaptic volley) that could also be recorded extracellularly. The second component was a spikelike fast positive component and the third was a slow positive component that followed the second but had a distinct maximum and a slow decay. The amplitude of the fast component did not correlate with that of either the prespike or the slow component. 3. 4-Aminopyridine (0.1 mM), which widens action potentials by blocking K+ channels, increased the amplitude and width of EEPSPs. Heptanol (1-4 mM), which is known to be a blocker of electrical coupling, could block EEPSPs. 4. The amplitudes of EEPSPs evoked by dorsal root stimulation were compared at different temperatures (7.5-19.5 degrees C). A slight decrease of the amplitude of the fast component with increasing temperature (Q10 = 0.8) was within limits predicted by resistance-capacitance filtering of the presynaptic spike at the different temperatures, suggesting that the temperature does not affect propagation of the spike in this synapse. 5. The amplitude of the fast component of EEPSPs evoked by single-pulse and paired-pulse stimulation did not fluctuate more than the baseline noise in 37 experiments in which the SD of baseline noise was < 100 microV. We conclude that electrical synaptic transmission does not fluctuate intermittently in this system, and that branch points conduct or fail to conduct for periods of time longer than the longest period in the analyzed experiments.
Inhibition of transmitter release shortens the duration of the excitatory synaptic current at a calyceal synapse
Authors: Otis T. S. , Trussell L. O.
Published: December 2017

1. We investigated the effect of reducing transmitter release on the time course of multiquantal, evoked synaptic currents to test for transmitter “cross talk” between neighboring synaptic release sites within a calyceal synapse. By using a brain slice preparation, neurons in the chick nucleus magnocellularis (nMAG) were voltage clamped and individual presynaptic axons were stimulated to evoke excitatory postsynaptic currents (EPSCs). 2. Application of 100-microM baclofen or 50-microM GABA in the presence of a gamma-aminobutyric acid-A (GABAA) receptor antagonist produced an 85% reduction of EPSCs, consistent with the activation of presynaptic gamma-aminobutyric acid-B (GABAB) receptors. In parallel with the reduction in the amplitude of the EPSC by GABAB receptor activation, the normally strong paired pulse depression (PPD) of the EPSC was converted to facilitation. The reduction in EPSC amplitude by gamma-aminobutyric acid (GABA) or baclofen was accompanied by a 20% reduction in the exponential time constant of decay of the EPSC. Weaker effects on the EPSC time course were observed for synapses with the least PPD. 3. Cd2+ (5 microM), which inhibits presynaptic calcium current, also reduced EPSC amplitude by 85% and converted PPD to facilitation. EPSCs were narrower in Cd2+, though less so than in baclofen. 4. The time course of the EPSC was longer than that of miniature synaptic currents, even after significant block by baclofen, GABA or Cd2+, indicating that dispersion of quantal release may help shape the synaptic waveform. However, the narrowing of the EPSC by baclofen, GABA, and Cd2+ suggests that high levels of quantal release at the calyceal synapse may delay the removal of transmitter, further slowing the EPSC.
Heterogeneity in Use-Dependent Depression of Inhibitory Postsynaptic Potentials in the Rat Neostriatum In Vitro
Authors: Radnikow Gabriele , Rohrbacher Jutta , Misgeld Ulrich
Published: December 2017

Radnikow, Gabriele, Jutta Rohrbacher, and Ulrich Misgeld. Heterogeneity in use-dependent depression of inhibitory postsynaptic potentials in the rat neostriatum in vitro. J. Neurophysiol. 77: 427–434, 1997. “Minimal stimulation” was applied to evoke responses in an “all-or-none” fashion in presumed medium spiny neurons of rat neostriatal slices in the presence of antagonists for glutamatergic excitation. For comparison, responses were evoked in the same cells by compound stimulation. Bicuculline (30 μM) blocked responses evoked by minimal stimulation, indicating that they were γ-aminobutyric acid-A (GABAA)-receptor-mediated inhibitory postsynaptic potentials (IPSPs), whereas responses evoked by compound stimulation were only reduced in amplitude. Likewise, R(−)baclofen (1–20 μM) blocked IPSPs evoked by minimal stimulation in all but one cell. On the contrary, responses evoked by compound stimulation were always reduced in amplitude but never blocked. Paired-pulse depression (PPD) of averaged responses to minimal and compound stimulation was observed at a stimulus interval of 300 ms. The GABAB receptor antagonist CGP55845A (0.5 μM) had no effect on PPD evoked by compound stimulation but abolished PPD evoked by minimal stimulation. In a second set of experiments, the two stimulation paradigms were used to evoke responses in neostriatal slices continuously bathed in R(−)baclofen (10–20 μM). In R(−)baclofen a strong PPD was evoked by minimal and by compound stimulation. The amplitude of the response to compound stimulation increased on application of CGP55845A (0.5 μM). At the same time, PPD evoked by compound stimulation decreased. On the contrary, IPSP amplitude and PPD evoked by minimal stimulation remained unchanged. We conclude that two types of GABAergic terminals exist in the rat neostriatum, only one of which is regulated by GABAB receptors. However, the other class of terminals, not regulated by GABAB receptors, displays a much more pronounced PPD.
Physiological and Theoretical Analysis of K+ Currents Controlling Discharge in Neonatal Rat Mesencephalic Trigeminal Neurons
Authors: Negro Christopher A. Del , Chandler Scott H.
Published: December 2017

Del Negro, Christopher A. and Scott H. Chandler. Physiological and theoretical analysis of K+ currents controlling discharge in neonatal rat mesencephalic trigeminal neurons. J. Neurophysiol. 77: 537–553, 1997. Whole cell voltage- and current-clamp recordings were obtained from mesencephalic trigeminal sensory (Mes 5) neurons identified visually in thin brain stem slices of neonatal rats with the use of infrared video microscopy. These cells exhibited accommodation in spike discharge responses to depolarizing current injection protocols whose duration differed as a function of holding potential (−50 vs. −65 mV). Several spikes were elicited before the membrane response accommodated from −50 mV, whereas from −65 mV only single action potentials were evoked. In response to similar protocols, application of the K+ channel blocker 4-aminopyridine (4-AP) (50 μM to 2 mM) caused sustained repetitive spiking whereas tetraethylammonium (TEA) (10–30 mM) did not cause repetitive spiking. In voltage clamp, 4-AP application (100 μM) revealed a sustained outward current ( I 4-AP) that was active between −60 and −30 mV. I 4-AP was responsible for suppressing sustained repetitive spiking behavior, producing accommodation under normal circumstances. TEA application in voltage clamp revealed a sustained outward current evoked positive to −40 mV. Two transient outward currents (TOCs) were identified by prepulse protocols typically used to characterizeA-type currents: a 4-AP-insensitive fast TOC, and a slow TOC( I TOC-S) sensitive to 4-AP (>500 μM). A Ca2+-dependent outward current that activated positive to −30 mV was also characterized. A mathematical model of a Mes 5 neuron was assembled from our voltage-clamp records to simulate the dynamic interaction of outward currents during membrane excitation. We conclude that in Mes 5 neurons, the 4-AP-sensitive currents I TOC-S and I 4-AP determine the duration of spike trains. In particular, the noninactivating I 4-AP determines whether cells exhibit sustained repetitive discharge or accommodate in response to depolarizing current. Neurotransmitter modulation of this current or modulation of the resting membrane potential could modify the output properties of Mes 5 neurons, and therefore the properties of these currents must be incorporated into our current understanding of how these cells contribute to shaping oral-motor pattern generation.
Time Course of Forward Masking Tuning Curves in Cat Primary Auditory Cortex
Authors: Brosch Michael , Schreiner Christoph E.
Published: December 2017

Brosch, Michael and Christoph E. Schreiner. Time course of forward masking tuning curves in cat primary auditory cortex. J. Neurophysiol. 77: 923–943, 1997. Nonsimultaneous two-tone interactions were studied in the primary auditory cortex of anesthetized cats. Poststimulatory effects of pure tone bursts (masker) on the evoked activity of a fixed tone burst (probe) were investigated. The temporal interval from masker onset to probe onset (stimulus onset asynchrony), masker frequency, and intensity were parametrically varied. For all of the 53 single units and 58 multiple-unit clusters, the neural activity of the probe signal was either inhibited, facilitated, and/or delayed by a limited set of masker stimuli. The stimulus range from which forward inhibition of the probe was induced typically was centered at and had approximately the size of the neuron's excitatory receptive field. This “masking tuning curve” was usually V shaped, i.e., the frequency range of inhibiting masker stimuli increased with the masker intensity. Forward inhibition was induced at the shortest stimulus onset asynchrony between masker and probe. With longer stimulus onset asynchronies, the frequency range of inhibiting maskers gradually became smaller. Recovery from forward inhibition occurred first at the lower- and higher-frequency borders of the masking tuning curve and lasted the longest for frequencies close to the neuron's characteristic frequency. The maximal duration of forward inhibition was measured as the longest period over which reduction of probe responses was observed. It was in the range of 53–430 ms, with an average of 143 ± 71 (SD) ms. Amount, duration and type of forward inhibition were weakly but significantly correlated with “static” neural receptive field properties like characteristic frequency, bandwidth, and latency. For the majority of neurons, the minimal inhibitory masker intensity increased when the stimulus onset asynchrony became longer. In most cases the highest masker intensities induced the longest forward inhibition. A significant number of neurons, however, exhibited longest periods of inhibition after maskers of intermediate intensity. The results show that the ability of cortical cells to respond with an excitatory activity depends on the temporal stimulus context. Neurons can follow higher repetition rates of stimulus sequences when successive stimuli differ in their spectral content. The differential sensitivity to temporal sound sequences within the receptive field of cortical cells as well as across different cells could contribute to the neural processing of temporally structured stimuli like speech and animal vocalizations.
Sensitivity of H-Reflexes and Stretch Reflexes to Presynaptic Inhibition in Humans
Authors: Morita H. , Petersen N. , Christensen L.O.D. , Sinkjær T. , Nielsen J.
Published: December 2017

Morita, H., N. Petersen, L.O.D. Christensen, T. Sinkjær, and J. Nielsen. Sensitivity of H-reflexes and stretch reflexes to presynaptic inhibition in humans. J. Neurophysiol. 80: 610–620, 1998. The sensitivity of soleus H-reflexes, T-reflexes, and short-latency stretch reflexes (M1) to presynaptic inhibition evoked by a weak tap applied to the biceps femoris tendon or stimulation of the common peroneal nerve (CPN) was compared in 17 healthy human subjects. The H-reflex was strongly depressed for a period lasting up to 300–400 ms (depression to 48 ± 23%, mean ± SD, of control at a conditioning test interval of 70 ms) by the biceps femoris tendon tap. In contrast, the short-latency soleus stretch reflex elicited by a quick passive dorsiflexion of the ankle joint was not depressed. The soleus T-reflex elicited by an Achilles tendon tap was only weakly depressed (92 ± 8%). The H-reflex was also significantly more depressed than the T-reflex at long intervals (>15 ms) after stimulation of CPN (H-reflex 63 ± 14%, T-reflex 91 ± 13%; P < 0.01). However, the short-latency (2 ms) disynaptic reciprocal Ia inhibition evoked by stimulation of CPN was equally strong for H- and T-reflexes (H-reflex 72 ± 10%, T-reflex 67 ± 13%; P = 0.07). Peaks in the poststimulus time histogram (PSTH) of the discharge probability of single soleus motor units ( n = 53) elicited by an Achilles tendon tap had a longer duration than peaks evoked by electrical stimulation of the tibial nerve (on average 5.0 ms as compared with 2.7 ms). All parts of the electrically evoked peaks were depressed by the conditioning biceps femoris tendon tap (average depression to 55 ± 27% of control; P < 0.001). A similar depression was observed for the initial 2 ms of the peaks evoked by the Achilles tendon tap (69 ± 48%; P < 0.001), but the last 2 ms were not depressed. Conditioning stimulation of the CPN at long intervals (>15 ms) also depressed all parts of the electrically evoked PSTH peaks ( n = 34; average 65%; P < 0.001) but had only a significant effect on the initial 2 ms of the peaks evoked by the Achilles tendon tap (85%; P < 0.001). We suggest that the different sensitivity of mechanically and electrically evoked reflexes to presynaptic inhibition is caused by a difference in the shape and composition of the excitatory postsynaptic potentials underlying the two reflexes. This difference may be explained by a different composition and/or temporal dispersion of the afferent volleys evoked by electrical and mechanical stimuli. We conclude that it is not straightforward to predict the modulation of stretch reflexes based on observations of H-reflex modulation.
Integration of Excitatory Postsynaptic Potentials in Dendrites of Motoneurons of Rat Spinal Cord Slice Cultures
Authors: Larkum Matthew E. , Launey Thomas , Dityatev Alexander , Lüscher Hans-R.
Published: December 2017

Larkum, Matthew E., Thomas Launey, Alexander Dityatev, and Hans-R. Lüscher. Integration of excitatory postsynaptic potentials in dendrites of motoneurons of rat spinal cord slice cultures. J. Neurophysiol. 80: 924–935, 1998. We examined the attenuation and integration of spontaneous excitatory postsynaptic potentials (sEPSPs) in the dendrites of presumed motoneurons (MNs) of organotypic rat spinal cord cultures. Simultaneous whole cell recordings in current-clamp mode were made from either the soma and a dendrite or from two dendrites. Direct comparison of the two voltage recordings revealed that the membrane potentials at the two recording sites followed each other very closely except for the fast-rising phases of the EPSPs. The dendritic recording represented a low-pass filtered version of the somatic recording and vice versa. A computer-assisted method was developed to fit the sEPSPs with a generalized α-function for measuring their amplitudes and rise times (10–90%). The mean EPSP peak attenuation between the two recording electrodes was determined by a maximum likelihood analysis that extracted populations of similar amplitude ratios from the fitted events at each electrode. For each pair of recordings, the amplitude attenuation ratio for EPSP traveling from dendrite to soma was larger than that traveling from soma to dendrite. The linear relation between mean ln attenuation and distance between recording electrodes was used to map 1/ e attenuations into units of distance (μm). For EPSPs with typical time course traveling from the somatic to the dendritic recording electrode, the mean 1/ e attenuation corresponded to 714 μm; for EPSPs traveling in the opposite direction, the mean 1/ e attenuation corresponded to 263 μm. As predicted from cable analysis, fast EPSPs attenuated more in both the somatofugal and somatopetal direction than did slow EPSPs. For EPSPs with rise times shorter than ∼2.0 ms, the attenuation factor increased steeply. Compartmental computer modeling of the experiments with biocytin-filled and reconstructed MNs that used passive membrane properties revealed amplitude attenuation ratios of the EPSP traveling in both the somatofugal and somatopetal direction that were comparable to those observed in real experiments. The modeling of a barrage of sEPSPs further confirmed that the somato-dendritic compartments of a MN are virtually isopotential except for the fast-rising phase of EPSPs. Large, transient differences in membrane potential are locally confined to the site of EPSP generation. Comparing the modeling results with the experiments suggests that the observed attenuation ratios are adequately explained by passive membrane properties alone.
Ionic Mechanisms of Action of Neurotensin in Acutely Dissociated Neurons From the Diagonal Band of Broca of the Rat
Authors: Jassar Balvinder S. , Harris Kim H. , Ostashewski Paula M. , Jhamandas Jack H.
Published: December 2017

Jassar, Balvinder S., Kim H. Harris, Paula M. Ostashewski, and Jack H. Jhamandas. Ionic mechanisms of action of neurotensin in acutely dissociated neurons from the diagonal band of Broca of the rat. J. Neurophysiol. 81: 234–246, 1999. Whole cell recordings were performed on acutely dissociated neurons from the horizontal limb of the diagonal band of Broca (hDBB) from rats to elucidate the ionic mechanisms of action of neurotensin. Neurotensin caused a decrease in whole cell voltage-activated outward currents and failed to elicit a response when Ca2+ influx was blocked by changing the external solution to the one containing 0 mM Ca2+ and 50 μM Cd2+, suggesting the involvement of Ca2+-dependent conductances. Charybdotoxin, a specific blocker of voltage-sensitive calcium-activated K+ channels ( I C), caused a decrease in outward currents comparable with that caused by blocking calcium influx and occluded the neurotensin-induced decrease in outward currents. Similarly, 50 μM tetraethylammonium ions also blocked the neurotensin response. Also neurotensin reduced whole cell barium currents ( I Ba) and calcium currents ( I Ca). Amiloride and ω-conotoxin GVIA, but not nimodipine, were able to eliminate the neurotensin-induced decrease in I Ba. Thus T- and N- but not L-type calcium channels are subject to modulation by neurotensin, and this may account for its effects on I C. The predicted changes in action potential as a result of the blockade of currents through calcium channels culminating into changes in I C were confirmed in the bridge current-clamp recordings. Specifically, neurotensin application led to depolarization of the resting membrane potential, broadening of spike and a decrease in afterhyperpolarization and accommodation. These alterations in action potential characteristics that resulted in increased firing rate and excitability of the hDBB neurons also were produced by application of charybdotoxin. Neurotensin effects on these properties were occluded  by  2 - [(1 – 7 - chloro - 4 - quinolinyl) - 5 - (2, 6 - di - methoxyphenyl) pyrazol-3-yl) carbonylamino] tricyclo (3.3.1.1.)decan-2-carboxylic acid, a nonpeptide high-affinity neurotensin receptor antagonist. Neurotensin blockade of I C, possibly through I Ca, is a potential physiological mechanism whereby this peptide may evoke alterations in the cortical arousal, sleep-wake cycle, and theta rhythm.
Distinct Populations of NMDA Receptors at Subcortical and Cortical Inputs to Principal Cells of the Lateral Amygdala
Authors: Weisskopf Marc G. , LeDoux Joseph E.
Published: December 2017

Distinct populations of NMDA receptors at subcortical and cortical inputs to principal cells of the lateral amygdala. Fear conditioning involves the transmission of sensory stimuli to the amygdala from the thalamus and cortex. These input synapses are prime candidates for sites of plasticity critical to the learning in fear conditioning. Because N-methyl-d-aspartate (NMDA)-dependent mechanisms have been implicated in fear learning, we investigated the contribution of NMDA receptors to synaptic transmission at putative cortical and thalamic inputs using visualized whole cell recording in amygdala brain slices. Whereas NMDA receptors are present at both of these pathways, differences were observed. First, the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-receptor-mediated component of the synaptic response, relative to the NMDA component, is smaller at thalamic than cortical input synapses. Second, thalamic NMDA responses are more sensitive to Mg2+. These findings suggest that there are distinct populations of NMDA receptors at cortical and thalamic inputs to the lateral amygdala. Differences such as these might underlie unique contributions of the two pathways to fear conditioning.
Physiological consequences of ectopicagoutigene expression: the yellow obese mouse syndrome
Authors: WOLFF GEORGE L. , ROBERTS DEAN W. , MOUNTJOY KATHLEEN G.
Published: December 2017

Wolff, George L., Dean W. Roberts, and Kathleen G. Mountjoy. Physiological consequences of ectopic agouti gene expression: the yellow obese mouse syndrome. Physiol. Genomics 1: 151–163, 1999.—This review summarizes primary and downstream phenotypic manifestations, with emphasis on altered responsiveness to environmental stimuli, of dominant yellow mutations at the mouse agouti locus. Obvious effects include hyperinsulinemia, obesity, stimulation of somatic growth and tumorigenesis, and coat color. Downstream influences of hyperinsulinemia and obesity on the individual's physiology determine important components of the obese yellow agouti mouse syndrome. Collectively, the phenotypic aberrations described support the concept that identical genomes are expressed in a spectrum of physiological phenotypes that reflect the complex interdependence of gene-regulated physiological pathways and processes in the organism throughout extended, but temporally ordered, periods of fetal and neonatal development and aging. This summary identifies important areas for additional research and provides integrated information required for a systematic approach to the development of interventions for common adult human health problems.
Where Are Neurophysiologists Going?
Authors: Ito Masao
Published: December 2017

After the many successes in unravelling how individual neurons function and communicate with each other, much still remains to be learned about neuronal systems.
The Patch-Clamp Technique: Recording Ionic Currents Through Single Pores in the Cell Membrane
Authors: Petersen OH , Petersen CCH
Published: December 2017

When an intracellular electrode records an electrical event in the cell membrane, we know that there are changes in the membrane's permeability to various ions. These changes are mediated by membrane entities known as pores or ion channels. The advance of the patch-clamp technique, which permits the study of changes in individual ion channels, in the simplest case conforms to a simple open-close two-state model.
Activity-Related Fluctuations in Extracellular Ion Concentrations in the Central Nervous System
Authors: Sykova E
Published: December 2017

The aim of this review is to describe methods for the direct measurement of ionic activity in neural tissues, to present a survey of the data on the activity-related extracellular ionic fluctuations in brain and spinal cord, and to outline their possible significance as modulators of neuronal and synaptic activity.
Dependence of Cardiac Contractility on Myofibrillar Calcium Sensitivity
Authors: Ruegg JC
Published: December 2017

In the heart, contractility may be varied over a wide range. It is determined mainly by the myoplasmic free calcium ion concentration. However, alteration of the responsiveness of the myofilaments to calcium may also be important in regulating cardiac contractility, in particular following changes in sarcomere length, or in hypoxia, or after interventions with certain novel cardiotonic drugs.
Coupling of Function, Metabolism, and Blood Flow in the Brain
Authors: Kuschinsky W
Published: December 2017

Functional activity, metabolism, and blood flow in the brain, although locally heterogeneous, are tightly coupled. Blood flow is adjusted to local activity in two ways: 1) short-term, dynamic coupling mediated by local vasoactive factors that ensure second-to-second regulation;and 2) long-term, static coupling apparently mediated by changes in capillary density. Recognizing these two mechanisms permits one to distinguish apparent from real uncoupling.
Haemoglobin Switching
Authors: Wood WG
Published: December 2017

Haemoglobin switching involves changes in production of the globin chains at specific times during vertebrate development. The hereditary haemolytic anaemias known as thalassaemias, which result from decreased or no synthesis of one of the globins, are some of the most common genetic diseases of humans.
New Concepts in Chronopharmacology
Authors: Reinberg A
Published: December 2017

Modern chronopharmacology investigates how drug effects vary with biological timing and endogenous periodicities. The goal is to improve the understanding of periodic and thus predictable changes in drug effects, and a specific aim is to solve problems of drug optimization. Knowledge of those administration times that coincide with the highest effectiveness and/or tolerance is required to optimize both timing and dosage of a medication.
Plasma Catechols - What Do They Mean?
Authors: Goldstein DS , Eisenhofer G
Published: December 2017

Tracer pharmacokinetic techniques are more accurate than antecubital venous plasma levels for measuring sympathoneural activity using plasma norepinephrine (NE). Combined measurements of NE and dihydroxyphenylglycol can be used to estimate the rate of neuronal reuptake of endogenous NE. Plasma dihydroxyphenylalanine, derived substantially from sympathic nerve endings and the brain, may reflect the rate of catecholamine synthesis.
Gap junction Heterogeneity in Liver, Heart, and Lens
Authors: FitzGerald PG
Published: December 2017

Gap junctions are nearly ubiquitous structures that ionically and metabolically couple adjacent cells. Molecular analysis of junctional proteins is establishing the presence of families of unique but homologous junctional proteins, opening the door to an explanation of tissue specificity in gap junction structure and function.
Molecular Basis of Lymphocyte-Mediated Destruction of Traget Cells
Authors: Young JD-E , Cohn ZA
Published: December 2017

Subsets of lymphocytes, known as cytotoxic T lymphocytes or natural killer cells, are potent killers of target cells. These immune cells have large granules in their cytoplasm containing cytotoxic peptides and other factors. Several of these molecules have been isolated and their functions elucidated.
Departments of Physiology in the Third World: The Struggle for Survival and Development
Authors: Sparks Harvey V. , Petropoulos Evangelos A.
Published: December 2017

Physiologists in Third World countries are working to establish teaching and research programs that can contribute to national development. To do this they need trained personnel, equipment, and the opportunity for sustained contact with physiologists in developed countries. By providing support attuned to local conditions, physiologists in wealthy nations can contribute to the solution of the special problems facing their fellow scientists in the developing world.
Mechanisms of Transcellular C1-Transport in Mammalian Renal Proximal Tubules
Authors: Sasaki S , Marumo F
Published: December 2017

In mammalian renal proximal tubule, a significant fraction of Cl- reabsorption passes through the cell by electroneutral mechanisms. At the apical membrane, Cl- is taken up into the cell by a Cl--base exchange, and it appears to exit the basolateral membrane through K+-Cl- cotransport and Na+-HCO3--Cl- exchange.
Membrane Remodelling During Reticulocyte Maturation
Authors: Johnstone RM , Teng K
Published: December 2017

During maturation, reticulocytes lose many membrane functions, including the transferrin receptor. Immunocytochemical studies reveal that after endocytosis the transferrin receptor (and many other membrane proteins) is packaged into multivesicular bodies. The vesicular contents are externalized by exocytosis. The specificity of such membrane processing underlies the changing properties of the cells' surfaces.
The Contributions of Willem Einthoven to Physiology
Authors: Snellen H. A.
Published: December 2017

Nobel Prize winner Willem Einthoven (1860-1927) used his genius for physical methods to develop electrocardiography and to explain the influence of the heart's position on the shape of the electrocardiogram.
Short-Term Autoregulation of Systemic Blood Flow and Cardiac Output
Authors: Cowley AWJ , Hinojosa-Laborde C , Barber BJ , Harder DR , Lombard JH , Greene AS
Published: December 2017

The contribution of local autoregulatory mechanisms to the overall control of the systemic circulation has been analyzed using theoretical and experimental approaches. Mechanisms that regulate regional vascular resistance and contribute importantly to the overall moment-to-moment regulation of cardiac output and total peripheral resistance are reviewed.
Experimental Models of Painful Peripheral Neuropathies
Authors: Bennett GJ
Published: December 2017

Several animal models are being used in the search for causes of painful conditions that occur when peripheral nerves are damaged by trauma or disease. Physiological, anatomical, and neurochemical abnormalities of possible pathogenetic significance have already been identified in both the peripheral and central nervous system.
Reflex Effects of Pulmonary Venous Congestion: Role of Vagal Afferents
Authors: Ravi K , Kappagoda CT
Published: December 2017

The rapidly adapting receptors of the lung are stimulated by changes in extravascular fluid space of the large airways. The natural stimulus to these receptors appears to be a fluid flux from the vasculature. These receptors are probably involved in certain reflexes associated with left ventricular dysfunction.
In Water Deprivation, Osmolality Becomes an Important Determinant of Aldosterone Secretion
Authors: Schneider EG
Published: December 2017

The adrenal gland secretion of aldosterone is closely linked to the volume and composition of the plasma compartment via the renin-angiotensin II system. In contrast, alterations in the plasma concentration of potassium and in plasma osmolality significantly alter aldosterone secretion by a direct action on the adrenal gland.
Sympathorenal Interactions in the Control of Cardiovascular Functions
Authors: Stella A , Golin R , Zanchetti A
Published: December 2017

Efferent renal nerve activity participates in the control of several renal functions: hemodynamics, renin release, and excretory functions. These renal functions are involved in cardiovascular homeostasis either by affecting peripheral resistances or volume balance. Also, afferent renal nerve activity can influence peripheral resistances and volume balance.
Teaching Physiology in Developing Countries: Report of a Meeting
Authors: Somjen George
Published: December 2017

The meeting was a satellite of the XXX1 IUPS Congress. Participants from 33 countries developed recommendations relating to the teaching of physiology in the Third World. Some concerns of our Third World colleagues will sound familiar to readers from the industrialized countries!
Ultrasonic Imaging of Musculoskeletal System
Authors: Shegal CM , Lewallen DG , Robb RA , Greenleaf JF
Published: December 2017

From tomographic images of ultrasonic attenuation and backscatter of animal bones, cross sections in any other plane can be computed by using advanced imaging software (ANALYZE). The resulting high-quality images very effectively discriminate between soft tissues and bones.
Afferent and Efferent Glomerular Arterioles: Their Role in Glomerular Filtrate Formation
Authors: Heller J
Published: December 2017

Glomerular capillaries, the site of glomerular filtration, are positioned between afferent and efferent arterioles. Interplay of these vessels plays an important role in determining filtration rate. Many hormones, autacoids, and drugs can differentially affect their tone, thereby modulating the glomerular filtration rate.
Alpha-Adrenergic Modulation of Cardiac Rhythm
Authors: Rosen MR , Anyukhovsky EP , Steinberg SF
Published: December 2017

Sympathetic cardiac innervation results in development of 41-kDa GTP regulatory protein that transduces the effect of alpha-1-agonist binding with Na-K pump stimulation and decreased automaticity. Activation of another alpha-1-receptor subtype increases automaticity, stimulates phosphatidylinositol metabolism, increases (Ca2+)i, and may induce arrhythmias during ischemia and reperfusion.
Modulation of the Oxygen-Carrying Function of Hemocyanin in Crustaceans
Authors: Truchot J-P , Lallier FH
Published: December 2017

The O2 affinity of crustacean hemocyanin is increased by several organic factors such as L-lactate and urate. These allosteric interactions, together with long-term changes of molecular subunit composition, allow fine tuning of the O2-carrying function to various environmental and physiological conditions.
Does Adenosine Function as a Retaliatory Metabolite in the Heart?
Authors: Belardinelli L , Shryock JC
Published: December 2017

Adenosine formation is augmented when the O2 supply is inadequate. Cardiac actions of adenosine can increase O2 supply (vasodilation) and decrease O2 consumption. We suggest that adenosine serves as a negative-feedback signal to correct an imbalance between O2 supply and consumption, thus acting as a cardioprotective metabolite.
Endothelium-Derived Relaxing Factor and Endothelin in Hypertension
Authors: Luscher TF , Dohi Y
Published: December 2017

In resistance arteries, endothelium-derived nitric oxide inhibits vasoconstrictors;this and endothelium-dependent relaxations to acetylcholine are blunted in hypertension. The sensitivity of hypertensive resistance arteries with endothelium to intraluminal endothelin-1 is normal but is reduced without endothelium. Thus hypertension impairs endothelial regulation of the resistance circulation.
Starling's "Law of the Heart": Rise and Fall of the Descending Limb
Authors: Elzinga Gijs
Published: December 2017

The descending limb of Starling's relationship between right atrial pressure and cardiac output was the cornerstone of his "law of the heart"; it was widely accepted in physiology. However, the original meaning of the law faded away over the years; the descending limb proved to be an experimental artefact.
Regulation by Nitroxidergic Nerve of Arterial Tone
Authors: Toda N , Okamura T
Published: December 2017

Nitric oxide plays a crucial role in transmitting information from nonadrenergic, noncholinergic vasodilator nerve to cerebroarterial smooth muscle. Since nitric oxide acts as transmitter, the nerve is termed "nitroxidergic." Mesenteric and temporal arterial tone appears to be regulated by reciprocal nitroxidergic and noradrenergic innervation.