bluuebunny/crossref_metadata_2025 huggingface dataset:
Adaptive control for backward quadrupedal walking. I. Posture and hindlimb kinematics
Authors: Buford J. A. , Zernicke R. F. , Smith J. L.
Published: December 2017

1. To gain new perspectives on the neural control of different forms of quadruped locomotion, we studied adaptations in posture and hindlimb kinematics for backward (BWD) walking in normal cats. Data from four animals were obtained from high-speed (100 fr/s) cine film of BWD treadmill walking over a range of slow walking speeds (0.3-0.6 m/s) and forward (FWD) treadmill walking at 0.6 m/s. 2. Postural adaptations during BWD walking included flexion of the lumbar spine, compared to a relatively straight spine during FWD walking. The usual paw-contact sequence for FWD walking [right hindlimb (RH), right forelimb (RF), left hindlimb (LH), left forelimb (LF)] was typically reversed for BWD walking (RH, LF, LH, RF). The hindlimbs alternated consistently with a phase difference averaging 0.5 for both forms of walking, but the phasing of the forelimbs was variable during BWD walking. 3. As BWD walking speed increased from 0.3 to 0.6 m/s, average hindlimb cycle period decreased 21%, stance-phase duration decreased 29%, and stride length increased 38%. Compared to FWD walking at 0.6 m/s, stride length was 30% shorter, whereas cycle period and stance-phase duration were 17% shorter for BWD walking. For both directions, stance occupied 64 +/- 4% (mean +/- SD) of the step cycle. 4. During swing for both forms of walking, the hip, knee, and ankle joints had flexion (F) and extension (E1) phases; however, the F-E1 reversals occurred earlier at the hip and later at the knee for BWD than for FWD walking. At the ankle joint, the ranges of motion during the F and E1 phases were similar for both directions. During BWD walking, however, the knee flexed more and extended less, whereas the hip flexed less and extended more. Thus horizontal displacement of the limb resulted primarily from hip extension and knee flexion during BWD swing, but hip flexion and knee extension during FWD swing. 5. At the knee and ankle joints, there were yield (E2) and extension (E3) phases during stance for both forms of walking; however, yields at the knee and ankle joints were reduced during BWD walking. At the hip, angular motion was unidirectional, as the hip flexed during BWD stance but extended during FWD stance. Knee extension was the prime contributor to horizontal displacement of the body during BWD stance, but hip extension was the prime contributor to horizontal displacement during FWD stance. 6. Our kinematic data revealed two discriminators between BWD and FWD walking.(ABSTRACT TRUNCATED AT 400 WORDS)
APV-sensitive dorsal root afferent transmission to neonate rat sympathetic preganglionic neurons in vitro
Authors: Shen E. , Mo N. , Dun N. J.
Published: December 2017

1. Intracellular recordings were made from antidromically identified sympathetic preganglionic neurons (SPNs) in transverse thoracolumbar spinal cord slices from neonate (12- to 22-day-old) rats. 2. Electrical stimulation of dorsal roots or dorsal root entry zone elicited in SPNs an excitatory postsynaptic potential (EPSP) or multiple EPSPs of varying latencies. The EPSP could be graded by varying the stimulus intensity and, on reaching the threshold, discharged an action potential. 3. The dorsal root-evoked EPSPs had a mean synaptic latency of 2.6 ms (range: 1.2-11 ms), suggesting a polysynaptic pathway. The EPSPs were characteristically slow in onset with a mean rise time and half-decay time of 8.3 and 23 ms, respectively. 4. At the resting membrane potential of -50 to -60 mV, the amplitude of EPSPs recorded in normal (1.3 mM Mg2+) Krebs solution was reduced by membrane hyperpolarization or depolarization. In Mg2(+)-free solution, EPSPs were potentiated and reached threshold for spike discharge. 5. The EPSPs were suppressed by the nonselective glutamate receptor antagonist kynurenic acid (0.1-0.5 mM) and by the N-methyl-D-aspartate (NMDA) receptor antagonists D-2-amino-5-phosphonovaleric acid (APV; 1-10 microM) and ketamine (5-10 microM), but not by the quisqualate (QA)/kainate (KA) receptor antagonist 6,7-dinitroquinoxaline-2,3-dione (DNQX, 1-10 microM). The latter depressed the EPSPs elicited by stimulation of lateral funiculus in the same SPNs. 6. NMDA applied by pressure elicited a depolarization in the SPNs. In normal Krebs solution the response was voltage dependent with the peak amplitude occurring around -60 mV; conditioning depolarization or hyperpolarization diminished the response.(ABSTRACT TRUNCATED AT 250 WORDS)
Microstimulation mapping of precentral cortex during trained movements
Authors: Schmidt E. M. , McIntosh J. S.
Published: December 2017

1. The precentral cortex of three Macaca mulatta monkeys were mapped with intracortical microstimulation (ICMS) while the monkeys performed alternating wrist flexion and extension movements. A forearm cocontraction task was also employed with one monkey. Electromyogram (EMG) recordings from forearm muscles were used to evaluate the results of ICMS. 2. We have found that the results of ICMS can be misleading if EMG activity is not recorded from the responding muscle. Inhibition can be interpreted as excitation if muscle palpation or joint movement are the only response criteria. 3. Movement of the stimulating electrode by as little as 200 microns in a single radial column sometimes changed EMG responses from inhibition to excitation or vice versa, indicating that cortical inhibitory areas for a muscle can be located very close to excitatory zones. 4. Both excitation and inhibition of muscles could be produced with ICMS of precentral cortex when the animal was performing a task involving the muscles being mapped. EMG responses to ICMS were stable, provided that the stimulation was applied at the same time during a repetitive task such that the motoneurons were at a given level of excitability. 5. Zones where ICMS produced inhibition of a particular forearm muscle were interspersed among zones that produced excitation for that muscle. 6. Regions exist in precentral cortex where ICMS activates antagonistic wrist muscles producing cocontraction. 7. The extensive cortical region from which any individual muscle can be activated or suppressed with ICMS and the various combinations of muscles that are activated from within this region suggest that different types of movements involving a single muscle are represented at different locations within this region. 8. At a few locations in precentral cortex, the EMG responses to ICMS were not just a function of the level of excitation of the motoneuron pool at the time of stimulation but were also dependent on the specific task the monkey was performing at the time of stimulation.
Epileptiform activity induced by low chloride medium in the CA1 subfield of the hippocampal slice
Authors: Avoli M. , Drapeau C. , Perreault P. , Louvel J. , Pumain R.
Published: December 2017

1. Extracellular and intracellular recordings and measurements of the extracellular concentration of free K+ ([K+]o) were performed in the CA1 subfield of the rat hippocampal slice during perfusion with artificial cerebrospinal fluid (ACSF) in which NaCl had been replaced with equimolar Na-isethionate or Na-methylsulfate (hereafter called low Cl- ACSF). 2. CAl pyramidal cells perfused with low Cl- ACSF generated intracellular epileptiform potentials in response to orthodromic, single-shock stimuli delivered in stratum (S.) radiatum. Low-intensity stimuli evoked a short-lasting epileptiform burst (SB) of action potentials that lasted 40–150 ms and was followed by a prolonged hyperpolarization. When the stimulus strength was increased, a long-lasting epileptiform burst (LB) appeared; it had a duration of 4–15 s and consisted of an early discharge of action potentials similar to the SB, followed by a prolonged, large-amplitude depolarizing plateau. The refractory period of the LB was longer than 20 s. SB and LB were also seen after stimulation of the alveus. 3. Variations of the membrane potential with injection of steady. DC current modified the shape of SB and LB. When microelectrodes filled with the lidocaine derivative QX-314 were used, the amplitudes of both SB and LB increased in a linear fashion during changes of the baseline membrane potential in the hyperpolarizing direction. The membrane input resistance, as measured by injecting brief square pulses of hyperpolarizing current, decreased by 65-80% during the long-lasting depolarizing plateau of LB. 4. A synchronous field potential and a transient increase in [K+]o accompanied the epileptiform responses. The extracellular counterpart of the SB was a burst of three to six population spikes and a small increase in [K+]o (less than or equal to 2 mM from a resting value of approximately 2.5 mM). The LB was associated with a large-amplitude, biphasic, negative field potential and a large increase in [K+]o (up to 12.4 mM above the resting value). Changes in [K+]o during the LB were largest at the border between S. oriens and S. pyramidale. This was also the site where the field potentials measured 2–5 s after the stimulus attained their maximal amplitude. Conversely, field potentials associated with the early component of the LB or with the SB displayed a maximal amplitude in the S. radiatum. 5. Spontaneous SBs and LBs were at times recorded in the CA1 and in the CA3 subfield.(ABSTRACT TRUNCATED AT 400 WORDS)
Multiple site optical recording of transmembrane voltage (MSORTV), single-unit recordings, and evoked field potentials from the olfactory bulb of skate (Raja erinacea)
Authors: Cinelli A. R. , Salzberg B. M.
Published: December 2017

1. Multiple site optical recording of transmembrane voltage (MSORTV), together with conventional extracellular electrophysiological techniques were utilized with in vivo and in vitro preparations of the olfactory bulb of the Atlantic skate Raja erinacea to analyze electrical activity simultaneously in layers deep to the glomerular layer. 2. In the living animals and the in vitro isolated olfactory bulb, orthodromic stimulation evoked a compound action potential in the olfactory nerve fibers, followed by a series of early field-potential waves (N1, P1, N2, P2, N3, and N4). During paired stimulation experiments, unusual patterns of facilitation and suppression were observed for the N2 wave. 3. After orthodromic stimulation, single units, presumably mitral/tufted cells, exhibited a period of early discharge, followed by a period of suppression of spontaneous activity and of their test response in a pair stimulation paradigm. Some neurons also exhibited a labile period of reexcitation that was accompanied by a late surface negative field potential; these responses were also present in olfactory bulb slices. 4. Extrinsic absorption changes obtained from 500-microns saggital slices of the olfactory bulb, stained with the pyrazooxonal dye RH-155, consisted mainly of two types of depolarizing responses, a fast and a slow component, followed under some conditions by a late hyperpolarization. All signals exhibited wavelength dependences typical of the action spectrum of RH-155 and were abolished in the presence of tetrodotoxin (TTX) or high K+ in the bath. 5. The fast component of the optical signal represents synchronous compound action potentials conducted by the olfactory nerve fibers or evoked in the mitral/tufted somata and axonal pathways. The slow depolarizing optical signal appeared, after orthodromic stimuli, mainly in the zone between the glomeruli and the mitral/tufted layer; barium (1–10 mM), which depolarizes glial cells, increased its size and duration, suggesting that this signal does not reflect a glial response to [K+]o. 6. Different condition/test (C/T) intervals produced partial or complete suppression of the test response, depending on the recording site and the stimulus intensity. Just threshold orthodromic stimuli evoked an intermediate period of facilitation of the slow signals. A similar period was also observed in the N2 wave of the field potential. 7. Calcium channel blockers such as cadmium ion, or a low Ca2+ medium, suppressed the slow optical component whether evoked by orthodromic, antidromic, or direct stimulation. gamma-Aminobutyric acid (GABA) and baclofen also reduced or blocked the slow component of the extrinsic absorption signal.(ABSTRACT TRUNCATED AT 400 WORDS)
A calcium-dependent slow afterdepolarization recorded in rat dorsolateral septal nucleus neurons in vitro
Authors: Hasuo H. , Phelan K. D. , Twery M. J. , Gallagher J. P.
Published: December 2017

1. Conventional intracellular and single-electrode voltage-clamp recordings were obtained from rat brain slices containing dorsolateral septal nucleus (DLSN) neurons in vitro. 2. We observed a slow afterdepolarizing potential (slow-ADP) that lasted up to several seconds (half-decay time was in the range of 0.7-1.4 s) in almost 15% of DLSN neurons; these same neurons could exhibit burst firing activity. The amplitude of this slow-ADP was not affected by hyperpolarization of the membrane potential. 3. The slow-ADP was associated with an increased membrane conductance. Hybrid voltage clamping of the slow-ADP revealed a transient slow inward current (slow-ADC). The current-voltage relationship of the slow-ADC was linear between -40 and -100 mV and generated an extrapolated reversal potential of -30 mV. 4. We investigated the ionic mechanism of the slow-ADP in the rat DLSN. Slow-ADPs were not blocked by 1 microM tetrodotoxin (TTX) but were markedly depressed by 200 microM Cd2+, Ca2(+)-free, low-Na+ solutions, and the intracellular injection of ethylene glycol-bis(B-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA). Neither diltiazam (10 microM), an L-type Ca2+ channel blocker nor omega-conatoxin (0.2–2.5 microM), an N-type Ca2+ channel blocker affected the slow-ADP. Similarly, the slow-ADP was not affected in a low-Cl- solution. On the other hand, the slow-ADP was enhanced in a K(+)-free solution. In addition, the slow-ADP was not affected by 1 mM kynurenic acid, a broad-spectrum excitatory amino acid antagonist. 5. We conclude that the slow-ADP in the rat DLSN is mediated by a novel Ca2(+)-dependent, Na(+)-dependent, and nonsynaptic inward current that may be similar to the Ca2(+)-activated nonspecific cation channel currents (i.e., CAN-currents) described in various tissues. This current appears to underlie some forms of spontaneous bursting activity recorded from rat DLSN neurons. It may also be responsible for some types of bursting activity recorded in other CNS neurons
Initiation of epileptiform activity by excitatory amino acid receptors in the disinhibited rat neocortex
Authors: Lee W. L. , Hablitz J. J.
Published: December 2017

1. Intracellular recordings were obtained from neurons in layer II-III of rat frontal cortex maintained in vitro. The role of excitatory amino acid receptors in generation of picrotoxin (PTX)-induced epileptiform activity was investigated with the use of D-2-amino-5-phosphonovaleric acid (D-APV) and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) as selective antagonists of N-methyl-D-aspartate (NMDA) and non-NMDA receptors, respectively. 2. Bath application of PTX resulted in a decrease in evoked inhibitory postsynaptic potentials (IPSPs) in neocortical neurons and a concomitant increase in a polysynaptic late excitatory postsynaptic potential (IEPSP). Epileptiform burst responses, termed paroxysmal depolarizing shifts (PDSs), subsequently developed. Based on response duration, two types of PDSs were identified. Long PDSs were greater than 100 ms in duration, whereas short PDSs lasted less than 50 ms. An early depolarizing potential preceded both types of epileptiform burst response. 3. The NMDA receptor antagonist D-APV reduced the peak amplitude and duration of the PDS. D-APV-insensitive portions of the PDS were greatly attenuated or abolished by CNQX. The non-NMDA antagonist also increased the latency to PDS onset and reduced its duration without affecting peak amplitude. CNQX-insensitive components of the PDS, when present, were abolished by D-APV. 4. Short-duration PDSs could be blocked by CNQX. In these neurons, increasing the stimulation strength produced epileptiform responses of reduced amplitude. 5. Under control conditions, PDS amplitude was a linear function of membrane potential, increasing with hyperpolarization and diminishing on depolarization.(ABSTRACT TRUNCATED AT 250 WORDS)
Structure of the primate oculomotor burst generator. I. Medium-lead burst neurons with upward on-directions
Authors: Moschovakis A. K. , Scudder C. A. , Highstein S. M.
Published: December 2017

1. To investigate the structure of the primate burst generator for vertical saccades, we obtained intra-axonal records from vertical medium-lead burst neurons with upward on-directions (UMLBs) in alert, behaving squirrel monkeys, while monitoring their spontaneous eye movements. After physiological characterization, these UMLBs were injected with horseradish peroxidase. 2. UMLBs (n = 14) had no spontaneous activity and emitted bursts of action potentials that preceded rapid eye movements by approximately 6 ms. Parameters of the burst (duration and number of spikes) were highly correlated with parameters of the rapid eye movement (duration and amplitude of the upward displacement of the eyes). 3. The axons of six UMLBs projected to the oculomotor complex. Their somata (4 were recovered) were all in the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF). Their axons traveled caudally in the medial longitudinal fasciculus (MLF) and ramified in the interstitial nucleus of Cajal (NIC) before entering the oculomotor nucleus. Five axons terminated bilaterally in the subdivisions innervating the superior rectus and inferior oblique muscles and therefore were presumed to be excitatory. One axon terminated in the ipsilateral inferior rectus and superior oblique subdivisions of the oculomotor complex and was presumed to be inhibitory. 4. Additionally, our data demonstrate that the nucleus of the posterior commissure (nPC) may also contain UMLBs. The axon of one such neuron crossed the midline within the posterior commissure and provided terminal fields to the contralateral nPC, riMLF, NIC, and the mesencephalic reticular formation but not to the oculomotor complex. 5. In conclusion, our data demonstrate that the rostral mesencephalon of the monkey contains neurons that have both the activity and the connections that are necessary either to provide motoneurons innervating extraocular muscles of both eyes with the pulse of activity they display during upward saccades or to inhibit their antagonists. Furthermore, our data demonstrate that some UMLBs are better suited for closing the feedback path of the local feedback loop rather than for providing direct input to extraocular motoneurons.
Basal ganglia motor control. II. Late pallidal timing relative to movement onset and inconsistent pallidal coding of movement parameters
Authors: Mink J. W. , Thach W. T.
Published: December 2017

1. We have tested the hypothesis that the basal ganglia initiate some one or several modes of movement by recording the change in discharge frequency of pallidal neurons during visually triggered step and visually paced ramp moves in relation to the visual stimulus onset, the change in the electromyograph (EMG), and the movement onset of trained rhesus monkeys. 2. The modal times of change for globus pallidus pars interna (GPi) were significantly later than those for forearm agonist muscle EMG. By contrast, the modal time of change for the cerebellar dentate nucleus preceded that for wrist agonist EMG. 3. The direction of change in discharge frequency of the GPi cells was for 71% an increase and for 29% a decrease. 4. Because of the relatively late change of activity of GPi neurons, we propose that GPi neurons cannot initiate these movements, as others have also suggested. The commands for the initiation of these movements may instead be generated by structures that include the lateral cerebellum and the anterior cerebral cortex. 5. We have also tested the hypothesis that the pallidum of the basal ganglia or the dentate of the lateral cerebellum may control the direction and other parameters of the trajectory by recording from both structures to see whether cell discharge correlated with the parameter and whether the correlation was consistent across tasks. Two rhesus monkeys were trained to perform hold-ramp-hold and hold-step-hold visually guided movements in opposite directions by flexing and extending the wrist with and against uniform oppositely directed torque loads (0.2 Nm). Wrist position, velocity, force, and EMG were recorded simultaneously. Movement amplitudes and directional intent were computed and inferred, respectively. 6. Task related neurons were classified as follows: 1) directional, if the discharge rate was reciprocal for opposite movements or if it increased or decreased during movement in one direction only; 2) bidirectional, if the discharge rate increased or decreased during movement in both directions; and 3) "other," if it was directional under one load and bidirectional under the other. During step tracking, 34 GPi, 47 globus pallidus pars externa (GPe), and 44 cerebellar dentate nuclear neurons were related to the task. Of the GPi cells, 14 (41%) were directional, 6 (18%) bidirectional, and 14 (41%) other. Of the GPe neurons, 13 (28%) were directional, 19 (40%) bidirectional, and 15 (32%) other. Of the dentate cerebellar nuclear cells, 5 (11%) were bidirectional, 31 (70%) bidirectional, and 8 (18%) other.(ABSTRACT TRUNCATED AT 400 WORDS)
Axes of eye rotation and Listing's law during rotations of the head
Authors: Crawford J. D. , Vilis T.
Published: December 2017

1. The vestibuloocular reflex (VOR) was examined in four alert monkeys during rotations of the head about torsional, vertical, horizontal, and intermediate axes. Eye positions and axes were recorded in three dimensions (3-D). Visual targets were used to optimize gaze stabilization. 2. Axes of eye rotation during slow phases showed small but systematic deviations from collinearity with the axes of head rotation. These noncollinearities apparently resulted from vector summation of torsional, vertical, and horizontal VOR components with different gains. 3. VOR gain was lowest about a head-fixed torsional axis that was correlated with the primary gaze direction, as determined by Listing's law for saccades. As a result, rotation of the head about a partially torsional axis produced noncollinear slow phases, with axes that tilted toward Listing's plane. 4. During slow phases, eye position changed not only in the direction of rotation, but also systematically in other directions. Even axes of eye rotation within Listing's plane caused eye position to move out of the plane to a torsional position that was then held. Thus Listing's law for saccades cannot be a product of plant mechanics. 5. VOR slow phases were simulated with the use of a model that incorporated 3-D rotational kinematics into the indirect path and the oculomotor plant. This demonstrated that the observed pattern of position changes is the expected consequence of rotating the eye about a fixed axis and that to hold these positions the indirect path must employ a 3-D velocity-to-position transformation. 6. Quick phases not only corrected the violations of Listing's law produced by slow phases but anticipated them by directing the eye toward a plane rotated in the direction of head rotation. This was modeled by inputting the vestibular signal to a Listing's law operator that is shared by the quick phase and saccadic systems.
Regularity analysis in a compartmental model of chopper units in the anteroventral cochlear nucleus
Authors: Banks M. I. , Sachs M. B.
Published: December 2017

1. We investigate the discharge patterns of chopper units in the anteroventral cochlear nucleus (AVCN) by developing an equivalent cylinder compartmental model of AVCN stellate cells, which are the sources of the chopper response pattern. The model consists of a passive dendritic tree connected to somatic and axonal compartments with voltage-sensitive channels. Synaptic inputs to the model are simulated auditory nerve fiber responses to best-frequency tones. 2. We adjust the anatomic and electrical parameters of the model to agree with available intracellular data from stellate cells in the AVCN of the mouse and the cat and compare the response of the model to injected current with responses recorded in vitro. The model shows approximately linear current-voltage characteristics for small hyperpolarizing currents. The model's input resistance and the time course of its response to hyperpolarizing current applied at the soma are comparable with those measured from stellate cells in vitro. In response to sustained depolarizing current, the model fires repetitively with nearly perfect regularity, a property also observed in vitro. 3. Auditory nerve inputs to the cell are modeled as deadtime-modified Poisson processes with a multiexponential adaptation in the Poisson rate. We are able to adjust the number, rate, and location of excitatory and inhibitory inputs to the model and succeed in simulating chopper response patterns seen in vivo. 4. Chopper units exhibit a variety of regularity and adaptation patterns in response to tone stimuli. Physiological data from brain slice experiments and experiments in vivo imply that this heterogeneity is primarily due to differences in input configurations. By systematically varying the number and position of excitatory and inhibitory inputs, we can simulate a range of chopper response patterns. 5. We quantify the regularity of the model's response using the coefficient of variation (CV) of the interspike interval. We find that the CV decreases, i.e., the regularity increases, as the number of converging inputs or their distance from the soma increases. The regularity of the output is more sensitive to the number of converging inputs than to their location on the dendritic tree. The statistics of the first spike latency (FSL) are also sensitive to the configuration of excitatory inputs. The mean and minimum FSL are more sensitive to the electrotonic distance of the inputs from the soma than to the number of inputs, whereas the standard deviation of the FSL is highly dependent on the number of converging inputs and is nearly independent of their location.(ABSTRACT TRUNCATED AT 400 WORDS)
Control of motor-unit tension by rate modulation during sustained contractions in reinnervated cat muscle
Authors: Cope T. C. , Webb C. B. , Botterman B. R.
Published: December 2017

1. The aim of this study was to describe the control of tension by rate modulation of single motor units in reinnervated muscle. 2. Single fast-twitch motor units were isolated from medial gastrocnemius (MG) muscles in two groups of anesthetized adult cats: one in which the MG nerve was left untreated and another in which that nerve was sectioned and immediately sutured together 10-33 mo before study. Together with conventional measures of isometric contractile properties, units were tested with the use of computer-controlled feedback regulation of stimulation rate to maintain tension during continuous isometric contraction at a constant submaximal level [25% of maximal tension (Pmax)]. 3. For motor units from both groups, stimulation rate began to decline after target tension was attained and then settled at lower values for variable durations before rapidly increasing, usually within the last 5% of the contraction's duration, until reaching the experimentally selected limit of 100 pulses/s (pps). 4. Measures of the declining phase in stimulation rate occurring at the beginning of sustained contraction were not significantly different in comparison of untreated versus reinnervated muscles. These measures included 1) the magnitude of the decrease in rate, 2) the minimum rate attained, and 3) the time taken to reach minimum stimulation rate expressed as a fraction of endurance time (Et, total duration of the sustained contraction). 5. Most fast-twitch units from reinnervated muscles fell within normal limits for both endurance time and the number of stimuli applied over that period.(ABSTRACT TRUNCATED AT 250 WORDS)
Synaptic responses of guinea pig cingulate cortical neurons in vitro
Authors: Higashi H. , Tanaka E. , Nishi S.
Published: December 2017

1. Intracellular recordings were made from layer V/VI neurons of the guinea pig anterior cingulate cortex to investigate postsynaptic potentials (PSPs) evoked by electrical stimulation of the subcortical white matter (forceps minor). 2. Four distinct types of PSPs were recorded (at the resting potential) under normal physiological conditions; 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX)-sensitive excitatory postsynaptic potentials (EPSPs) were followed by bicuculline- or picrotoxin-sensitive depolarizing or hyperpolarizing inhibitory postsynaptic potentials (IPSPs), which were further followed by phaclofen-sensitive, long-lasting hyperpolarizing postsynaptic potentials (LPSPs). The average times-to-peak for the EPSP, depolarizing and hyperpolarizing IPSPs, and LPSP were 10, 22, 28, and 146 ms, respectively. 3. In the presence of CNQX and bicuculline, high-intensity electrical stimulation elicited a longer lasting EPSP with a time-to-peak of 21 ms. The amplitude and duration of the EPSP decreased with membrane hyperpolarization and increased with membrane depolarization. The EPSP was reversibly abolished by D,L-2-amino-5-phosphonovaleric acid (D,L-APV). 4. The bicuculline- or picrotoxin-sensitive depolarizing and hyperpolarizing IPSPs and the phaclofen-sensitive LPSP were markedly suppressed by CNQX, suggesting that glutamate (Glu) and/or aspartate nerve terminals project to GABAergic interneurons, and that the GABAergic interneurons are activated mainly by non-N-methyl-D-aspartate (non-NMDA) receptors. 5. In the presence of picrotoxin, the average reversal potential for the compound EPSP was 0 mV, which was similar to that (-6 mV) for the Glu-induced depolarization. In a solution containing D,L-APV at low concentrations, the average reversal potentials for the depolarizing and hyperpolarizing IPSPs and for the early and late components of the gamma-aminobutyric acid (GABA)-induced responses were -62, -72, -70, and -61 mV, respectively. Thus the value for the depolarizing IPSP was similar to that for the late response to GABA, whereas the value for the hyperpolarizing IPSP was almost the same as that for the early response to GABA. The average reversal potential of -90 mV for the LPSP was similar to -93 mV for the baclofen-induced hyperpolarization and to -94 mV for the spike afterhyperpolarization. 6. Application of phaclofen decreased the interspike interval of the spontaneous firing and reversed the increase in the interspike interval after subcortical stimulation. This result indicates that, even in a slice preparation, the anterior cingulate neurons are under tonic inhibitory control exerted by spontaneously active GABAergic interneurons.(ABSTRACT TRUNCATED AT 400 WORDS)
Disruption of binocularly correlated signals alters the postnatal development of spatial properties in cat striate cortical neurons
Authors: Chino Y. M. , Smith E. L. , Wada H. , Ridder W. H. , Langston A. L. , Lesher G. A.
Published: December 2017

1. Extracellular single-cell recording techniques were employed to investigate the effects of ocular misalignment on the postnatal development of the spatial response properties of striate cortical neurons. The primary objective of the study was to gain insight into the neural basis of strabismic amblyopia. 2. Two basic rearing strategies were used to study specific aspects of experimental strabismus in developing kittens. In one group, strabismus was optically induced by fitting kittens with goggles that held a 15-diopter base-in prism in front of one eye (MP) or both eyes (BP) between the ages of 4 wk and 4 mo. In the second group, a unilateral esotropia was surgically induced at 3 wks of age either by the simple resection of the lateral rectus muscle tendon (tenotomy) or by a more drastic procedure that involved removing sections of the lateral rectus and superior oblique muscles (myectomy). In addition, the eyelids of the nondeviating eyes of these kittens were sutured closed (ESO/MD). The first rearing paradigm isolated the effects of conflicting visual inputs on neural development, whereas the second procedure isolated the effects of anomalous ocular motility by producing a misalignment without putting the deviated eye at a competitive disadvantage. 3. The recording experiments were conducted when the animals were greater than or equal to 9 mo of age. A total of 445 striate cortical neurons were isolated and quantitatively studied in 17 cats (3 MPs, 3 BPs, 5 ESO/MDs, 3 goggle-reared controls, and 3 normals). In addition, we analyzed the distribution of preferred stimulus orientations of 1,205 single units that had been studied qualitatively in our previous investigation of 42 kittens reared with optically induced strabismus. 4. As expected, the proportion of binocularly driven units was reduced in both MP and BP cats. The great majority of units in ESO/MD animals were exclusively driven or highly dominated by the open deviating eye. 5. Prism-reared animals showed physiological deficits in spatial resolution, contrast sensitivity, contrast gain, and peak firing rate. These effects were manifest in both eyes, although there was always an interocular asymmetry in the deficits observed in the two eyes. In MP animals, the units dominated by the treated eye, which was contralateral to the recording hemisphere, were on the average more severely affected. The interocular asymmetry was smaller in BP cats; however, two of the three BP animals also showed a greater deficit in those units dominated by the contralateral eye.(ABSTRACT TRUNCATED AT 400 WORDS)
An intracellular study of muscle primary afferents during fictive locomotion in the cat
Authors: Gossard J. P. , Cabelguen J. M. , Rossignol S.
Published: December 2017

1. Presynaptic activity of identified primary afferents from flexor, extensor, and bifunctional hindlimb muscles was studied with intra-axonal recordings during fictive locomotion. Fictive locomotion appeared spontaneously in decorticate cats (n = 9), with stimulation of the mesencephalic locomotor region (n = 4), and in spinal cats injected with clonidine or nialamide and L-DOPA (n = 4). Representative flexor and extensor muscle nerves, recorded to monitor the locomotor pattern and dorsal rootlets of the sixth and seventh lumbar segments, were recorded simultaneously to monitor dorsal root potentials (DRPs). 2. From responses to muscle stretches and, in some instances, twitch contractions of the parent muscle, 75% of the single units examined were putatively identified as spindle afferents (40/53). On the basis of conduction velocity and stimulation threshold, 73% of these were further classified as group I fibers (29/40), the rest as group II fibers. 3. All units (n = 53 with resting potential more negative than -45 mV) showed fluctuations of their membrane potential (up to 1.5 mV) at the rhythm of the fictive locomotion. Subsequent averaging of these fluctuations over several cycles revealed that 89% of all units displayed a predominant wave of depolarization during the flexor phase, followed by a trough of repolarization. In 79% of the units, there was also a second, usually smaller, depolarization during the extensor phase. The relative size of each wave of depolarization could vary with different episodes of fictive locomotion in the same unit and among various afferents from the same muscle in the same experiment. 4. The firing frequency of some afferents from the ankle flexor tibialis anterior (5/16) and the bifunctional muscle posterior biceps-semitendinosus (4/15) was phasically modulated along the fictive step cycle. The maximum frequency always occurred during the flexor phase, i.e., during the largest depolarization of the unit. Because of the absence of phasic sensory input in the curarized animal, we assume that the phasic discharges were generated within the spinal cord and antidromically propagated. Phasic firing was never encountered in afferents from extensor muscles such as triceps surae (0/15) and vastus lateralis (0/4). 5. The results demonstrate that the pattern of rhythmic depolarization accompanying fictive locomotion is similar for the majority of flexor, extensor, and bifunctional group I (and possibly group II) muscle spindle primary afferents. They further indicate that there is a specific phasic modulation of antidromic firing for some flexor and bifunctional muscle spindle afferents.(ABSTRACT TRUNCATED AT 400 WORDS)
Electrophysiological evidence for a direct projection of direction-sensitive retinal ganglion cells to the turtle's accessory optic system
Authors: Rosenberg A. F. , Ariel M.
Published: December 2017

1. The direct retinal input pathway to the basal optic nucleus (BON), the primary nucleus of the turtle accessory optic system, was characterized physiologically. We tested the hypothesis that directional information encoded in retinal ganglion cells can influence the BON via a direct pathway. Using an in vitro whole-brain, eyes-attached preparation, we demonstrated the directness of this pathway by 1) antidromic activation of retinal ganglion cells from the contralateral BON and 2) orthodromic activation of the BON from the contralateral optic nerve. 2. Of 72 physiologically classified retinal ganglion cells, 9 could be antidromically activated from the contralateral BON with low current (less than 200 micro A). Eight of these cells were direction-sensitive (DS). The ninth cell did not respond to visual stimulus movement. The antidromic latencies ranged from 2.2 to 6.1 ms with a mean of 3.8 ms. These latencies were quite consistent for each cell, having an average SD of 0.08 ms. Moreover, consistent responses could always be recorded at stimulation rates up to 100 Hz. 3. With current stimulation of the contralateral optic nerve, the orthodromic conduction latency of 17 BON single units ranged from 2.5 to 6.6 ms with a mean of 4.6 ms. These latencies were more variable for an individual cell, having an average SD of 0.3 ms. Responses to individual current pulses could never be consistently evoked at stimulation rates greater than 40 Hz. 4. DS responses were recorded in BON single units after the removal of the dorsal midbrain, including the optic tectum and pretectum as well as the telencephalon. Three of these cells were activated orthodromically by current stimulation delivered to the contralateral optic nerve. Thus directional information reaches the BON via a direct projection from the contralateral retina. 5. Visual response properties of DS retinal ganglion cells were compared with those of BON cells to examine the transformations that take place in the brain stem. Applying a limacon model to the responses of both DS retinal ganglion cells and BON cells revealed that both types of cells have very similar direction tuning. However, the distribution of maximally responsive directions in the retina may differ from that of the BON. 6. Because DS retinal ganglion cells project directly to the BON, and because BON cells lose their direction sensitivity after retinal application of GABA antagonists, we conclude that the BON receives essential directional information directly from DS retinal ganglion cells. This directional information in the BON may represent a retinal slip error signal necessary for retinal image stabilization.
Osmotic effects on the CA1 neuronal population in hippocampal slices with special reference to glucose
Authors: Ballyk B. A. , Quackenbush S. J. , Andrew R. D.
Published: December 2017

1. Lowered osmolality promotes epileptiform activity both clinically and in the hippocampal slice preparation, but it is unclear how neurons are excited. We studied the effects of altered osmolality on the electrophysiological properties of CA1 pyramidal cells in hippocampal slices by the use of field and intracellular recordings. The excitability of these neurons under various osmotic conditions was gauged by population spike (PS) amplitude, single cell properties, and evoked synaptic input. 2. The orthodromic PS recorded in stratum pyramidale and the field excitatory postsynaptic potential (EPSP) in stratum radiatum were inversely proportional in amplitude to the artificial cerebrospinal fluid (ACSF) osmolality over a range of +/- 80 milliosmoles/kgH2O (mosM). The effect was osmotic because changes occurred within the time frame expected for cellular expansion or shrinkage and because permeable substances such as dimethyl sulfoxide or glycerol were without effect. Dilutional changes in ACSF constituents were experimentally ruled out as promoting excitability. 3. To test whether the field data resulted from a change in single-cell excitability, CA1 cells were intracellularly recorded during exposure to +/- 40 mosM ACSF over 15 min. There was no consistent effect upon CA1 resting potential, cell input resistance, or action potential threshold. 4. Osmotic alteration of orthodromic and antidromic field potentials might involve a change in axonal excitability. However, the evoked afferent volley recorded in CA1 stratum pyramidale or radiatum, which represents the compound action potential (CAP) generated in presynaptic axons, remained osmotically unresponsive with regard to amplitude, duration, or latency. This was also characteristic of CAPs evoked in isolated sciatic and vagus nerve preparations exposed to +/- 80 mosM. Therefore axonal excitability and associated extracellular current flow generated periaxonally are not significantly affected by osmotic shifts. 5. The osmotic effect on field potential amplitudes appeared to be independent of synaptic transmission because the inverse relationship with osmolality held for the antidromically evoked PS. Moreover, as recorded with respect to ground, the intracellular EPSP-inhibitory postsynaptic potential (IPSP) sequence (evoked from CA3 stratum radiatum) was not altered by osmolality. 6. The PS could occasionally be recorded intracellularly as a brief negativity interrupting the evoked EPSP. In hyposmotic ACSF, the amplitude increased and action potentials arose from the trough of the negativity as expected for a field effect. This is presumably the result of enhanced intracellular channeling of current caused by the increased extracellular resistance that accompanies cellular swelling.(ABSTRACT TRUNCATED AT 400 WORDS)
Effects of calcitonin gene-related peptide and efferent nerve stimulation on afferent transmission in the lateral line organ
Authors: Sewell W. F. , Starr P. A.
Published: December 2017

1. Calcitonin gene-related peptide (CGRP) is a 37-amino acid peptide immunolocalized in efferent fibers innervating hair-cell organs, including the lateral line organ of Xenopus laevis. CGRP, applied in nanomolar concentrations, increased the spontaneous discharge rate in afferent fibers innervating hair cells of the lateral line organ. 2. The increase in spontaneous discharge rate with application of CGRP was associated with an increase in the rate of occurrence of spontaneous excitatory postsynaptic potentials (EPSPs) and with little change in the amplitude of the EPSPs. 3. Prolonged (several hundred seconds) application of CGRP produced an increase in afferent fiber discharge rate that returned to control values in the continued presence of the peptide. 4. Efferent fibers were electrically stimulated to look for a non-cholinergic effect on spontaneous afferent discharge that might be attributed to CGRP. Electrical stimulation of the efferent fibers produced a rapid (100 ms) suppression of discharge rate followed by a rapid (100 ms) increase in discharge rate. However, both the rapid suppression and rapid excitation were likely to be mediated by the release of acetylcholine, because they were blocked by the application of the cholinergic blocking agents curare and atropine as well as by strychnine. 5. In almost one-half of the preparations examined, electrical stimulation of efferent fibers also produced a slowly developing increase in afferent discharge that could persist for several minutes after termination of the shocks. 6. This slow excitation by efferent stimulation was not blocked by concentrations of curare that blocked the rapid effects of efferent stimulation. Thus the slow effect is likely to be mediated by a receptor different from that for the rapid cholinergic effects. One possibility is that the excitation is mediated by the release of CGRP from the efferent nerve fibers.
The neuropeptide FMRFa both inhibits and enhances the Ca2+ current in dissociated Helix neurons via independent mechanisms
Authors: Yakel J. L.
Published: December 2017

1. The modulation of the voltage-activated Ca2+ current by the neuropeptide Phe-Met-Arg-Phe-NH2 (FMRFa) was investigated in dissociated central neurons from Helix aspersa using whole-cell voltage-clamp recording techniques. External Ba2+ was always used as the charge carrier in this study, and the intracellular Ca2+ concentration was buffered to 20 nM with ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA). 2. Run-down of the Ca2+ currents was not a problem as long as the neurons were dialyzed with a patch electrode filling solution containing ATP (1 or 2 mM). In ATP-dialyzed neurons, the rate of inactivation of the calcium current increased with time without any significant change in the rate of activation. However, when neurons were dialyzed with guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S; 100 microM; with ATP), the rate of inactivation decreased with time. There was no effect of GTP gamma S on the rate of activation of the Ca2+ current. This suggests that guanosine 5'-triphosphate (GTP)-binding proteins (G proteins) are able to modulate the rate of inactivation of the Ca2+ current in Helix neurons. 3. FMRFa both decreased and enhanced the amplitude of the Ca2+ current in these neurons. This inhibition was observed in most neurons, while the enhancement was observed in 20% of the neurons. Although the enhancement usually was preceded by the inhibitory response, sometimes the enhancement was observed separately. 4. The FMRFa-induced inhibition of the Ca2+ current usually consisted of a decrease in both the amplitude and the rate of inactivation of this current, effects that were reduced as the membrane potential was stepped to more depolarized potentials. A pertussis toxin (PTX)-sensitive G protein mediated this response, whereas no evidence was found to suggest the involvement of any known intracellular messenger. Therefore this inhibition may have resulted from a direct coupling between the FMRFa receptor and the Ca2+ channels via a PTX-sensitive G protein. 5. Arachidonic acid (100 microM) irreversibly reduced the amplitude of the Ca2+ current, but it did not alter the relative inhibition of this current by FMRFa. 6. The FMRFa-induced enhancement of the Ca2+ current was difficult to study because it was observed infrequently, and was rarely observed independently of the FMRFa-induced inhibitory response. In addition, the ability of FMRFa to enhance this current usually disappeared with time.(ABSTRACT TRUNCATED AT 400 WORDS)