bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential Effects of NGF and BDNF on Axotomy-Induced Changes in GABAA-Receptor-Mediated Conductance and Sodium Currents in Cutaneous Afferent Neurons
Authors: Oyelese Adetokunbo A. , Rizzo Marco A. , Waxman Stephen G. , Kocsis Jeffery D.
Published: December 2017

Oyelese, Adetokunbo A., Marco A. Rizzo, Stephen G. Waxman, and Jeffery D. Kocsis. Differential effects of NGF and BDNF on axotomy-induced changes in GABAA-receptor-mediated conductance and sodium currents in cutaneous afferent neurons. J. Neurophysiol. 78: 31–42, 1997. The effects of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) on injury-induced changes in the electrophysiological properties of adult rat cutaneous afferent dorsal root ganglion (DRG) neurons were examined. Whole cell patch-clamp techniques were used to study γ-aminobutyric acid-A (GABAA)-receptor-mediated conductance, voltage-dependent sodium currents, and action potential waveform in cutaneous afferent neurons (35–60 μm diam) cultured from control and axotomized animals. Cutaneous afferent neuronswere identified by retrograde labeling with hydroxy-stilbamidine (Fluoro-gold, a fluorescent retrograde axonal tracer); the sciatic nerve was transected 1 wk after Fluoro-gold injection and L4/L5 DRG neurons were cultured 2–3 wk after axotomy. NGF, BDNF, or Ringer (vehicle) solution was delivered in vivo directly to the transected sciatic nerve stump in axotomized rats via an osmotic pump. Recordings were obtained from neurons 5–24 h after culture. Axotomized neurons from rats treated with vehicle solution displayed a twofold increase in GABA-induced conductance and a prominent reduction in the proportion of neurons expressing action potentials that had inflections on the falling phase. The expression of kinetically slow tetrodotoxin (TTX)-resistant sodium current was markedly reduced and an increased expression of kinetically fast TTX-sensitive current was observed in neurons from vehicle-treated, axotomized rats. Treatment with NGF (0.25 μg/μl at 12 μl/day for 14 days) in axotomized animals resulted in an increase in the proportion of neurons expressing TTX-resistant, slow sodium currents and inflected action potentials, but had no effect on GABA-induced conductance. Treatment with BDNF (0.5 μg/μl at 12 μl/day for 14 days) attenuated the axotomy-induced increase in GABAA-receptor-mediated conductance while minimally affecting action potential waveform. The observed neurotrophin effects occurred independently of cell size changes. These findings indicate a differential regulation of GABAA receptor and sodium channel properties in axotomized rat cutaneous afferent neurons by specific neurotrophic factors.
Binocular Combination of Contrast Signals by Striate Cortical Neurons in the Monkey
Authors: Smith Earl L. , Chino Yuzo , Ni Jinren , Cheng Han
Published: December 2017

Smith, Earl L., III, Yuzo Chino, Jinren Ni, and Han Cheng. Binocular combination of contrast signals by striate cortical neurons in the monkey. J. Neurophysiol. 78: 366–382, 1997. With the use of microelectrode recording techniques, we investigated how the contrast signals from the two eyes are combined in individual cortical neurons in the striate cortex of anesthetized and paralyzed macaque monkeys. For a given neuron, the optimal spatial frequency, orientation, and direction of drift for sine wave grating stimuli were determined for each eye. The cell's disparity tuning characteristics were determined by measuring responses as a function of the relative interocular spatial phase of dichoptic stimuli that consisted of the optimal monocular gratings. Binocular contrast summation was then investigated by measuring contrast response functions for optimal dichoptic grating pairs that had left- to right-eye interocular contrast ratios that varied from 0.1 to 10. The goal was to determine the left- and right-eye contrast components required to produce a criterion threshold response. For all functional classes of cortical neurons and for both cooperative and antagonistic binocular interactions, there was a linear relationship between the left- and right-eye contrast components required to produce a threshold response. Thus, for example for cooperative binocular interactions, a reduction in contrast to one eye was counterbalanced by an equivalent increase in contrast to the other eye. These results showed that in simple cells and phase-specific complex cells, the contrast signals from the two eyes were linearly combined at the subunit level before nonlinear rectification. In non-phase-specific complex cells, the linear binocular convergence of contrast signals could have taken place either before or after the rectification process, but before spike generation. In addition, for simple cells, vector analysis of spatial summation showed that the inputs from the two eyes were also combined in a linear manner before nonlinear spike-generating mechanisms. Thus simple cells showed linear spatial summation not only within and between subregions in a given receptive field, but also between the left- and right-eye receptive fields. Overall, the results show that the effectiveness of a stimulus in producing a response reflects interocular differences in the relative balance of inputs to a given cell, however, the eye of origin of a light-evoked signal has no specific consequence.
Developmental Changes in the Hypoxic Response of the Hypoglossus Respiratory Motor Output In Vitro
Authors: Ramirez J. M. , Quellmalz U.J.A. , Wilken B.
Published: December 2017

Ramirez, J. M., U.J.A. Quellmalz, and B. Wilken. Developmental changes in the hypoxic response of the hypoglossus respiratory motor output in vitro. J. Neurophysiol. 78: 383–392, 1997. The transverse brain stem slice of mice containing the pre-Bötzinger complex (PBC), a region essential for respiratory rhythm generation in vitro, was used to study developmental changes of the response of the in vitro respiratory network to severe hypoxia (anoxia). This preparation generates, at different postnatal stages [postnatal day (P)0–22], spontaneous rhythmic activity in hypoglossal (XII) rootlets that are known to occur in synchrony with periodic bursts of neurons in the PBC. It is assumed that this rhythmic activity reflects respiratory rhythmic activity. At all examined stages anoxia led to a biphasic response: the frequency of rhythmic XII activity initially increased (“primary augmentation”) and then decreased (“secondary depression”). In neonates (P0–7), anoxia did not significantly affect the amplitude of integrated XII bursts. Secondary depression never led to a cessation of rhythmic activity. In mice older than P7, augmentation was accompanied by a significant increase in the amplitude of XII bursts. A significant decrease of the amplitude of XII bursts occurred during secondary depression. This depression led always to cessation of rhythmic activity in XII rootlets. The anoxia-induced response of the respiratory rhythmic XII motor output is biphasic and changes during development in a similar way to the in vivo respiratory network. Whether this biphasic response is due to a biphasic response of the respiratory rhythm generator and/or to a biphasic modulation of the XII motor nucleus remains unresolved and needs further cellular analysis. We propose that the transverse slice is a useful model system for examination of the mechanisms underlying the hypoxic response.
Nucleus Gracilis: An Integrator for Visceral and Somatic Information
Authors: Al-Chaer Elie D. , Westlund Karin N. , Willis William D.
Published: December 2017

Al-Chaer, Elie D., Karin N. Westlund, and William D. Willis. Nucleus gracilis: an integrator for visceral and somatic information. J. Neurophysiol. 78: 521–527, 1997. The nucleus gracilis (NG) receives an abundance of visceral input from various abdominal organs and is proposed to play an important role in visceral pain processing. The purpose of this study was to investigate the necessity of the NG for colorectal input into the ventral posterolateral (VPL) nucleus of the thalamus. Single-cell recordings were made from nine VPL cells isolated in nine different male Sprague Dawley rats anesthetized with pentobarbital sodium. Responses of the VPL cells to colorectal distension (CRD) and to cutaneous stimuli were obtained before and after lesioning of the NG. Electrolytic ( n = 5) and chemical ( n = 4) lesions of the NG were made in different preparations. The chemical lesions were made by injecting a solution of kainic acid into the NG. Kainic acid presumably kills neuronal cell bodies and spares axons of passage. The results indicate that a lesion of the NG, regardless of its type, reduces dramatically the responses of VPL neurons to innocuous cutaneous stimuli, and, to a lesser extent, the responses to CRD. Attenuation of VPL neuronal responses to CRD as well as to innocuous cutaneous stimuli by the NG lesions emphasizes the role of the dorsal column in visceral nociception and suggests that the NG is an integration center for visceral and cutaneous information flowing into the VPL nucleus.
Role of Group I Metabotropic Glutamate Receptors in the Patterning of Epileptiform Activities In Vitro
Authors: Merlin Lisa R. , Wong Robert K. S.
Published: December 2017

Merlin, Lisa R. and Robert K. S. Wong. Role of group I metabotropic glutamate receptors in the patterning of epileptiform activities in vitro. J. Neurophysiol. 78: 539–544, 1997. In guinea pig hippocampal slices, picrotoxin elicited spontaneous epileptiform bursts 300–550 ms in duration. Additional application of ( R,S)-3,5-dihydroxyphenylglycine or ( S)-3-hydroxyphenylglycine, agonists specific for group I metabotropic glutamate receptors(mGluRs), or (1 S,3 R)-1-aminocyclopentane-1,3-dicarboxylicacid, a broad-spectrum mGluR agonist, converted picrotoxin-induced interictal bursts into prolonged discharges measured on the order of seconds. The prolonged discharges induced by selective group I mGluR agonist continued to be produced for hours after agonist removal. The antagonists ( S)-4-carboxyphenylglycine and (+)-α-methyl-4-carboxyphenylglycine had no effect on the duration of picrotoxin-induced interictal bursts. However, after agonist exposure, the persistent prolonged discharges occurring in the absence of agonist were reversibly suppressed by the antagonists, suggesting that the activity is maintained via endogenous activation of group I mGluRs by synaptically released glutamate. Our results suggest that, under some conditions, activation of group I mGluRs produces long-lasting enhancement of synaptic responses, mediated at least in part by autopotentiation of the group I mGluR response itself, which may result in the production of seizure discharges and contribute to epileptogenesis.
Psychophysical Properties of the Trunk Midline
Authors: Spidalieri Giuseppe , Sgolastra Roberto
Published: December 2017

Spidalieri, Giuseppe and Roberto Sgolastra. Psychophysical properties of the trunk midline. J. Neurophysiol. 78: 545–549, 1997. This study was carry out to obtain direct evidence that the body midline actually is perceived and to assess some psychophysical properties of this line. Twelve normal, right-handed male subjects were asked to make accurate pointing movements toward the midline of the anterior trunk on the basis of their mental representation of this line. Each hand was used to point while the head was either aligned with the trunk or tilted 30° to the right or left. Analysis of end-positions of pointing on trunk images acquired by an image analysis system indicated that the trunk midline indeed is perceived as a straight line. Three putative trunk midlines were taken into consideration on the basis of anatomic landmarks, and it was found that the mental representation of the trunk midline came nearest to the line orthogonal to the intermammary line crossing its midpoint. The performing hand and the position of the head relative to the trunk both had an effect on the mental representation of the trunk midline. These findings suggest that somatosensory signals from the trunk, as well as proprioceptive input from the neck, contribute to the elaboration of the subject's mental representation of the trunk midline.
Spatiotemporal Receptive Field Organization in the Lateral Geniculate Nucleus of Cats and Kittens
Authors: Cai Daqing , Deangelis Gregory C. , Freeman Ralph D.
Published: December 2017

Cai, Daqing, Gregory C. DeAngelis, and Ralph D. Freeman. Spatiotemporal receptive field organization in the lateral geniculate nucleus of cats and kittens. J. Neurophysiol. 78: 1045–1061, 1997. We have studied the spatiotemporal receptive-field organization of 144 neurons recorded from the dorsal lateral geniculate nucleus (dLGN) of adult cats and kittens at 4 and 8 wk postnatal. Receptive-field profiles were obtained with the use of a reverse correlation technique, in which we compute the cross-correlation between the action potential train of a neuron and a randomized sequence of long bright and dark bar stimuli that are flashed throughout the receptive field. Spatiotemporal receptive-field profiles of LGN neurons generally exhibit a biphasic temporal response, as well as the classical center-surround spatial organization. For nonlagged cells, the first temporal phase of the response dominates, whereas for lagged neurons, the second temporal phase of the response is typically the largest. This temporal phase difference between lagged and nonlagged cells accounts for their divergent behavior in response to flashed stimuli. Most LGN cells exhibit some degree of space-time inseparability, which means that the receptive field cannot simply be viewed as the product of a spatial waveform and a temporal waveform. In these cases, the response of the surround is typically delayed relative to that of the center, and there is some blending of center and surround during the time course of the response. We demonstrate that a simple extension of the traditional difference-of-Gaussians (DOG) model, in which the surround response is delayed relative to that of the center, accounts nicely for these findings. With regard to development, our analysis shows that spatial and temporal aspects of receptive field structure mature with markedly different time courses. After 4 wk postnatal, there is little change in the spatial organization of LGN receptive fields, with the exception of a weak, but significant, trend for the surround to become smaller and stronger with age. In contrast, there are substantial changes in temporal receptive-field structure after 4 wk postnatal. From 4 to 8 wk postnatal, the shape of the temporal response profile changes, becoming more biphasic, but the latency and duration of the response remain unchanged. From 8 wk postnatal to adulthood, the shape of the temporal profile remains approximately constant, but there is a dramatic decline in both the latency and duration of the response. Comparison of our results with recent data from cortical (area 17) simple cells reveals that the temporal development of LGN cells accounts for a substantial portion of the temporal maturation of simple cells.
Reversal of LTP in the Hippocampal Afferent Fiber System to the Prefrontal Cortex In Vivo With Low-Frequency Patterns of Stimulation That Do Not Produce LTD
Authors: Burette F. , Jay T. M. , Laroche S.
Published: December 2017

Burette, F., T. M. Jay, and S. Laroche. Reversal of LTP in the hippocampal afferent fiber system to the prefrontal cortex in vivo with low-frequency patterns of stimulation that do not produce LTD. J. Neurophysiol. 78: 1155–1160, 1997. We examined the efficacy of several patterns of low-frequency stimulation for producing long-term depression (LTD) or depotentiation in the hippocampal fiber pathway to the prefrontal cortex in the anesthetized rat. Field potentials elicited by stimulation of the CA1/subicular region of the ventral hippocampus were recorded in the prelimbic area of the prefrontal cortex. We found no evidence that low-frequency trains (0.5–1 Hz), consisting of either single pulses, paired pulses (35-ms interpulse interval), or two-pulse bursts (5-ms interval), produce LTD in the prefrontal cortex. In contrast, all three stimulus protocols were found to induce a small-amplitude, persistent potentiation of the amplitude of the negative wave of the field response recorded in the prefrontal cortex. We also examined the ability of patterns of low-frequency stimulation to produce depotentiation of previously established long-term potentiation (LTP). Although low-frequency stimulation with single pulses or paired pulses was ineffective, we found that the two-pulse burst protocol selectively produced a rapid reversal of LTP in the hippocampo-prefrontal cortex pathway. Depotentiation is reversible and can be induced >2 h after the induction of LTP. Repeated trains failed to decrease the prefrontal cortex response below the original, unpotentiated level. These findings demonstrate the existence of a depotentiation mechanism that is capable of exerting powerful control over ongoing or recently induced synaptic plasticity in hippocampocortical connections in vivo.
Conditional Oculomotor Learning: Population Vectors in the Supplementary Eye Field
Authors: Chen Longtang L. , Wise Steven P.
Published: December 2017

Chen, Longtang L. and Steven P. Wise. Conditional oculomotor learning: population vectors in the supplementary eye field. J. Neurophysiol. 78: 1160–1163, 1997. We have shown previously that the activity levels and preferred directions of supplementary eye field neurons change as monkeys learn to associate nonspatial visual information with a saccade (or the spatial target of that saccade). The present report describes changes in neuronal population vectors (PV) during such learning. PVs based on neuronal activity shortly before and after saccades predicted movement direction poorly in the earliest stage of learning, but as monkeys mastered novel stimulus-response mappings, PV accuracy and magnitude increased significantly.
Evidence for Persistent Na+Current in Apical Dendrites of Rat Neocortical Neurons From Imaging of Na+-Sensitive Dye
Authors: Mittmann Thomas , Linton Shannon M. , Schwindt Peter , Crill Wayne
Published: December 2017

Mittmann, Thomas, Shannon M. Linton, Peter Schwindt, and Wayne Crill. Evidence for persistent Na+current in apical dendrites of rat neocortical neurons from imaging of Na+-sensitive dye. J. Neurophysiol. 78: 1188–1192, 1997. Evidence for a persistent Na+current ( INaP) in the apical dendrite of neocortical neurons was sought with the use of fluorescence imaging to measure changes in intradendritic Na+concentration. Neurons in neocortical brain slices were filled iontophoretically through an intracellular recording microelectrode with the Na+-sensitive dye benzofuran isophthalate (SBFI), and fluorescence images were recorded with a cooled charge-coupled device camera system using 380-nm illumination. In the presence of Ca2+and K+channel blockers, a short depolarizing current pulse evoked a single action potential followed by a plateau depolarization (PD) lasting >1 s. This tetrodotoxin (TTX)-sensitive PD is known to be maintained by INaP. A single action potential caused no detectable SBFI fluorescence change, whereas the PD was associated with an SBFI fluorescence change in the soma and apical dendrite indicating increased intracellular Na+concentration. Determination of the full spatial extent of the dendritic fluorescence change was prevented by our inability to detect the dim fluorescence signal in the distal regions of the apical dendrite. In each experiment the fluorescence change extended into the apical dendrite as far as dye could be visualized (50–300 μm). A slow, depolarizing voltage-clamp ramp that activated INaPcaused similar fluorescence changes that were eliminated by TTX, indicating that the SBFI fluorescence changes are caused by Na+influx due to INaPactivation. We conclude that INaPcan be generated by the apical dendritic membrane to at least 300 μm from the soma.
Membrane Properties and Monosynaptic Retinal Excitation of Neurons in the Turtle Accessory Optic System
Authors: Kogo Naoki , Ariel Michael
Published: December 2017

Kogo, Naoki and Michael Ariel. Membrane properties and monosynaptic retinal excitation of neurons in the turtle accessory optic system. J. Neurophysiol. 78: 614–627, 1997. Using an eye-attached isolated brain stem preparation of a turtle, Pseudemys scripta elegans, in conjunction with whole cell patch techniques, we recorded intracellular activity of accessory optic system neurons in the basal optic nucleus (BON). This technique offered long-lasting stable recordings of individual synaptic events. In the reduced preparation (most of the dorsal structures were removed), large spontaneous excitatory synaptic inputs [excitatory postsynaptic potentials (EPSPs)] were frequently recorded. Spontaneous inhibitory postsynaptic potentials were rarely observed except in few cases. Most EPSPs disappeared after injection of lidocaine into the retina. A few EPSPs of small size remained, suggesting that these EPSPs either were from intracranial sources or may have been miniature spontaneous synaptic potentials from retinal ganglion cell axon terminals. Population EPSPs were synchronously evoked by electrical stimulation of the contralateral optic nerve. Their constant onset latency and their ability to follow short-interval paired stimulation indicated that much of the population EPSP's response was monosynaptic. Visually evoked BON spikes and EPSP inputs to BON showed direction sensitivity when a moving pattern was projected onto the entire contralateral retina. With the use of smaller moving patterns, the receptive field of an individual BON cell was identified. A small spot of light, projected within the receptive field, guided the placement of a bipolar stimulation electrode to activate retinal ganglion cells that provided input to that BON cell. EPSPs evoked by this retinal microstimulation showed features of unitary EPSPs. Those EPSPs had distinct low current thresholds. Recruitment of other inputs was only evident when the stimulation level was increased substantially above threshold. The average size of evoked unitary EPSPs was 7.8 mV, confirming the large size of synaptic inputs of this system relative to nonsynaptic noise. EPSP shape was plotted (rise time vs. amplitude), with the use of either evoked unitary EPSPs or spontaneous EPSPs. Unlike samples of spontaneous EPSPs, data from many unitary EPSPs formed distinct clusters in these scatterplots, indicating that these EPSPs had a unique shape among the whole population of EPSPs. In most BON cells studied, hyperpolarization-activated channels caused a slow depolarization sag that reached a plateau within 0.5–1 s. This property suggests that BON cells may be more complicated than a simple site for convergence of direction-sensitive retinal ganglion cells to form a central retinal slip signal for control of oculomotor reflexes.
Local and Propagated Vascular Responses Evoked by Focal Synaptic Activity in Cerebellar Cortex
Authors: Iadecola Costantino , Yang Guang , Ebner Timothy J. , Chen Gang
Published: December 2017

Iadecola, Costantino, Guang Yang, Timothy J. Ebner, and Gang Chen. Local and propagated vascular responses evoked by focal synaptic activity in cerebellar cortex. J. Neurophysiol. 78: 651–659, 1997. We investigated the local and remote vascular changes evoked by activation of the cerebellar parallel fibers (PFs). The PFs were stimulated (25–150 μA, 30 Hz) in halothane-anesthetized rats equipped with a cranial window. The changes in arteriolar and venular diameter produced by PF stimulation were measured with the use of a videomicroscopy system. Cerebellar blood flow (BFcrb) was monitored by laser Doppler flowmetry and the field potentials evoked by PF stimulation were recorded with the use of microelectrodes. PF stimulation increased the diameter of local arterioles (+26 ± 1%, mean ± SE) in the activated folium ( n = 10, P < 0.05). The vasodilation was greatest in smaller arterioles (16.5 ± 0.8 μm), was graded with the intensity of stimulation, and was less marked than the vasodilation produced by hypercapnia in comparably sized vessels (+58 ± 5%, CO2 pressure = 50–60 mmHg, n = 8). In addition, the vasodilation was greatest along the horizontal beam of activated PFs and was reduced in arterioles located away from the stimulated site in a rostrocaudal direction. The increases in vascular diameter were associated with increases in BFcrb in the activated area (+55 ± 4%, n = 5). PF stimulation increased vascular diameter (+10 ± 0.5%, n = 10) also in larger arterioles (30–40 μm) located in the folium adjacent to that in which the PFs were stimulated. Higher-order branches of these arterioles supplied the activated area. No field potentials were evoked by PF stimulation in the area where these upstream vessels were located. The data suggest that increased synaptic activity in the PF system produces a “local” hemodynamic response mediated by synaptic release of vasoactive agents and a “remote” response that is propagated to upstream arterioles from vessels residing in the activated folium. These propagated vascular responses are important in the coordination of segmental vascular resistance that is required to increase flow effectively during functional brain hyperemia.
Arm Position Constraints During Pointing and Reaching in 3-D Space
Authors: Gielen C.C.A.M. , Vrijenhoek E. J. , Flash T. , Neggers S.F.W.
Published: December 2017

Gielen, C.C.A.M., E. J. Vrijenhoek, T. Flash, and S.F.W. Neggers. Arm position constraints during pointing and reaching in 3-D space. J. Neurophysiol. 78: 660–673, 1997. Arm movements in 3-D space were studied to investigate the reduction in the number of rotational degrees of freedom in the shoulder and elbow during pointing movements with the fully extended arm and during pointing movements to targets in various directions and at various distances relative to the shoulder, requiring flexion/extension in the elbow. The postures of both the upper arm and forearm can be described by rotation vectors, which represent these postures as a rotation from a reference position to the current position. The rotation vectors describing the posture of the upper arm and forearm were found to lie in a 2-D (curved) surface both for pointing with the fully extended arm and for pointing with elbow flexion. This result generalizes on previous results on the reduction of the number of degrees of freedom from three to two in the shoulder for the fully extended arm to a similar reduction in the number of degrees of freedom for the upper arm and forearm for normal arm movements involving also elbow flexion and extension. The orientation of the 2-D surface fitted to the rotation vectors describing the position of the upper arm and forearm was the same for pointing with the extended arm and for movements with flexion/extension of the elbow. The scatter in torsion of the rotation vectors describing the position of the upper arm and forearm relative to the 2-D surface was typically 3–4°, which is small considering the range of ∼180 and 360° for torsional rotations of the upper arm and the forearm, respectively. Donders' law states that arm posture for pointing to a target does not depend on previous positions of the arm. The results of our experiments demonstrate that the upper arm violates Donders' law. However, the variations in torsion of the upper arm are small, typically a few degrees. These deviations from Donders' law have been overlooked in previous studies, presumably because the variations are relatively small. These variations may explain the larger scatter of the rotation vectors for arm movements (3–4°) than reported for the eye (1°). Unlike for saccadic eye movements, joint rotations in the shoulder during aiming movements were not all single-axis rotations. On the contrary, the direction of the angular velocity vector varied during the movement in a consistent and reproducible way, depending on amplitude, direction, and starting position of the movement. These results reveal several differences between arm movements during pointing and saccadic eye movements. The implications for our understanding of the coordination of eye and arm movements and for the planning of 3-D arm movements are discussed.
Correlation of Peripheral Innervation Density and Dorsal Horn Map Scale
Authors: Wang Lei , Millecchia Ronald , Brown Paul B.
Published: December 2017

Wang, Lei, Ronald Millecchia, and Paul B. Brown. Correlation of peripheral innervation density and dorsal horn map scale. J. Neurophysiol. 78: 689–702, 1997. Dorsal horn map scale and peripheral innervation density were compared to test a hypothesized linear relationship. In anesthetized cats, low-threshold mechanoreceptive peripheral nerve innervation fields (IFs) were measured by outlining areas of skin from which action potentials could be elicited in cutaneous nerves. The same nerves were processed histologically and used to count myelinated axons. Innervation density for each nerve was calculated as number of axons divided by IF area. Single units were recorded throughout the hindlimb representation, in laminae III and IV. These data, combined with single-unit data from other animals and with cell counts in laminae III and IV, permitted estimation of numbers of cells whose receptive field centers fell in contiguous 1-cm bands from tips of toes to proximal thigh. A similar estimate was performed with the use of the nerve innervation data, so that peripheral innervation densities and map scales for the different 1-cm bands of skin could be compared. Correlation between the two was quite high ( r = 0.8), and highly significant ( P = 2.5 × 10−7). These results are consistent with a proposed developmental model in which map scale, peripheral innervation density, and reciprocal of dorsal horn cell receptive field size are mutually proportional, as a result of developmental mechanisms that produce constant divergence and convergence between primary afferent axons and dorsal horn cells.
Comparative Electrotonic Analysis of Three Classes of Rat Hippocampal Neurons
Authors: Carnevale Nicholas T. , Tsai Kenneth Y. , Claiborne Brenda J. , Brown Thomas H.
Published: December 2017

Carnevale, Nicholas T., Kenneth Y. Tsai, Brenda J. Claiborne, and Thomas H. Brown. Comparative electrotonic analysis of three classes of rat hippocampal neurons. J. Neurophysiol. 78: 703–720, 1997. We present a comparative analysis of electrotonus in the three classes of principal neurons in rat hippocampus: pyramidal cells of the CA1 and CA3c fields of the hippocampus proper, and granule cells of the dentate gyrus. This analysis used the electrotonic transform, which combines anatomic and biophysical data to map neuronal anatomy into electrotonic space, where physical distance between points is replaced by the logarithm of voltage attenuation (log A). The transforms were rendered as “neuromorphic figures” by redrawing the cell with branch lengths proportional to log A along each branch. We also used plots of log A versus anatomic distance from the soma; these reveal features that are otherwise less apparent and facilitate comparisons between dendritic fields of different cells. Transforms were always larger for voltage spreading toward the soma ( V in) than away from it ( V out). Most of the electrotonic length in V out transforms was along proximal large diameter branches where signal loss for somatofugal voltage spread is greatest. In V in transforms, more of the length was in thin distal branches, indicating a steep voltage gradient for signals propagating toward the soma. All transforms lengthened substantially with increasing frequency. CA1 neurons were electrotonically significantly larger than CA3c neurons. Their V out transforms displayed one primary apical dendrite, which bifurcated in some cases, whereas CA3c cell transforms exhibited multiple apical branches. In both cell classes, basilar dendrite V out transforms were small, indicating that somatic potentials reached their distal ends with little attenuation. However, for somatopetal voltage spread, attenuation along the basilar and apical dendrites was comparable, so the V in transforms of these dendritic fields were nearly equal in extent. Granule cells were physically and electrotonically most compact. Their V out transforms at 0 Hz were very small, indicating near isopotentiality at DC and low frequencies. These transforms resembled those of the basilar dendrites of CA1 and CA3c pyramidal cells. This raises the possibility of similar functional or computational roles for these dendritic fields. Interpreting the anatomic distribution of thorny excrescences on CA3 pyramidal neurons with this approach indicates that synaptic currents generated by some mossy fiber inputs may be recorded accurately by a somatic patch clamp, providing that strict criteria on their time course are satisfied. Similar accuracy may not be achievable in somatic recordings of Schaffer collateral synapses onto CA1 pyramidal cells in light of the anatomic and biophysical properties of these neurons and the spatial distribution of synapses.
Direct and Indirect Corticospinal Control of Arm and Hand Motoneurons in the Squirrel Monkey (Saimiri sciureus)
Authors: Maier M. A. , Olivier E. , Baker S. N. , Kirkwood P. A. , Morris T. , Lemon R. N.
Published: December 2017

Maier, M. A., E. Olivier, S. N. Baker, P. A. Kirkwood, T. Morris, and R. N. Lemon. Direct and indirect corticospinal control of arm and hand motoneurons in the squirrel monkey ( Saimiri sciureus). J. Neurophysiol. 78: 721–733, 1997. Anatomic evidence suggests that direct corticomotoneuronal (CM) projections to hand motoneurons in the New World squirrel monkey ( Saimiri sciureus) are weak or absent, but electrophysiological evidence is lacking. The nature of the corticospinal linkage to these motoneurons was therefore investigated first with the use of transcranial magnetic stimulation (TMS) of the motor cortex under ketamine sedation in five monkeys. TMS produced early responses in hand muscle electromyogram, but thresholds were high (compared with macaque monkey) and the onset latency was variable. Second, stimulation of the pyramidal tract (PT) was carried out with the use of chronically implanted electrodes in ketamine-sedated monkeys; this produced more robust responses that were markedly facilitated by repetitive stimulation, with little decrease in latency on the third compared with the first shock. Finally, postsynaptic potentials were recorded intracellularly from 93 arm and hand motoneurons in five monkeys under general chloralose anesthesia. After a single PT stimulus, the most common response was a small, slowly rising excitatory postsynaptic potential (EPSP), either alone (35 of 93 motoneurons) or followed by an inhibitory postsynaptic potential (39 of 93). The segmental delay of the early EPSPs was within the monosynaptic range (mean 0.85 ms); however, the rise time of these EPSPs was slow (mean 1.3 ms) and their amplitude was small (mean 0.74 mV). These values are significantly slower and smaller than EPSPs in a comparable sample of Old World macaque monkey motoneurons. The results show that CM connections do exist in the squirrel monkey but that they are weak and possibly located on the remote dendrites of the motoneurons. The findings are consistent with earlier anatomic studies. Repetitive PT stimulation produced large, late EPSPs in some motoneurons, suggesting that, in this species, there are relatively strong nonmonosynaptic pathways linking the corticospinal tract to hand motoneurons.
Electrophysiological Evidence for Two Transduction Pathways Within a Bitter-Sensitive Taste Receptor
Authors: Glendinning John I. , Hills Thomas T.
Published: December 2017

Glendinning, John I. and Thomas T. Hills. Electrophysiological evidence for two transduction pathways within a bitter-sensitive taste receptor. J. Neurophysiol. 78: 734–745, 1997. Among the sapid stimuli, those that elicit bitter taste are the most abundant and structurally diverse. To accommodate this diversity, animals are thought to use multiple bitter transduction pathways. We examined the role of individual taste receptor cells (TRCs) in this transduction process by focusing on one of the taste organs, or chemosensilla, of a caterpillar ( Manduca sexta). This chemosensillum (the lateral styloconicum) contains four functionally distinct TRCs: the salt, sugar, inositol, and deterrent TRCs, which are known to respond strongly to, in respective order, salts, sugars, inositol, and compounds humans describe as bitter. Using an extracellular recording technique, we tested three hypotheses for how a structurally diverse array of bitter compounds (salicin, caffeine, and aristolochic acid) could excite the same chemosensillum: several TRCs within the lateral styloconica respond to the bitter compounds; only the deterrent TRC responds to the bitter compounds, through a single transduction pathway; and only the deterrent TRC responds to the bitter compounds, but through multiple transduction pathways. To discriminate among these hypotheses, we tested five predictions. The first addressed how many TRCs within the lateral styloconica responded to the bitter compounds. Subsequent predictions were based on the results of the test of the first prediction and assumed that only the deterrent TRC responded to these compounds. These latter predictions addressed whether the bitter compounds acted through one or multiple transduction pathways. We obtained evidence consistent with the third hypothesis: only the deterrent TRC responded to the bitter compounds; the temporal patterns of firing and concentration-response curves elicited by caffeine and salicin were similar to each other, but different from those elicited by aristolochic acid; the patterns of sensory adaptation and disadaptation elicited by caffeine and salicin were similar to each another, but different from those elicited by aristolochic acid; reciprocal cross-adaptation occurred between caffeine and salicin, but not between aristolochic acid and caffeine or aristolochic acid and salicin; and the responsiveness of individual deterrent TRCs to caffeine and salicin correlated significantly, whereas that to aristolochic acid and caffeine or aristolochic acid and salicin did not. Taken together, these results indicate that the deterrent TRC contains at least two excitatory transduction pathways: one responds to caffeine and salicin and the other to aristolochic acid. To our knowledge, this is the first direct support for the existence of two bitter transduction pathways within a single TRC.
Involvement of cAMP-Dependent Protein Kinase in μ-Opioid Modulation of NMDA-Mediated Synaptic Currents
Authors: Xie Cui-Wei , Lewis Darrell V.
Published: December 2017

Xie, Cui-Wei and Darrell V. Lewis. Involvement of cAMP-dependent protein kinase in μ-opioid modulation of NMDA-mediated synaptic currents. J. Neurophysiol. 78: 759–766, 1997. We have previously reported dual effects of μ-opioids on N-methyl-d-aspartate (NMDA)-receptor-mediated synaptic events in the hippocampal dentate gyrus: an indirect facilitating effect via suppression of GABAergic interneurons (disinhibition) and a direct inhibitory effect in the presence of γ-aminobutyric acid-A (GABAA) antagonists. The cellular mechanism underlying the inhibitory effect of μ-opioids remains to be determined. In the present study we examine the role of adenosine 3′,5′-cyclic monophosphate (cAMP)-dependent protein kinase (PKA) in μ-opioid-induced inhibition of NMDA currents in rat hippocampal slices. NMDA-receptor-mediated excitatory postsynaptic currents (NMDA EPSCs) were evoked by stimulating the lateral perforant path and were recorded from dentate granule cells with the use of whole cell voltage-clamp techniques in the presence of the GABAA antagonist and a non-NMDA type of glutamate receptor antagonist. Two selective μ-agonists, [N-MePhe3, D-Pro4]-morphiceptin and [D-Ala2, N-MePhe4, Gly-ol5]-enkephalin, induced dose-dependent inhibition of NMDA EPSCs in a concentration range of 0.3–10 μM. This inhibitory effect could be completely reversed by the opioid antagonists naloxone or prevented by a selective μ-antagonist cyprodime, but was not affected by removal of Mg2+ from the external perfusion medium. Intracellular application of pertussis toxin (PTX) into the granule cell via whole cell recording pipettes completely prevented μ-opioid-induced reduction in NMDA currents, suggesting that a postsynaptic mechanism involving PTX-sensitive G proteins might be responsible for the inhibitory action of μ-opioids. Further studies were conducted to identify the intracellular messengers that coupled with G proteins and transduced the effect of μ-opioids in granule cells. The adenylate cyclase activator forskolin was found to enhance NMDA-receptor-mediated synaptic responses and to reverse the inhibitory effect of μ-opioids. Sp-cAMPS, a specific PKA activator, also enhanced NMDA EPSCs, whereas the PKA inhibitor Rp-cAMPS reduced NMDA EPSCs and occluded further inhibition of the current by μ-opioids. These findings strongly suggest that NMDA receptor function is subject to the modulation by PKA, and that μ-opioids can inhibit NMDA currents through suppression of the cAMP cascade in the postsynaptic neuron. Combined with our previous findings, the present results also indicate that μ-opioids can modulate NMDA-receptor-mediated synaptic activity in a complex manner. The net effect of μ-opioids in the dentate gyrus may depend on the interplay between its disinhibitory action, which facilitates NMDA-receptor-mediated responses, and its inhibitory action on the cAMP cascade.
Differential Activation of Glutamate Receptor Subtypes on a Single Class of Cells Enables a Neural Oscillator To Produce Distinct Behaviors
Authors: Spiro John E.
Published: December 2017

Spiro, John E. Differential activation of glutamate receptor subtypes on a single class of cells enables a neural oscillator to produce distinct behaviors. J. Neurophysiol. 78: 835–847, 1997. Electric fish generate different types of abrupt modulations of their electric organ discharge (EOD) rhythm to convey specific social signals. Intracellular recordings were made from neurons of the medullary pacemaker nucleus, which generates and transmits the rhythm that drives the EOD, to study the neuronal basis of two such modulations of the regular EOD rhythm, sudden accelerations, and abrupt interruptions. Recordings were both in vivo, and in a new in vitro brain preparation of Hypopomus pinnicaudatus (order Gymnotiformes). In vivo recordings during triggered behaviors indicated that abrupt modulations of the EOD rhythm are generated in the medullary pacemaker nucleus at the level of the relay cells, which are the projection cells of the nucleus, and not the pacemaker cells. In the in vitro brain stem preparation, cells of the pacemaker nucleus were spontaneously and rhythmically active as in the intact animal. Distinct modulations of the pacemaker nucleus rhythm that closely resembled those seen during natural behaviors could be triggered by electrical stimulation of afferent fibers. Modulations of the rhythm also could be triggered by direct pharmacological activation of the relay cells. When non- N-methyl-d-aspartate (NMDA) receptors were activated, relay cells were transiently depolarized and generated bursts of synchronized action potentials. NMDA receptor activation, alternatively, initiated a prolonged depolarization in the relay cells, during which time they failedto relay the regular pacemaker rhythm. The two firing states ofthe relay cell directly correlate with sudden accelerations and abrupt interruptions of the EOD.
Participation of Caudal Fastigial Nucleus in Smooth Pursuit Eye Movements. II. Effects of Muscimol Inactivation
Authors: Robinson Farrel R. , Straube Andreas , Fuchs Albert F.
Published: December 2017

Robinson, Farrel, R., Andreas Straube, and Albert F. Fuchs. Participation of the caudal fastigial nucleus in smooth pursuit eye movements. II. Effects of muscimol inactivation. J. Neurophysiol. 78: 848–859, 1997. We studied the effect of temporarily inactivating the caudal fastigial nucleus (CFN) in three rhesus macaques trained to make smooth pursuit eye movements. We injected the γ-aminobutyric acid A agonist muscimol into one or both CFNs where we had recorded pursuit-related neurons a few minutes earlier. Inactivating the CFN on one side impaired pursuit in one monkey so severely that it could not follow step-ramp targets moving at 20°/s, the target velocity that we used to test the other two monkeys. We tested this monkey with targets moving at 10°/s. In all three monkeys, unilateral CFN inactivation either increased the acceleration of ipsilateral step-ramp pursuit (in 2 monkeys, to 144 and 220% of normal) or decreased the acceleration of contralateral pursuit (in 1 monkey, to 71% of normal). Muscimol injected into both CFNs in two of the monkeys left both ipsilateral and contralateral acceleration nearly normal in both monkeys (101% of normal). Unilateral CFN inactivation also impaired the velocity of maintained pursuit as the monkeys tracked a target moving at a constant velocity or oscillating sinusoidally. Averaged across both types of movements in all three monkeys, gains for ipsilateral, contralateral, upward, and downward pursuit were 94, 67, 84, and 73% of normal, respectively. Unilateral CFN inactivation also impaired the monkeys' ability to suppress their vestibuloocular reflex (VOR). Averaged across the two monkeys VOR gain during suppression increased from 0.06 to 0.25 during yaw rotation and from 0.21 to 0.59 during pitch rotation. Bilateral CFN inactivation reduced pursuit gains in all directions more than unilateral injection did. In the two monkeys tested, ipsilateral, contralateral, upward, and downward gains went from 94, 86, 85, and 74% of normal, respectively, after we inactivated one CFN to 88, 73, 80, and 64% of normal after we also inactivated the second CFN. We can explain many, but not all, of the effects of CFN activation on smooth pursuit with the behavior of CFN neurons, and the assumption that the activity of each CFN neuron helps drive pursuit movements in the direction that best activates that neuron. We conclude that the CFN, like the flocculus-ventral paraflocculus, is a cerebellar region involved in control of smooth pursuit.