bluuebunny/crossref_metadata_2025 huggingface dataset:
Climbing fiber responses of Purkinje cells to retinal image movement in cat cerebellar flocculus
Authors: Fushiki H. , Sato Y. , Miura A. , Kawasaki T.
Published: December 2017

1. The complex spike (CS) of the floccular Purkinje cell has been reported to be driven by retinal image movement in the rabbit, the rat, and the monkey, but not yet in the cat, in which the floccular neuronal network is well known. We recorded the CS activity together with concomitant simple spike (SS) activity of the floccular Purkinje cells that responded to large-field visual pattern movement in the anesthetized cat. 2. On the basis of the direction selectivity we divided the cells into two major types: the horizontal type that preferred horizontal stimuli and the vertical type that preferred vertical stimuli. The CS activity of the horizontal-type cell increased during stimuli directed contralaterally to the recording site and decreased during ipsilaterally directed stimuli, whereas that of the vertical-type cell increased during upward stimuli and decreased during downward stimuli. 3. In both types the CS response was larger at lower-velocity stimuli and the response was well maintained at higher-velocity stimuli < or = 180 degrees/s tested. The mean response decline was only 50% at stimulus velocities 90-150 degrees/s compared with the response amplitude at 2 degrees/s stimulus velocity. 4. The majority of the horizontal-type cells were modulated by the stimuli presented to either eye and the dominant eye was ipsilateral to the recording site. The majority of the vertical-type cells were also modulated by the stimuli presented to either eye without obvious differences between two eyes. 5. In both types the receptive field of the ipsilateral eye always included the area centralis and extended widely on both visual hemifields. The receptive field of the contralateral eye also included the area centralis and was usually restricted within the ipsilateral visual hemifield. The stimuli of small visual field (15 degrees x 15 degrees) projecting to the area centralis evoked especially large responses (70% of the full-screen response). 6. The CS and SS responses were reciprocal to each other, that is, when the CS firing increased the SS firing decreased and vice versa. 7. These CS responses are well suited for the direction detection of large-field retinal image motion at a wide velocity range. In light of the present unitary spike data together with the anatomic and eye movement data reported previously, we conclude that the cat flocculus is responsible for reduction of the large-field retinal image motion by producing eye movement in the same direction with the visual motion.
Dependence of LTP induction on postsynaptic depolarization: a perforated patch-clamp study in visual cortical slices of young rats
Authors: Yoshimura Y. , Tsumoto T.
Published: December 2017

1. To see whether there is a threshold of postsynaptic depolarization for induction of long-term potentiation (LTP) or depression (LTD) of synaptic transmission, perforated patch-clamp recordings were carried out under microscopic observation from 61 layer II/III neurons in visual cortical slices of young rats. Electrical stimulation given to nearby neurons was paired with stepwise shifts (30- or 300-ms duration) of clamped membrane potential of the recorded neurons to various levels. 2. Excitatory postsynaptic currents (EPSCs) were elicited by focal stimulation of a nearby pyramidal cell-like neuron. As the intensity of stimulation was increased, EPSCs emerged abruptly with 100% probability, and their peak latencies and amplitudes remained almost constant up to more than twice the threshold, indicating that the EPSCs were elicited monosynaptically. 3. LTP of EPSCs was induced in 11 of the 15 cells after pairing with a step to -20 mV and in 5 of the 14 cells after pairing with a step to -40 mV. No LTP was observed when the postsynaptic cells were clamped at -60, -70, or -90 mV. Significant LTD was not seen at any membrane potential level tested. There was no significant difference between the duration of potential shift of 30 and 300 ms during the pairing procedure in induction probability of LTP and magnitude of LTP, if it was induced. 4. These results suggest that LTP is induced by synaptic inputs associated with postsynaptic depolarization above the threshold around -40 mV at synapses linking layer II/III neurons in the developing visual cortex.
Characterization of the membrane ion currents of a model molluscan muscle, the accessory radula closer muscle of Aplysia californica. II. Depolarization-activated K currents
Authors: Brezina V. , Evans C. G. , Weiss K. R.
Published: December 2017

1. The accessory radula closer (ARC) muscle of Aplysia californica and its innervation is a model preparation for the study of the neural and cellular mechanisms of behavioral plasticity. Much of the plasticity is mediated by release of neurotransmitters and peptide cotransmitters that modulate contractions of the muscle. Preliminary to investigating the cellular mechanisms of action of these modulators, we have characterized the major membrane ion currents present in the unmodulated ARC muscle and their likely roles in normal contraction. We have studied single dissociated but functionally intact ARC muscle fibers under voltage clamp. This is the second of three papers describing this work. In the preceding paper we described the electrophysiological properties of the fibers at hyperpolarized voltages, and characterized the two major hyperpolarized-activated currents present, a classical inwardly rectifying K current and a Cl current induced by elevated intracellular Cl-. 2. In this paper we dissect the large outward current that becomes activated when the fibers are depolarized above -50 or -40 mV. We find that this current consists of two major depolarization-activated K currents, a fast transient “A”-type current and a slower maintained delayed rectifier, with perhaps a small component of Ca(2+)-activated K current. 3. The A current begins to activate with voltage steps above -50 or -40 mV. It activates in milliseconds, then inactivates virtually completely within 100–200 ms. It is fully available for activation below -80 mV, and almost completely inactivated above -40 mV. It is Ca2+ independent, half-maximally blocked by approximately 3 mM 4-aminopyridine (4-AP) but only 460 mM tetraethylammonium (TEA). 4. The delayed rectifier both activates and inactivates more slowly and more positive than the A current. Thus it begins to activate only above -30 or -20 mV; it activates in tens of milliseconds, then inactivates incompletely over several seconds; it is fully available below -70 mV and inactivated above 0 mV. It is Ca2+ independent, half-maximally blocked by 10 mM TEA and 3–10 mM 4-AP. 5. In the following paper we describe a depolarization-activated Ca current that underlies the K currents and most likely provides Ca2+ necessary for contraction of the muscle. By activating simultaneously with the Ca current, the K currents serve to prevent spikes, so that the depolarization is confined to a range where small voltage changes provide fine control over a wide range of contraction strengths.
A role for potassium currents in the generation of the swimming motor pattern of Xenopus embryos
Authors: Wall M. J. , Dale N.
Published: December 2017

1. To assess the role that K+ currents play in the production of the swimming motor pattern in the Xenopus embryo, we have used low doses of the K+ channel blockers, 3,4-diaminopyridine (3,4-DAP; 25–100 microM) and tetraethylammonium (TEA; 500 microM), to reduce K+ currents and investigated the effects on motor output. 2. To confirm that 3,4 -DAP and TEA block K+ currents and characterize their actions, we made whole -cell voltage -clamp recordings from acutely isolated spinal neurons. Both 25–100 microM 3,4 -DAP and 100–500 microM TEA blocked the sustained K+ current in a dose -dependent manner. 3. Because TEA can block acetylcholine nicotinic receptors on autonomic ganglia, and nicotinic acetylcholine receptors have recently been shown to be present on Xenopus spinal neurons, we have tested both 3,4 -DAP and TEA for antagonist action against the nicotinic agonist 1,1-dimethyl-4-phenylpiperazinium (DMPP). Although 500 microM TEA blocked the DMPP -induced depolarization, 25 microM 3,4-DAP did not. 4. In the intact embryo, application of 25–100 microM 3,4 -DAP or 500 microM TEA disrupted both the left and right alternation of ventral root discharge and the motor pattern recorded intracellularly from spinal neurons during swimming. Both blockers allowed the firing of an extra action potential at midcycle, which led to a number of different patterns. These patterns were categorized as follows: type A, cycles with midcycle action potentials; type B, the simultaneous firing of neurons on both sides of the cord; and type C, in which one side was active, whereas the other side was inhibited. In both 3,4-DAP and TEA these abnormalities tended to occur at the beginning of swimming episodes. Both blockers also caused a significant increase in the cycle period. Because both 3,4-DAP and TEA produced very similar affects to the motor pattern, we conclude that the perturbations are probably a result of reducing K+ current amplitude. 5. To investigate whether 3,4-DAP and TEA were producing disruptions in the motor pattern by increasing synaptic drive through the broadening of action potentials, we made measurements of spike width, tonic depolarization, and midcycle inhibitory postsynaptic potential (IPSP) amplitude during swimming. Both 3,4-DAP and TEA caused significant but modest spike broadening (20.8 and 29.8%, respectively); however, their effects on tonic depolarization were inconsistent although both blockers increased midcycle IPSP amplitude. 6. To test whether a reduction in K+ currents could plausibly produce the specific motor pattern perturbations that were seen, we have made computer simulations of simplified spinal networks.(ABSTRACT TRUNCATED AT 400 WORDS)
Effects of aging on the primate visual system: spatial and temporal processing by lateral geniculate neurons in young adult and old rhesus monkeys
Authors: Spear P. D. , Moore R. J. , Kim C. B. , Xue J. T. , Tumosa N.
Published: December 2017

1. Visual abilities decline during normal aging, and many of these declines are due to neural changes in the retina or central visual pathways. We have begun studies of the primate visual system to investigate the location and nature of these changes as well as to answer general questions about the effects of aging on neural function. We began with the dorsal lateral geniculate nucleus (LGN) because it is the main structure through which visual information passes on the way to cortex and because the parallel parvocellular and magnocellular pathways, which may be affected differently by aging, are anatomically distinct there. 2. Single -cell recordings were made in the LGN of young adult (5–16 yr) and old (25–28 yr) rhesus monkeys. We made quantitative measures of a wide variety of response properties for a large number of parvocellular (n = 257) and magnocellular (n = 113) neurons in the two groups of animals. As a result, in addition to studying the effects of aging, we were able to make quantitative comparisons between parvocellular and magnocellular neurons using larger samples than have been studied previously and for some properties that have not been studied before. 3. We found that magnocellular neurons have significantly higher maximal response rates and signal -to -noise ratios than parvocellular neurons. However, response latencies to visual stimulation were similar for neurons in the two types of layers. In agreement with previous studies, magnocellular neurons had higher maximal contrast sensitivity and higher contrast gain than parvocellular neurons. However, the sensitivity difference occurred because nearly all of the neurons with low sensitivities (< 10) were in the parvocellular layers, not because neurons in the magnocellular layers had the highest sensitivities. 4. Neurons with the smallest receptive-field centers, the highest spatial-frequency resolutions, and the highest optimal spatial frequencies were found in the parvocellular layers. However, the overall distributions of each of these properties overlapped substantially for neurons in the two types of layers, and the mean values were not significantly different. The mean high temporal-frequency cutoff was significantly higher for magnocellular than parvocellular neurons, but the difference was small (only 3 Hz), and it occurred because many parvocellular neurons had lower cutoffs than any seen in the magnocellular layers, not because magnocellular neurons had the highest temporal-frequency cutoffs. Parvocellular neurons also had narrower temporal-frequency tuning than magnocellular neurons. However, there was no significant difference in optimal temporal frequency.(ABSTRACT TRUNCATED AT 400 WORDS)
Multiple components of voltage-dependent potassium current in normal rat anterior pituitary cells
Authors: Herrington J. , Lingle C. J.
Published: December 2017

1. Voltage-dependent K+ currents were studied in normal rat anterior pituitary cells using the patch-clamp technique. To obtain cultures enriched for lactotrophs, density gradient centrifugation was performed on pituitary cells isolated from lactating rats. 2. Depolarizations to about -30 mV from a holding potential of -80 mV activate a rapidly inactivating [time constant (tau) approximately 15–20 ms at -20 mV]K+ current. This transient current activated at low voltages (termed IA) is abolished by 5 mM external 4-aminopyridine (4-AP) but is largely resistant to external tetraethylammonium (TEA) (< or = 30 mM). 3. Recovery from inactivation of IA is fast, with a tau of 100–200 ms at -80 mV. Deactivation is also fast (tau approximately 2.2 ms at -50 mV). The voltage of half-activation of IA is approximately -20 mV. The current is completely inactivated at a holding potential of -40 mV. 4. Voltage-dependent K+ current activated by depolarizations from a holding potential of -40 mV was first detectable at about -20 mV (high voltage-activated) and had a time course that varied among cells. 5. Deactivation of high voltage-activated K+ current was best described by the sum of two exponentials, with tau of about 3.7 and 30 ms at -50 mV. Both components reversed close to the equilibrium potential for K+. 6. The amplitudes of the two tail currents were independent of each other when variable-duration commands were used to activate current. The amplitude of the fast component was largest with 10- to 20-ms commands to +40 mV and was reduced (< or = 50%) with 136-ms commands. The slow component amplitude reached a peak by 40 ms and remained constant for commands < or = 136 ms at +40 mV. 7. The contribution of each component to the total high voltage-activated tail current was variable among cells, with the amount of fast component correlating with the amount of inactivation produced by commands to +40 mV. 8. The two components of tail current activated by depolarizations from the -40 mV holding potential were abolished by external TEA (10 mM). 4-AP (5 mM externally) selectively abolished the fast component of high voltage-activated tail current while only partially reducing the slow component. 9. These results suggest that normal rat anterior pituitary cells possess at least three distinct types of voltage-dependent K+ current: a low voltage-activated, transient current (IA) and two high voltage-activated currents.(ABSTRACT TRUNCATED AT 400 WORDS)
Regulation of glycine-insensitive desensitization of the NMDA receptor in outside-out patches
Authors: Tong G. , Jahr C. E.
Published: December 2017

1. Regulation of desensitization of N-methyl-D-aspartate (NMDA) receptors was studied in outside-out patches from cultured rat hippocampal neurons. The progressive increase in a glycine-insensitive form of desensitization after patch excision did not require extracellular Ca2+ concentration nor was it use dependent, but the initial extent of desensitization after patch formation was reduced by intracellular bis-(o-aminophenoxy)-N,N,N',N'-tetraacetic acid (BAPTA). 2. Preincubation of neurons with 30 microM dantrolene, which can decrease Ca2+ release from intracellular stores, also reduced the degree of NMDA receptor desensitization just after patch excision. Thus the development of this form of desensitization appears to be triggered by a transient increase of intracellular calcium. 3. The extent of glycine-insensitive desensitization was also reduced by intracellular ATP-gamma S, high concentrations of the phosphatase inhibitor, microcystin, or intracellular application of a peptide inhibitor of calcineurin. These data support the hypothesis that glycine-insensitive desensitization of the NMDA receptor in outside-out patches is regulated in part by the phosphorylation state of the receptor or an associated protein. 4. Because the NMDA channel is very permeable to Ca2+, the extent of phosphorylation and thus desensitization of the receptors may be sensitive to synaptic activation and could serve as a feedback mechanism to decrease the intensity of excitation and plasticity.
Neural basis for motor learning in the vestibuloocular reflex of primates. III. Computational and behavioral analysis of the sites of learning
Authors: Lisberger S. G.
Published: December 2017

1. We have used a combination of eye movement recordings and computer modeling to study long-term adaptive modification (motor learning) in the vestibuloocular reflex (VOR). The eye movement recordings place constraints on possible sites for motor learning. The computer model abides by these constraints, as well as constraints provided by data in previous papers, to formalize a new hypothesis about the sites of motor learning. The model was designed to reproduce as much of the existing neural and behavioral data as possible. 2. Motor learning was induced in monkeys by fitting them with spectacles that caused the gain of the VOR (eye speed divided by head speed) to increase to values > 1.6 or to decrease to values < 0.4. We elicited pursuit by providing ramp motion of a small target at 30 degrees/s along the horizontal axis. Changes in the gain of the VOR caused only small and inconsistent changes in the eye acceleration in the first 100 ms after the onset of pursuit and had no effect on the eye velocity during tracking of steady target motion. Electrical stimulation in the flocculus and ventral paraflocculus with single pulses or trains of pulses caused smooth eye movement toward the side of stimulation after latencies of 9–11 ms. Neither the latency, the peak eye velocity, nor the initial eye acceleration varied as a consistent function of the gain of the VOR. 3. The computer model contained nodes that represented position-vestibular-pause cells (PVP-cells) and flocculus target neurons (FTNs) in the vestibular nucleus, and horizontal gaze-velocity Purkinje cells (HGVP-cells) in the cerebellar flocculus and ventral paraflocculus. Node FTN represented only the “E-c FTNs,” which show increased firing for eye motion away from the side of recording. The transfer functions in the model included dynamic elements (filters) as well as static elements (summing junctions, gain elements, and time delays). Except for the transfer functions that converted visual motion inputs into commands for smooth eye movement, the model was linear. 4. The performance of the model was determined both by computer simulation and, for the VOR in the dark, by analytic solution of linear equations. For simulation, we adjusted the parameters by hand to match the output of the model to the eye velocity of monkeys and to match the activity of the relevant nodes in the model to the firing of HGVP-cells, FTNs, and PVP-cells when the gain of the VOR was 0.4, 1.0, and 1.6.(ABSTRACT TRUNCATED AT 400 WORDS)
Nonprimary auditory thalamic representation of acoustic change
Authors: Kraus N. , McGee T. , Littman T. , Nicol T. , King C.
Published: December 2017

1. The mismatch response, or mismatch negativity (MMN), is a neurophysiologic response to stimulus change. In humans and other animals, the MMN may underlie the ability to discriminate acoustic differences, a fundamental aspect of auditory perception. 2. This study investigated the role of the thalamus in the generation of a tone-evoked MMN in guinea pigs. Electrodes were placed in the caudomedial (nonprimary) and ventral (primary) subdivisions of the auditory thalamus (medial geniculate nucleus). Surface epidural electrodes were placed at the midline and over the temporal lobe. The MMN was elicited by a deviant stimulus (2,450-Hz tone burst) embedded in a sequence of standard stimuli (2,300-Hz tone bursts). 3. A tone-evoked MMN was present in nonprimary thalamus but was absent in the primary thalamus. Surface-recorded MMNs were measured at the midline but not over the temporal lobe. The correspondence between nonprimary thalamic responses and midline surface potentials, and between primary thalamic responses and temporal surface potentials, is consistent with data reported for the auditory middle latency responses in guinea pigs. 4. The results demonstrate that the nonprimary auditory thalamus contributes to the generation of a tone-evoked MMN in the guinea pig. Furthermore, the data indicate that the guinea pig is a feasible model for investigating central auditory processes underlying acoustic discrimination.
Developmental regulation of plasticity in cat somatosensory cortex
Authors: Juliano S. L. , Eslin D. E. , Tommerdahl M.
Published: December 2017

1. The neocortical response to deprivation of somatic sensory input in young animals of different ages was compared with the same manipulation in adults. The response was measured through the use of 2-deoxyglucose (2DG) mapping. Although several features of the cortical response were similar in animals of all ages, the metabolic patterns evoked by somatic stimulation differed substantially from each other at all ages. 2. When adult cats receive a digit amputation and survive from 2 to 8 wk, the pattern of stimulus-evoked metabolic uptake expands dramatically in the somatosensory cortex contralateral to the deprived forepaw. Comparisons between the normal and experimental somatosensory cortices reveal that the distribution of activity on the experimental side was roughly an expanded version of the normal pattern. 3. Unilateral digit amputations of digit 2 were conducted on kittens 2, 4, or 6 wk old. They survived until 3–4 mo and then received a 2DG experiment, during which digit 3 was stimulated bilaterally. Evaluation of the evoked metabolic pattern indicated substantial differences from the activity elicited in adults undergoing identical manipulations. 4. The individual patches of activity that made up the metabolic pattern were similar in intensity in both hemispheres when the digit amputation was conducted at either 2, 4, or 6 wk. After a digit amputation at 2 wk, the patches were significantly narrower in the experimental hemisphere; after a digit amputation at 6 wk, the patches were significantly wider in the hemisphere receiving from the deprived forepaw. 5. Two-dimensional maps of 2DG uptake in areas 3b and 1 of the somatosensory cortex reveal that after a digit amputation at 2, 4, or 6 wk, the distribution of activity in the hemisphere receiving from the digit amputation was more dispersed and widespread than in the normal hemisphere. The dispersed pattern of uptake was not an expanded version of the normal pattern, but scattered over a wider region of somatosensory cortex. This observation is similar to the normal pattern of evoked activity seen in developing animals. 6. The total area of 2DG uptake in the somatosensory cortex contralateral to a digit amputation conducted at 2 or 4 wk was not greater than that in the normal hemisphere, even though it was more widespread. After a digit amputation at 6 wk, however, the area of evoked activity was greater in the experimental hemisphere but not of the magnitude as the same manipulation in an adult.(ABSTRACT TRUNCATED AT 400 WORDS)
Projections from the pelvic nerve to the periphery of the cat's thalamic ventral posterolateral nucleus and adjacent regions of the posterior complex
Authors: Bruggemann J. , Vahle-Hinz C. , Kniffki K. D.
Published: December 2017

1. Mapping experiments were performed in the region of the ventral posterolateral nucleus of the lateral thalamus in pentobarbitone-anesthetized cats with the aim to locate foci with input from the electrically stimulated pelvic nerve. The locations of the recording sites were verified in Nissl-stained histological sections with reference to electrolytic lesions. 2. Of the 68 visceroceptive thalamic neurons identified, 63% were located in the periphery of the ventral posterolateral nucleus (VPLp) and 34% in the dorsal, lateral, and medial aspects of the posterior complex (POd, POl, and POm, respectively) directly adjacent to VPLp. The region surrounding the middle and caudal part of the ventral posterolateral nucleus (VPL) received a much denser input from the pelvic nerve than that around the rostral pole of VPL. 3. The response latencies of the thalamic neurons to pelvic nerve stimulation ranged from 10 to 65 ms (median: 16 ms; interquartile distance: 12–20 ms) indicating a transmission of information from the pelvic space via small and large diameter myelinated fibers. 4. Seventy-nine percent of the visceroceptive neurons tested (n = 58), in addition, had low threshold somatic receptive fields that were located in 67% of the cases in regions of the lower back, the thigh, the tail and/or the heel and in 26% of the cases on the hindfoot. None of the 40 visceroceptive neurons tested with noxious mechanical stimulation of the skin responded to this kind of stimulus.(ABSTRACT TRUNCATED AT 250 WORDS)
Incomplete suppressive effects of acetylsalicylic acid on the heat sensitization of canine testicular polymodal receptor activities
Authors: Mizumura K. , Sato J. , Minagawa M. , Kumazawa T.
Published: December 2017

1. Using canine testis-spermatic nerve preparations in vitro, we studied the effects of acetylsalicylic acid (ASA), an inhibitor of cyclooxygenase, on the polymodal receptor response to heat stimulation itself and on the sensitizing effects on the heat and bradykinin responses induced by strong heat stimulation (55 degrees C for 30 s). 2. Greater heat responses tended to be strongly suppressed by ASA (550 microM), with a significant correlation observed between the response magnitude and the magnitude of the suppression (r = 0.88 for the response at 45 degrees C; r = 0.83 for the response at 48 degrees C). The change in the heat response at 48 degrees C from 1.18 +/- 0.19 to 0.62 +/- 0.11 imp/s was statistically significant (n = 21, P < 0.01). 3. After stimulation at 55 degrees C in the presence of ASA, resting discharges at 34 degrees C appeared in only 2 of the 21 units tested. The responses at 45 and 48 degrees C, however, were significantly potentiated after this stimulation (those at 45 degrees C from 0.12 +/- 0.05 to 2.19 +/- 0.51 imp/s, mean +/- SE; those at 48 degrees C from 0.62 +/- 0.11 to 2.42 +/- 0.49 imp/s; P < 0.01, n = 21 for both). Sensitization was observed up to 50 min after stimulation at 55 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)
Excitatory stimulation during postsynaptic inhibition induces long-term depression in hippocampus in vivo
Authors: Thiels E. , Barrionuevo G. , Berger T. W.
Published: December 2017

1. As part of an effort to evaluate the biological plausibility of theoretically derived principles of synaptic modification, we studied activity-dependent long-term depression (LTD) of glutamatergic transmission in the hippocampus of anesthetized adult rats. Field potentials of CA1 pyramidal cells evoked by single-pulse stimulation (0.1 Hz) of the commissural afferents were recorded before and after paired-pulse stimulation (0.5 Hz) of the same pathway. A train of 150 or 200 paired pulses produced robust LTD of the commissural input to the CA1 pyramidal neurons when the interstimulus interval (ISI) of the pairs was short (25 ms) but not when the ISI was long (1,000 ms). 2. Paired-pulse stimulation with the short but not with the long ISI also was associated with pronounced inhibition of pyramidal cell firing upon the second pulse of a pair, despite the fact that the excitatory input was facilitated with the short-ISI paradigm. The inhibition of pyramidal cell activity was mediated by input to the pyramidal cells from local gamma-aminobutyric acid (GABA)-releasing interneurons activated by commissural fibers and/or CA1 recurrent collaterals, because the inhibition was eliminated by local administration of the selective GABAA receptor antagonist, bicuculline (50 microM), near the recording site. 3. Postsynaptic input from GABAergic interneurons was necessary for the induction of LTD, because short-ISI paired-pulse stimulation failed to produce LTD in the presence of bicuculline. 4. N-methyl-D-aspartate (NMDA) receptor-mediated excitation also was necessary for the induction of LTD, because administration of the selective NMDA receptor antagonist, D-2-amino-5-phosphonvaleric acid (100 microM), near the recording site prevented the development of LTD.(ABSTRACT TRUNCATED AT 250 WORDS)
Separation and identification of multiple potassium currents regulating the pacemaker activity of insect neurosecretory cells (DUM neurons)
Authors: Grolleau F. , Lapied B.
Published: December 2017

1. Whole cell voltage-clamp studies performed in isolated adult neurosecretory cells identified as dorsal unpaired median (DUM) neurons of the terminal abdominal ganglion of the cockroach Periplaneta americana have allowed us to reveal a complex voltage-dependent outward current regulating the pacemaker activity. 2. The global outward current remaining after tetrodotoxin treatment was activated by depolarization above -50 mV, showing steep voltage dependence and outward rectification. 3. We used tail current analysis to determine the ionic selectivity of this outward current. The reversal potentials for two extracellular potassium concentrations (-92.7 and -65.4 mV for 3.1 and 10 mM, respectively) is consistent with the expected equilibrium potential for potassium ions. 4. Both peak and sustained components of the global outward K+ current were reduced by external application of 20 mM tetraethylammonium chloride, 10 nM iberiotoxin, 1 nM charybdotoxin (CTX) and 1 mM cadmium chloride. Subtraction of current recorded in CTX solution from that in control solution revealed an unusual biphasic Ca(2+)-dependent K+ current. The fast transient current resistant to 5 mM 4-aminopyridine (4-AP) is distinguished by its dependence on holding potential and time course from the late sustained current. 5. In addition, two other components of CTX-resistant outward K+ current could be separated by sensitivity to 4-AP, time course, and voltage dependence. Beside a calcium-independent delayed outwardly rectifying current, a 4-AP-sensitive fast transient current resembling the A-current has been also identified. It activates at negative potential (about -65 mV) and unlike the A-current of other neurons, it inactivates rapidly with complex inactivation kinetics. A-like current is half-inactivated at -63.5 mV and half-activated at -35.6 mV. 6. Our findings demonstrate for the first time in DUM neuron cell bodies the existence of multiple potassium currents underlying the spontaneous electrical activity. Their identification and characterization represent a fundamental step in further understanding the pacemaker properties of these insect neurosecretory cells.
Alterations of visual climbing fiber response properties in cat cerebellar flocculus after cerebral cortical lesions
Authors: Sato Y. , Fushiki H. , Kawasaki T.
Published: December 2017

1. In the anesthetized decorticate cat, we recorded complex spike (CS) activity together with concomitant simple spike (SS) activity of the cerebellar flocculus (FL) Purkinje cells that responded to large-field visual pattern movement. The cerebral cortical contributions to the visual response characteristics were investigated by comparing the present results with the previous results of the anesthetized normal cat. 2. The direction-selective characteristics of the CS responses at a low (2 degrees/s) stimulus velocity are well preserved after the decortication. As in the normal cat, the cells are divided into two major types: the horizontal type that prefers horizontal stimuli and the vertical type that prefers vertical stimuli. The CS rate of the former increases during stimuli directed contralaterally to the recording site and decreases during ipsiversive stimuli, whereas that of the latter increases during upward stimuli and decreases during downward stimuli. Reciprocal properties of the CS and SS responses also are preserved: when the CS rate increases, the SS rate decreases and vice versa. 3. For both types, the CS modulation at high stimulus velocities is reduced after the decortication. The half-reduction of the average modulation occurs at approximately 100 degrees/s stimulus velocity compared with the modulation at 2 degrees/s in the normal cat, whereas it occurs at a lower velocity approximately 50 degrees/s in the decorticate cat. 4. For both types, the CS responses usually are driven through either eye in the normal cat. After the decortication, the CS modulation through the contralateral eye is reduced. 5. For both types, the receptive field of the ipsilateral eye extends into both visual hemifields in the normal cat. The CS responses through the contralateral visual hemifield are abolished, whereas those through the ipsilateral visual hemifield are preserved after the decortication. The CS modulation during stimuli restricted within a small central visual field (15 degrees x 15 degrees) projecting to the area centralis is prominent (approximately 70% of the full-screen response) in the normal cat and is sharply reduced (30%) after the decortication.(ABSTRACT TRUNCATED AT 400 WORDS)
Factors shaping the tone level sensitivity of single neurons in posterior field of cat auditory cortex
Authors: Phillips D. P. , Semple M. N. , Kitzes L. M.
Published: December 2017

1. The posterior field (field P) of the cat's auditory cortex contains a higher proportion of neurons whose response/level functions for characteristic frequency (CF) tones are nonmonotonic than does the primary field (AI). The general purpose of the present study is to assess whether the response/level functions of field P neurons are generated by the same mechanisms as those of cells in AI. All of the data came from single neurons in the cortices of barbiturate-anesthetized cats, to which we presented tonal stimuli through sealed, calibrated stimulating systems. 2. We obtained quantitative data from 123 neurons, of which 108 were located in field P. Of the 108 field P cells, 70% had nonmonotonic response/level functions for 5-ms rise time tones of CF. For cells of any given CF, both CF thresholds and best SPLs (i.e., SPLs associated with maximal responses) varied widely. A correlation analysis revealed that a linear relation between best SPL and CF threshold accounted for 73% of the data variance in the association between those response variables. An analysis of data from 83 nonmonotonic cells in AI revealed a similar relation. 3. Field P neurons whose response/level functions were non-monotonic for 5-ms rise time CF tones became even more narrowly tuned to SPL when the rise time of the tone bursts was reduced to 1 ms. Lengthening the rise time to 20 ms reduced or eliminated the SPL tuning in almost all of these neurons. The general form of monotonic tone response/level functions was commonly unaffected by variation in signal rise time. In a few instances, cells with monotonic response/level functions for 5- and 20-ms rise time tones developed nonmonotonic functions for 1-ms rise time tones. 4. Field P neurons with nonmonotonic response/level functions for CF tones usually failed to respond to wideband noise pulses, or, less commonly, responded to noise only at low SPLs. In contrast, field P cells with a monotonic response to CF tones usually responded monotonically to noise. 5. The minimal mean first-spike latencies of field P neurons were generally longer than those of AI cells studied under similar conditions. The precision of first-spike timing, measured using the SD of the mean first-spike latency, was commonly poorer than that of AI cells. 6. The properties of field P cells followed the same rules as those seen in AI.(ABSTRACT TRUNCATED AT 400 WORDS)
Hysteresis reduction in proprioception using presynaptic shunting inhibition
Authors: Hatsopoulos N. G. , Burrows M. , Laurent G.
Published: December 2017

1. The tonic responses of angular-position-sensitive afferents in the metathoracic chordotonal organ of the locust leg exhibit much hysteresis. For a given joint angle, the ratio of an afferent's tonic firing rate after extension to its firing rate after flexion (or vice versa) is typically between 1.2:1 and 3:1 but can be as large as 10:1. Spiking local interneurons, that receive direct inputs from these afferents, can, by contrast, exhibit much less hysteresis (between 1.1:1 and 1.2:1). We tested the hypothesis that presynaptic inhibitory interactions between afferent axons reduces the hysteresis of postsynaptic interneurons by acting as an automatic gain control mechanism. 2. We used two kinds of neural models to test this hypothesis: 1) an abstract nonspiking neural model in which a multiplicative, shunting term reduced the "firing rate" of the afferent and 2) a more realistic compartmental model in which shunting inhibition presynaptically attenuated the amplitude of the action potentials reaching the afferent terminals. 3. The abstract neural model demonstrated the automatic gain control capability of a network of laterally inhibited afferent units. A postsynaptic unit, which was connected to the competitive network of afferents, coded for joint angle without saturating as the strength of the afferent input increased by two orders of magnitude. This was possible because shunting inhibition exactly balanced the increase in the excitatory input. This compensatory mechanism required the sum of the excitatory and inhibitory conductances to be much larger than the leak conductance. This requirement suggested a graded weighting scheme in which the afferent recruited first (i.e., at a small joint angle) received the largest inhibition from each of the other afferents because of the lack of active neighbors, and the afferent recruited last (i.e., at a large joint angle) received the least inhibition because all the other afferents were active. 4. The compartmental model demonstrated that presynaptic shunting inhibition between afferents could decrease the average synaptic conductance caused by the afferents onto the spiking interneuron, thereby counterbalancing the afferents' large average firing rates after movements in the preferred direction. Therefore the total postsynaptic input per unit time did not differ much between the preferred and nonpreferred directions.(ABSTRACT TRUNCATED AT 400 WORDS)
Serotonergic modulation of locust motor neurons
Authors: Parker D.
Published: December 2017

1. The effects of the putative endogenous neuromodulator serotonin (5-HT) on the fast extensor and flexor tibiae motor neurons in the locust (Schistocerca gregaria) metathoracic ganglion, were analyzed. 2. 5-HT consistently increased the duration of the fast extensor spike and usually reduced the afterhyperpolarization, although this effect was less consistent. The spike broadening in the fast extensor was associated with an increase in the amplitude of the excitatory postsynaptic potential (EPSP) evoked monosynaptically in the flexor motor neurons by fast extensor stimulation. 5-HT also increased the membrane resistance of the fast extensor and flexor tibiae motor neurons. 3. The effects of 5-HT were mimicked by bath application of the 5-HT uptake inhibitor imipramine, and blocked by the 5-HT receptor antagonist ketanserin. The effects were also mimicked by dibutryl cyclic AMP, a membrane permeant analogue of cyclic AMP, and by the phosphodiesterase inhibitor 3-isobutyl-1-methyl-xanthine, but not by dibutryl cyclic GMP. The 5-HT-dependent modulation was blocked by the protein kinase A inhibitor H8. In addition, injection of cyclic AMP into the fast extensor or a flexor motor neuron could mimic the effects of 5-HT on these neurons. 4. 5-HT probably broadened the FETi action potential by modulating potassium conductances responsible for spike repolarization. 5. These results show that 5-HT modulates both the fast extensor and flexor tibiae motor neurons, resulting in potentiation of synaptic transmission between these neurons. In addition, the increase in flexor membrane resistance will potentiate other inputs onto these cells, which will affect the output of the motor neurons during locomotion.
Calcium hyperexcitability in neurons cultured with glutamate receptor blockade
Authors: Obrietan K. , Van den Pol A. N.
Published: December 2017

1. The effects of culturing hypothalamic neurons in glutamate receptor antagonists were studied with fura-2 Ca2+ digital imaging of groups of synaptically coupled neurons. Removal of D-2-amino-5-phosphonovalerate (AP5) and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) from cultures chronically blocked for periods of 14-188 days caused a dramatic increase in neuronal Ca2+ to abnormally high levels 5- to- 10 fold greater than the normal intracellular levels of 50-100 nM. In most cases AP5/CNQX removal initiated spontaneous synchronized Ca2+ oscillations. 2. Ca2+ rises and oscillations were blocked by the reintroduction of AP5/CNQX or by the addition of tetrodotoxin to block action potentials. These data indicate that hypothalamic neurons were the source of the excitatory transmitter that activated glutamate receptors and consequently led to the Ca2+ hyperexcitability. 3. The Ca2+ spike amplitude and frequency increased in response to the removal of Mg2+ from the perfusion solution to facilitate N-methyl-D-aspartate (NMDA) receptor responses. Picrotoxin, a GABAA-receptor blocker, also increased Ca2+ activity. 4. Blocking either NMDA (with AP5) or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate-type (with CNQX) glutamate receptors reduced the level of Ca2+, but blocking both types was necessary for chronically blocked neurons to return to their basal Ca2+ level. 5. The survival of a large percentage of chronically blocked neurons was dependent on the presence of glutamate receptor blockade. Removal of AP5/CNQX from the tissue culture medium induced an immediate increase in Ca2+ levels in the majority of chronically blocked neurons and, with prolonged withdrawal of AP5/CNQX (3 h), 50% of the neurons lost the immediate ability to regulate internal Ca2+ levels. Excitotoxic cell death was induced in 40% of the neurons within 40 h of the removal of AP5/CNQX from neurons chronically blocked for 30 days. The number of neurons that survived for 70 days doubled when cultures were maintained in AP5/CNQX. 6. Relative to control cultures of the same period in vitro, chronically blocked neurons showed an enhanced Ca2+ influx when stimulated with the glutamate receptor agonists kainate (+70%), NMDA (+62%), or glutamate (+34%) in the presence of tetrodoxin. When the data from control and chronically blocked cultures stimulated with glutamate receptor agonists were pooled, without exception all the smallest responses were found in the control neurons. Compared with controls, chronically blocked neurons showed an exaggerated response to glutamate in the presence of nimodipine, indicating that Ca2+ hyperexcitability was not due to changes in voltage activated L-type Ca2+ channels.(ABSTRACT TRUNCATED AT 400 WORDS)
Altered thermal responsiveness during regeneration of corneal cold fibers
Authors: Tanelian D. L. , Monroe S.
Published: December 2017

1. To date, there has been no quantitative, systematic, study of the electrophysiology of regenerating cold receptors. This study, therefore, examines the changes in cold-receptor neural activity following a circular wound (5 mm dia, 200 microns deep) on the surface of the rabbit cornea. This is a well studied wounding model, in which neural regeneration has been anatomically quantified. 2. Extracellular recordings were obtained from a total of 90 single cold fibers, at 1, 3, 10, 20, or 30 days following wounding. The adapting temperature was 35 degrees C in all experiments. Thermal sensitivity for each fiber was determined by using a series of temperature steps, 0.2 degree C ranging from 35 to 34 degrees C, and 2 degrees C steps ranging from 35 to 24 degrees C. The rate of temperature change ranged from 0.2 to 1 degree C/s. 3. At the adapting temperature, the tonic activity of the regenerating cold-fibers was not significantly different from normals. Conduction velocities for regenerating cold-fibers were slower on day 1 postwounding compared with normal fibers, 0.59 +/- 0.04 and 0.75 +/- 0.04 (SE) M/s, respectively, however, were within the normal range by day 30 postwounding, 0.72 +/- 0.06 M/s. 4. On day 1, sprouting fibers showed decreased responsiveness to cooling (P < 0.05). At days 3 and 10 postwounding, action potential rates in response to cooling were enhanced by 180-200% of normal (P < 0.05) and returned to preinjury values by 20 to 30 days postwounding.(ABSTRACT TRUNCATED AT 250 WORDS)
Midbrain suppression of limb withdrawal and tail flick reflexes in the rat: correlates with descending inhibition of sacral spinal neurons
Authors: Carstens E. , Douglass D. K.
Published: December 2017

1. The aim of this study was to utilize new quantitative behavioral methods in rats to investigate the effects of electrical stimulation in midbrain analgesia areas on the magnitude of flexion hindlimb withdrawal and tail flick reflexes evoked by graded noxious heating. Electrophysiological experiments were then done with the use of these animals to correlate behavioral data with the effects of identical midbrain stimulation on sacral dorsal horn neuronal responses to graded heating of the tail. 2. To quantify limb withdrawals, electromyographs (EMGs) were recorded in biceps femoris during withdrawals elicited by noxious heat stimuli (40-52 degrees C, 5 s, 2-min intervals) delivered to the plantar surface of the hind paw, without and during concomitant electrical stimulation (100 ms, 100-Hz trains, 3/s, 10-600 microA) in midbrain periaqueductal gray (PAG) or laterally adjacent reticular formation (LRF) via previously implanted electrodes. The same animals were tested with the use of a tail flick paradigm modified to allow measurement of the force of tail movements in three orthogonal planes and thereby calculate the overall force vector of tail flicks elicited by graded noxious radiant heat pulses (38-58 degrees C, 5 s, 2-min intervals) delivered to the tail, again with and without concomitant PAG or LRF stimulation. Finally, the same rats were anesthetized with pentobarbital sodium and microelectrode recordings made from single sacral dorsal horn neurons responsive to the same noxious heat stimuli delivered to the tail to assess effects of PAG and LRF stimulation. 3. PAG and LRF stimulation suppressed the magnitude of limb flexor EMGs, and tail flick force vectors, in an intensity-dependent manner. Recruitment of suppression of both limb withdrawal EMGs and tail flicks was generally more effective for LRF compared with PAG stimulation, although mean thresholds for suppression were similar. Tail flick force and limb withdrawal EMGs recorded from the same rat in separate sessions were suppressed about equally in a majority of cases. 4. Limb withdrawal EMG magnitude increased monotonically from threshold (approximately 40 degrees C) to 52 degrees C. The population stimulus-response function was fit equally well by linear regression or a 2 degrees polynomial function (r2 = 0.79 for both). PAG stimulation significantly reduced the mean slope of the stimulus-response function (to 73%; n = 15), whereas LRF stimulation shifted it toward the right with a smaller slope reduction (to 85%) and 3 degrees C increase in threshold.(ABSTRACT TRUNCATED AT 400 WORDS)