bluuebunny/crossref_metadata_2025 huggingface dataset:
Na(+)-activated nonselective cation channels in primary olfactory neurons
Authors: Zhainazarov A. B. , Ache B. W.
Published: December 2017

1. Excised inside-out patch recordings were used to describe a novel cation channel from cultured lobster olfactory receptor neurons that is activated by [Na+]i. 2. The channel is reversibly activated by intracellular Na+ as low as 5 mM. The half-effect concentration of intracellular Na+ is approximately 60 mM at -60 mV. The dependence of the channel open probability on [Na+]i is sigmoidal with a Hill coefficient of 3.1, indicating that more than one Na+ must bind to activate the channel. 3. The channel is equally permeable to Na+, K+, and Li+. In symmetrical 210 mM Na+, the open channel current-voltage relationship shows slight inward rectification at positive potentials. The slope conductance of the channel is 107 pS between -90 and 0 mV. 4. Although the channel is not activated by voltage in the absence of intracellular Na+, the gating of the channel is dependent on voltage as well as [Na+]i and [Na+]o. 5. Both intracellular Ca2+ and Mg2+ reversibly affect channel activity in a concentration-dependent manner starting at 1 microM. Ca2+ decreases both the open probability and the single channel amplitude, whereas Mg2+ decreases the open probability but has no effect on the single channel amplitude. Ba2+ (5 mM), but not 20 mM Cs+ and 100 microM amiloride, reversibly block the channel. 6. We speculate that this novel cation channel regulates neuronal excitability by accentuating the rate and/or the magnitude of depolarization of the cell to odors.
Dynamics of neurons controlling movements of a locust hind leg: Wiener kernel analysis of the responses of proprioceptive afferents
Authors: Kondoh Y. , Okuma J. , Newland P. L.
Published: December 2017

1. The response properties of proprioceptive sensory neurons providing input to the local circuits controlling leg movements of the locust have been analysed by the Wiener kernel method. The proprioceptor, the femoral chordotonal organ, encodes the position and movements of the tibia about the femorotibial joint. 2. Intracellular recordings were made from sensory neurons while the apodeme of the organ was moved with a band-limited Gaussian white noise signal with a cutoff frequency of 27, 58, or 117 Hz. To define the input-output characteristics of the neurons, the first- and second-order Wiener kernels were computed by a cross-correlation between the spike response of the afferents and the white noise stimulus. 3. White noise stimulation elicited sustained spiking in 50 out of 54 afferents throughout the 20 s periods of stimulation and recording. The first-order kernels, the linear response properties, of these afferents were of six basic types that were dependent on the cutoff frequency of the white noise stimulus. These included 1) flexion-sensitive afferents that were primarily position sensitive irrespective of stimulus frequency, 2) flexion-sensitive afferents that were position sensitive at low frequencies but also coded velocity at higher frequencies, 3) flexion-sensitive afferents that coded velocity at all stimulus frequencies, 4) flexion-sensitive afferents that coded velocity at low stimulus frequencies but also acceleration at high frequencies, 5) extension-sensitive afferents that coded velocity at all stimulus frequencies, and 6) extension-sensitive afferents that coded velocity at low stimulus frequencies and acceleration at high frequencies. A seventh type contained the four remaining afferents that adapted rapidly to the stimulus within 3-5 s. These were all extension-acceleration sensitive irrespective of stimulus frequency. 4. The gain curves (produced by Fourier transform of the 1st-order kernels) and the power spectra of the linear models (produced by convolving the 1st-order kernels with the white noise) demonstrated that responses in the position-sensitive afferents are representative of a constant gain low-pass filter with a cutoff frequency of approximately 80 Hz, whereas those in the velocity- and acceleration-sensitive afferents are band passed, having peaks at 80 Hz. 5. The main nonlinearity was a signal compression in which the diagonal peak(s) of the second-order nonlinear kernels offset one or more peaks of the first-order kernels and represents a rectification or directional sensitivity of the afferents.(ABSTRACT TRUNCATED AT 400 WORDS)
Regional distribution of rat electroolfactogram
Authors: Ezeh P. I. , Davis L. M. , Scott J. W.
Published: December 2017

1. Electroolfactorgram (EOG) recordings were made from different regions of the rat olfactory epithelium to test for spatial distribution of odor responses. 2. The EOG recordings showed spatial distribution of the odor responses in the olfactory epithelium. While some odorants (amyl acetate, anisole, and ethyl butyrate) were more effective in evoking responses in the dorsal recess near the septum, other odorants (including limonene, cineole, cyclooctane, and hexane) were more effective in the lateral recesses among the turbinate bones. These differences were seen as statistically significant odorant-by-position interactions in analysis of variance. 3. Comparisons of recordings along the anteroposterior dimension of the epithelium produced smaller differences between the odor responses. These were not significant for 3-mm distances, but were statistically significant for 5- to 6-mm distances along the dorsomedial epithelium. 4. The latencies were significantly longer in the lateral recesses than in the medial region. This probably reflects a more tortuous air path along the turbinate bones to the lateral recesses. 5. The olfactory receptor cells were activated by antidromic stimulation via the nerve layer of the olfactory bulb. The population spikes evoked from the olfactory receptor cells could be suppressed by prior stimulation with odorants that evoked strong EOG responses. This collision of the antidromic action potentials with the odor-evoked action potentials indicates that the same population of receptor cells was activated in both cases. 6. The flow rate and duration of the artificial sniff were varied systematically in some experiments. The differential distribution of response sizes was present at all flow rates and sniff durations. Some odors (e.g., amyl acetate and anisole) produced increased responses in the epithelium of the lateral recesses when flow rates or sniff durations were high. We suggest that these changes may reflect the sorptive properties of the nasal membranes on these odors. The responses to other odors (e.g., hexane or limonene) were not greatly affected by flow rate or sniff duration. 7. Taken with existing anatomic data, the results indicate that the primary olfactory neurons that project axons to glomeruli in different parts of the olfactory bulb are responsive to different odors. The latency differences between responses at medial and lateral sites are large enough to be physiologically significant in the generation of the patterned responses of olfactory bulb neurons.
Saccade-related activity in monkey superior colliculus. I. Characteristics of burst and buildup cells
Authors: Munoz D. P. , Wurtz R. H.
Published: December 2017

1. In the monkey superior colliculus (SC), the activity of most saccade-related neurons studied so far consists of a burst of activity in a population of cells at one place on the SC movement map. In contrast, recent experiments in the cat have described saccade-related activity as a slow increase in discharge before saccades followed by a hill of activity moving across the SC map. In order to explore this striking difference in the distribution of activity across the SC, we recorded from all saccade-related neurons that we encountered in microelectrode penetrations through the monkey SC and placed them in categories according to their activity during the generation of saccades. 2. When we considered the activity preceding the onset of the saccade, we could divide the cells into two categories. Cells with burst activity had a high-frequency discharge just before saccade onset but little activity between the signal to make a saccade and saccade onset. About two thirds of the saccade-related cells had only a burst of activity. Cells with a buildup of activity began to discharge at a low frequency after the signal to make a saccade and the discharge continued until generation of the saccade. About one third of the saccade-related cells studied had a buildup of activity, and about three fourths of these cells also gave a burst of activity with the saccade in addition to the slow buildup of activity. 3. The buildup of activity seemed to be more closely related to preparation to make a saccade than to the generation of the saccade. The buildup developed even in cases when no saccade occurred. 4. The falling phase of the discharge of these saccade-related cells stopped with the end of the saccade (a clipped discharge), shortly after the end of the saccade (partially clipped), or long after the end of the saccade (unclipped). 5. Some cells had closed movement fields in which saccades that were substantially smaller or larger than the optimal amplitude were not associated with increased activity. Other cells tended to have open-ended movement fields without any peripheral border; they were active for all saccades of optimal direction whose amplitudes were equal to or greater than a given amplitude.(ABSTRACT TRUNCATED AT 400 WORDS)
Mnemonic firing of neurons in the monkey temporal pole during a visual recognition memory task
Authors: Nakamura K. , Kubota K.
Published: December 2017

1. We examined single-neuronal activity in the temporal pole of monkeys, including the anterior ventromedial temporal (VMT) cortex (the temporopolar cortex, area 36, area 35, and the entorhinal cortex) and the anterior inferotemporal (IT) cortex, during a visual recognition memory task. In the task, a trial began when the monkey pressed a lever. After a waiting period, a visual sample stimulus (S) was presented one to four times on a monitor with an interstimulus delay. Thereafter, a new stimulus (R) was presented. The monkeys were trained to remember S during the delay period and to release the lever in response to R. Colored photographs of natural objects were used as visual stimuli. 2. About 70% of the recorded neurons (225 of 311) responded to at least one of the Ss tested. Thirty percent of these neurons (68 of 225) continued to fire during the subsequent delay periods. In 75% of these neurons (51 of 68), the firing during the delay period strongly correlated with the response to S. 3. The discharge rate during the delay period did not correlate with the monkey's eye movements, pressing or releasing of the lever, or the reaction time. 4. If the monkey erroneously released the lever in response to S or during the delay period, the firing disappeared after the erroneous lever release. If the monkey failed to release the lever in response to R, the firing persisted even after R was withdrawn. The discharge rate in incorrect trials was comparable with that in correct trials. The neurons were considered to fire for as long as the memory of S was necessary. 5. Firing persisted even when an achromatic version or half (even a portion) of S was presented, indicating that the color, a particular portion, or the entire shape of S was not always necessary to elicit firing. 6. An S that elicited firing during the delay period invariably elicited a visual response. Neurons that fired during the delay period showed a higher stimulus selectivity than other visually responsive neurons in the anterior VMT cortex. Thus neurons that fire during the delay period represent a subgroup of visually responsive neurons that are selectively tuned to a certain stimulus. 7. More neurons fired during the delay period in the anterior VMT cortex than in the anterior IT cortex. 8. We conclude that firing during the delay period by neurons in the temporal pole reflects the short-term storage of visual information regarding a particular S.
Preferential correlations of a medullary neuron's activity to different sympathetic outflows as revealed by partial coherence analysis
Authors: Cohen M. I. , Yu Q. , Huang W. X.
Published: December 2017

1. In vagotomized, paralyzed, decerebrate cats, simultaneous recordings were taken from one or more sympathetic nerves [cervical sympathetic (CS), inferior cardiac (IC), splanchnic (SP)] and from medullary neurons in vasomotor-related regions. Coherence analyses were used to ascertain the presence of sympathetic rhythms (2-6 Hz or "3-Hz rhythm," 7-13 Hz or "10-Hz rhythm") that were correlated between different signals. The occurrence of a significant peak at such a frequency in a unit-nerve coherence spectrum allowed the identification of a medullary neuron as sympathetic related. 2. A serendipitous example is given of a rostral ventrolateral medullary neuron that had significant unit-nerve 10-Hz coherence peaks for three sympathetic nerves (CS, IC, SP); but, as revealed by partial coherence analysis, the unit activity's correlation with one nerve's activity could be partially or completely dependent on its correlation with other nerve activities. Thus in this case the unit-CS and unit-IC coherences at 10 Hz were completely dependent on the SP rhythm, whereas the unit-SP coherence was not significantly affected by the CS and IC rhythms. This asymmetry suggests that the neuron was preferentially connected to SP-generating medullary circuits. 3. This example indicates the strength of partial coherence analysis as a means of studying differential connectivity between medullary sympathetic-related neurons and sympathetic output neuron populations.
Fast imaging of [Ca]i reveals presence of voltage-gated calcium channels in dendritic spines of cultured hippocampal neurons
Authors: Segal M.
Published: December 2017

1. Cultured hippocampal neurons were recorded with a patch pipette containing 100 microM of the calcium indicator Fluo-3, and one of their dendrites, carrying dendritic spines, was visualized with a x100, 1.3-numerical aperture oil objective. Calcium spikes evoked by depolarizing the somata and changes in free dendrite and spine calcium concentrations ([Ca]d and [Ca]s, respectively) were monitored with a cooled charge-coupled device (CCD) camera, acquiring images at a rate of 17-20 ms per frame. In the majority of spine-dendrite pairs, [Ca]s rose faster and to a higher level than the adjacent [Ca]d. Likewise, topical application of glutamate evoked a faster and larger change in [Ca]s than in [Ca]d. The rise of intracellular calcium concentration in response to a depolarizing current pulse, but not in response to glutamate, was reduced in the presence of the calcium antagonist verapamil in both dendrites and spines. It is suggested that dendritic spines possess voltage-gated calcium channels.
Activity of neurons in the medial pontomedullary reticular formation during orienting movements in alert head-free cats
Authors: Isa T. , Naito K.
Published: December 2017

1. Single unit activities of 236 neurons were recorded in the medial pontomedullary reticular formation during visually triggered orienting gaze shifts in 10 alert cats under head-free conditions using movable tungsten-needle electrodes attached to the skull. The activities were analyzed mainly in relation to the head movement that was triggered by presentation of a light-emitting diode (LED) in one of eight directions separated radially by 45 deg after fixation of the center LED. Of these, 120 neurons were recorded in the pontine reticular formation, chiefly in the nucleus reticularis pontis caudalis, and the remaining 116 were in the medullary reticular formation, chiefly in the nucleus reticularis gigantocellularis. Activities of 65 pontine and 65 medullary neurons were modulated in relation to the dynamic phase of orienting movements ("orienting-related neurons"). Activities of the remaining neurons were modulated either irregularly or not at all during orienting movement ("irregular or no-response neurons"). Input from the contralateral superior colliculus and cerebral cortex and projections to the spinal cord were also investigated. 2. Among the orienting-related neurons, 62 pontine and 55 medullary neurons showed increases in activity preceding the onset of eye and head movement by 0-155 ms ("pretype"). Three pontine and 10 medullary neurons showed increases in activity only after the onset of movement ("posttype"). Of the pretype neurons, 61 pontine and 51 medullary neurons showed directional preference of activity ("directional" neurons). One pontine and four medullary neurons were classified as "omnidirectional" because these neurons increased activity preceding movements in all directions tested, and no directional preference was apparent. 3. In the pretype-directional cells, the average firing frequency during bursts was correlated with amplitude and angular velocity of head movements. Activities of the directional neurons during movements in the eight different directions could be well fitted with cosine functions in the majority of cases. The preferred directions of most pontine neurons and of about half the medullary neurons, as determined by first-degree sinusoidal regression analysis, were distributed around the ipsiversive horizontal axis. However, there were also a considerable number of neurons whose preferred directions were upward, downward, contraversive, or oblique in the medulla. 4. Among the directional cells preferring ipsiversive horizontal movements, 11 pontine neurons showed activity, the onset of which was locked to visual stimuli with latencies of 40-70 ms, in addition to phasic discharges locked to the onset of movement. This "stimulus-locked activity" was sometimes modulated depending on the attentional state of the animal.(ABSTRACT TRUNCATED AT 400 WORDS)
Depression of synaptic connections between identified motor neurons in the locust
Authors: Parker D.
Published: December 2017

1. The fast extensor tibiae motor neuron makes direct excitatory central connections with the posterior group of flexor tibiae motor neurons in the locust metathoracic ganglion. The flexor group has a slow, a fast, and an intermediate motor neuron. The motor neurons are involved in the motor program for kicking and jumping, the defensive and escape behaviors of the locust. An antidromic action potential in fast extensor tibiae motor neuron (FETi) results in a monosynaptic, glutamatergic excitatory postsynaptic potential (EPSP) in each of the flexor motor neurons. 2. A train of 10 antidromic spikes in FETi at frequencies of 1<20 Hz resulted in depression of the amplitude of the EPSP in each of the flexor motor neurons. The depression was not significantly different in the different flexor motor neurons. The depression was greater with higher frequency stimulation and was reduced in low calcium saline. 3. After stimulation at 20 Hz, the EPSP amplitude was depressed by approximately 80%. This did not change when the number of stimuli was increased to 20, when stimulation was done in high calcium saline, or when the frequency of stimulation was increased to 50 or 100 Hz. The recovery from depression was greater after 20-Hz stimulation than at lower frequencies, although the recovery was reduced when the number of stimuli was increased, and also in high calcium saline. 4. In normal saline the depression of the EPSP amplitude was associated with a reduction of the presynaptic spike amplitude at frequencies of > or = 5 Hz. In tetraethylammonium (TEA) saline the width of a TEA-broadened spike was also reduced. The reduction in spike amplitude and spike width correlated with the depression of the EPSP. 5. Certain of these results are consistent with a depletion model of synaptic depression, whereas others are not consistent with this model. The depression may be partly due to an initial depletion of transmitter stores, and partly to modulation of the presynaptic action potential that reduces calcium entry, and therefore transmitter release. The significance of the depression on the motor program for kicking and jumping is discussed.
Involvement of cochlear efferent pathways in protective effects elicited with binaural loud sound exposure in cats
Authors: Rajan R.
Published: December 2017

1. Studies in guinea pigs have shown that the crossed olivocochlear efferent [crossed olivocochlear bundle (OCB)] pathways can reduce the cochlear neural desensitization caused by loud sounds. In one experimental paradigm, binaural loud sound exposure produced less damage than did monaural exposure, and various tests confirmed that this could be attributed to the OCB. In contrast, a study in cats has shown no such protection from the OCB for binaural exposures. There are some methodological differences between the cat and guinea pig studies that could account for the difference. The present study was carried out to determine whether two factors, namely anesthetic or exposure frequency, could account for the difference. Experiments were carried out in cats using barbiturate anesthesia, as in the guinea pig experiments. 2. Using a unilateral middle ear muscle (MEM) tenotomy, it was confirmed that under Nembutal anesthesia the MEM did not affect the threshold losses to monaural or binaural exposure. However, comparing results for monaural versus binaural 11-kHz exposures, there were significantly less threshold losses to the binaural exposure, independent of the presence of the MEM. No such difference between monaural and binaural exposures was seen for 3-kHz exposures. 3. By employing unilateral surgical strategies such as MEM tenotomy and/or various brain stem incisions, it was confirmed that the protection with binaural compared with monaural 11-kHz exposure was due specifically to the OCB. In unilaterally deefferented animals, binaural 11-kHz exposure always produced lower threshold losses on the OCB-intact side than on the OCB-cut side, regardless of the status of the MEM. Brain stem cuts that affected other rostrally or laterally located structures but not the OCB produced similar threshold losses bilaterally after binaural exposure, and the losses were comparable with the protected levels seen in other cases with intact OCB and binaural exposure. These data confirmed that when using an exposure frequency very similar to that used in the guinea pig experiments, a protective OCB effect could be demonstrated in cats, as previously seen in guinea pigs. The MEMs appeared to be inactive in barbiturate-anesthetized animals and were not activated by 3-, 7-, or 11-kHz exposures at 100 dB SPL for 10 min. The companion manuscript demonstrates this same effect across a wider range of exposures.(ABSTRACT TRUNCATED AT 400 WORDS)
Frequency and loss dependence of the protective effects of the olivocochlear pathways in cats
Authors: Rajan R.
Published: December 2017

1. In the previous manuscript I suggested a frequency dependency to olivocochlear bundle (OCB)-mediated protection from loud sound by showing protection for binaural compared with monaural 11-kHz exposures but not 3-kHz exposures of the same intensity and duration. To determine whether this was the case, experiments were carried out in barbiturate-anesthetized cats using the paradigm of a unilateral brain stem incision to deefferent one cochlea in each animal before presentation of a binaural loud sound exposure. With equal-intensity, equal-duration binaural exposures, in different groups protection in OCB-intact compared with OCB-cut ears was seen only for exposures at 11, 15, or 20 kHz, but not at 3 or 7 kHz, suggesting that OCB-mediated protection was found only for higher-frequency exposures. This would be consistent with the OCB-mediated protection in guinea pig studies where 10-kHz exposures were used and its absence in a study in cats where 6-kHz exposures were used. However, this conclusion had to be qualified by the fact that the lower-frequency exposures resulted in smaller threshold losses than did the higher-frequency exposures. 2. To determine whether OCB-mediated protection could be obtained for lower-frequency exposures that were made as damaging as or more damaging than the high-frequency exposures, longer-duration, lower-frequency exposures were used. OCB-mediated protection could then be obtained for exposure at 7 kHz, 100 dB SPL for 15 min but not at 3 or 5 kHz, 100 dB SPL for 20 min or at 3 kHz, 100 dB SPL for 40 min or 106 dB SPL for 20 min. Finally, when large threshold losses were produced with exposure at 3 kHz, 106 dB SPL for 40 min, OCB-mediated protection could be obtained for this low-frequency exposure too. These effects suggested that there were different “activation threshold” for OCB-mediated protection as a function of exposure frequency. To determine whether this also applied for the higher-frequency exposures (11, 15, and 20 kHz), all of which had elicited OCB-mediated protection when presented at 100 dB SPL for 10 min, these exposure frequencies were presented at 100 dB SPL for 7 min to produce low threshold losses. Now protection was found for the 11- and 15-kHz exposures but not for the 20-kHz exposure. 3. Thus the activation threshold for OCB-mediated protection varied in a frequency-dependent manner.(ABSTRACT TRUNCATED AT 400 WORDS)
Role of metabotropic glutamate receptor subtypes in the patterning of epileptiform activities in vitro
Authors: Merlin L. R. , Taylor G. W. , Wong R. K.
Published: December 2017

1. Epileptiform activities were elicited from the in vitro guinea pig hippocampus by the addition of picrotoxin. Modification of the picrotoxin-induced activities by agents active at metabotropic glutamate receptors (mGluRs) was examined using intracellular and extracellular recordings. 2. Picrotoxin typically elicited synchronized discharges (epileptiform bursts) in CA3 neurons. These spontaneously occurred at regular intervals. In the presence of (+)-alpha-methyl-4-carboxyphenylglycine (MCPG; 700–1,000 microM), an antagonist at multiple mGluR subtypes, the frequency of spontaneous epileptiform bursts decreased. In contrast, when the mGluR agonists (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD; 5 microM) or (2S,3S,4S)-alpha-(carboxycyclopropyl)-glycine (L-CCG-I; 10 microM) were added to the incubating medium, the frequency of epileptiform bursts increased. No consistent change in membrane potential, burst duration, nor burst afterhyperpolarization was associated with the changes in burst frequency. 3. When spontaneous burst frequency was reduced in MCPG, stimulation at a higher frequency entrained bursts without failure. Bursts evoked in MCPG were similar in waveform and amplitude to those evoked in the control state. 4. (S)-4-carboxyphenylglycine (S-4CPG) and (R,S)-4-carboxy-3-hydroxyphenylglycine (RS-4C3HPG) are antagonists at mGluR subtypes 1 and 5 but agonists at mGluRs 2 and 3. Addition of either of these agents increased the frequency of epileptiform bursts. 5. These results suggest that sufficient glutamate is released during epileptiform activities to activate mGluRs. The overall effect is to increase the frequency of synchronized discharges. This modulatory action on burst frequency is probably mediated via the mGluR 2 and 3 receptor subclass.
Pruning of rat cortical taste neurons by an artificial neural network model
Authors: Nagai T. , Katayama H. , Aihara K. , Yamamoto T.
Published: December 2017

1. Taste qualities are believed to be coded in the activity of ensembles of taste neurons. However, it is not clear whether all neurons are equally responsible for coding. To clarify the point, the relative contribution of each taste neuron to coding needs to be assessed. 2. We constructed simple three-layer neural networks with input units representing cortical taste neurons of the rat. The networks were trained by the back-propagation learning algorithm to classify the neural response patterns to the basic taste stimuli (sucrose, HCl, quinine hydrochloride, and NaCl). The networks had four output units representing the basic taste qualities, the values of which provide a measure for similarity of test stimuli (salts, tartaric acid, and umami substances) to the basic taste stimuli. 3. Trained networks discriminated the response patterns to the test stimuli in a plausible manner in light of previous physiological and psychological experiments. Profiles of output values of the networks paralleled those of across-neuron correlations with respect to the highest or second-highest values in the profiles. 4. We evaluated relative contributions of input units to the taste discrimination of the network by examining their significance Sj, which is defined as the sum of the absolute values of the connection weights from the jth input unit to the hidden layer. When the input units with weaker connection weights (e.g., 15 of 39 input units) were "pruned" from the trained network, the ability of the network to discriminate the basic taste qualities as well as other test stimuli was not greatly affected. On the other hand, the taste discrimination of the network progressively deteriorated much more rapidly with pruning of input units with stronger connection weights. 5. These results suggest that cortical taste neurons differentially contribute to the coding of taste qualities. The pruning technique may enable the evaluation of a given taste neuron in terms of its relative contribution to the coding, with Sj providing a quantitative measure for such evaluation.
Cholecystokinin depolarizes rat thalamic reticular neurons by suppressing a K+ conductance
Authors: Cox C. L. , Huguenard J. R. , Prince D. A.
Published: December 2017

1. The thalamic reticular nucleus (nRt) is innervated by cholecystokinin (CCK)-containing neurons and contains CCK binding sites. We used tight-seal, whole cell recording techniques with in vitro rat thalamic slices to investigate the action of CCK on neurons in nRt and ventrobasal thalamus (VB). 2. Brief applications of the CCK agonist cholecystokinin octapeptide (26-33) sulfated (CCK8S) evoked prolonged spike discharges in nRt neurons but had no direct effects on VB neuron activity. This selective excitatory action of CCK8S in nRt resulted from a long-lasting membrane depolarization (2-10 min) associated with an increased input resistance. Voltage-clamp recordings revealed that CCK8S reduced membrane conductance by 0.6-3.8 nS, which amounted to 5-54% of the resting conductance of these neurons. 3. The conductance blocked by CCK8S was linear over the range of -50 to -100 mV and reversed near the potassium equilibrium potential. Modifications of extracellular K+ concentration altered the reversal potential of the conductance as predicted by the Nernst equation. The K+ channel blocker Cs+, applied either intracellularly or combined intra- and extracellularly, blocked the response to CCK8S. 4. The CCK8S-induced depolarization persisted after suppression of synaptic transmission by either tetrodotoxin or a low-Ca2+, high-Mg2+ extracellular solution, indicating that the depolarization was primarily due to activation of postsynaptic CCK receptors and not mediated through the release of other neurotransmitters. 5. The selective CCKA antagonists L364,718 and Cam-1481 attenuated the CCK8S-induced depolarization, whereas the CCKB antagonist L365,260 had little or no effect on the depolarization. 6. Our findings indicate that CCK8S, acting via CCKA-type receptors, reduces a K+ leak current, resulting in a long-lasting membrane depolarization that can presumably modify the firing mode of nRt neurons. Through this effect, CCK actions in nRt may strongly influence thalamocortical function.
Plasticity of the extensor group I pathway controlling the stance to swing transition in the cat
Authors: Whelan P. J. , Hiebert G. W. , Pearson K. G.
Published: December 2017

1. This study examines whether the efficacy of polysynaptic group I excitatory pathways to extensor motoneurons are modified after axotomy of a synergistic nerve. Previously, it has been shown that stimulation of extensor nerves at group I strength can extend the stance phase and delay swing. Stimulation of the lateral gastrocnemius and soleus (LG/S) nerve prolongs stance for the duration of the stimulus train, whereas stimulation of the medial gastrocnemius (MG) nerve moderately increases stance. Our hypothesis was that after axotomy of the LG/S nerve the efficacy of the MG group I input would increase. 2. This idea was tested in 10 adult cats that had their left LG/S nerves axotomized for 3-28 days. On the experimental day the cats were decerebrated and the left (experimental) and right (control) LG/S and MG nerves were stimulated during late stance as the animals were walking on a motorized treadmill. A significant increase in the efficacy of the left MG nerve occurred 5 days after axotomy of the LG/S nerve when compared with the control response. By contrast, the previously cut LG/S nerve showed a reduction in efficacy after 3 days compared with the control limb. 3. Functionally, this plasticity may be an important mechanism by which the strength of the group I pathway is calibrated to different loads on the extensor muscles.
Cerebral serotonergic neurons reciprocally modulate swim and withdrawal neural networks in the mollusk Clione limacina
Authors: Norekian T. P. , Satterlie R. A.
Published: December 2017

1. A pair of serotonin-immunoreactive neurons has been identified in the cerebral ganglia of the pteropod mollusk Clione limacina, which produce coordinated, excitatory/inhibitory effects on neurons controlling two incompatible behaviors, swimming and whole body withdrawal. These cells were designated cerebral serotonergic ventral (Cr-SV) neurons. 2. Activation of Cr-SV neurons produces a prominent inhibition of the pleural withdrawal neurons, which have been previously shown to induce whole body withdrawal in Clione. In addition, the cerebral neurons produce weak excitatory inputs to swim motor neurons, pedal serotonergic neurons involved in the peripheral modulation of swimming, and to the serotonergic heart excitor neuron. 3. Inhibitory and excitatory effects appear to be produced by serotonin because they are mimicked by exogenous serotonin and are blocked by the serotonin antagonist mianserin. 4. All serotonergic neurons identified thus far in the CNS of Clione appear to function in a coordinated manner, altering a variety of neural centers all directed toward the activation of swimming behavior.
Role of the afterhyperpolarization in control of discharge properties of septal cholinergic neurons in vitro
Authors: Gorelova N. , Reiner P. B.
Published: December 2017

1. The properties of the cholinergic neurons of the rat medial septum and nucleus of the diagonal band of Broca (MS/DBB) were studied using whole cell patch-clamp recordings in an in vitro slice preparation. 2. Both the transmitter phenotype and the intrinsic membrane properties of 56 MS/DBB neurons were determined post hoc by visualizing intracellularly deposited biocytin with fluorescent avidin and endogenous choline acetyltransferase with immunofluorescence. Twenty seven of 28 MS/DBB neurons exhibiting both a prominent slow afterhyperpolarization (sAHP) following a single action potential and anomalous rectification were identified as cholinergic. The remaining 28 neurons exhibited other intrinsic membrane properties and none were choline acetyltransferase immunoreactive. 3. The sAHP in MS/DBB cholinergic neurons was blocked reversibly either by reducing extracellular calcium or addition of 100 microM cadmium and irreversibly blocked by 30 nM apamin, suggesting that the sAHP is produced by an apamin-sensitive calcium-activated potassium conductance. 4. MS/DBB cholinergic neurons also exhibited a postspike depolarizing afterpotential (DAP) preceeding the sAHP. Both the DAP and the sAHP were blocked when extracellular calcium was lowered as well as in the presence of 10-50 microM NiCl2. Application of 500 nM omega-conotoxin also reduced the sAHP, while leaving the DAP intact. These data suggest that both transient and high-threshold calcium conductances contribute to generation of the sAHP. 5. When depolarized, cholinergic neurons fired slowly (2-4 Hz) and regularly with little evidence of spike frequency adaptation. When the sAHP was blocked with apamin, the instantaneous frequency of firing increased and the neuron now exhibited prominent spike frequency adaptation. 6. Serotonin (5-HT) reversibly suppressed the sAHP in MS/DBB cholinergic neurons and altered the firing pattern from slow regular discharge to one which exhibited modest spike frequency adaptation. 7. It was concluded that the sAHP limits the firing rate of MS/DBB cholinergic neurons and that physiologically relevant supression of the sAHP by 5-HT may result in state-dependent changes in the discharge pattern of MS/DBB cholinergic neurons.
Electrical properties of neocortical neurons in slices from children with intractable epilepsy
Authors: Tasker J. G. , Hoffman N. W. , Kim Y. I. , Fisher R. S. , Peacock W. J. , Dudek F. E.
Published: December 2017

1. The intrinsic electrical properties of human neocortical neurons were studied with current-clamp and single-electrode voltage-clamp techniques in slices obtained from children, aged 3 mo to 15 yr, undergoing surgical treatment of intractable epilepsy. Neocortical samples were classified as most or least abnormal based on clinical data. Recorded neurons were labeled with biocytin for correlation of electrical properties with morphological characteristics and laminar position. All recorded neurons were divided into three cell types--fast-spiking, low-threshold spiking (LTS) and non-LTS cells--on the basis of their electrical characteristics. 2. Fast-spiking cells generated brief, rapidly repolarizing action potentials. Most of these cells showed only weak spike-frequency adaptation. Fast-spiking cells labeled with biocytin were aspiny or sparsely spiny nonpyramidal neurons located in cortical layers 2-4. 3. LTS cells generated Ca(2+)-dependent low-threshold potentials and were the most numerous of the three cell types. Their Na(+)-dependent action potentials were broader than those of fast-spiking cells and showed marked spike-frequency adaptation. The size of low-threshold Ca2+ potentials and currents varied across cells, but they never supported more than two or, occasionally, three fast action potentials. LTS cells were pyramidal neurons located throughout cortical layers 2-6. Unlike the bursting neocortical cells described in lower mammals, LTS neurons in neocortex from children failed to generate bursts of inactivating Na+ action potentials. 4. Non-LTS cells also had relatively broad Na(+)-dependent action potentials and showed spike-frequency adaptation, but they did not generate detectable low-threshold potentials or currents. Non-LTS cells were also pyramidal neurons located throughout layers 2-6. 5. The electrical properties of cells from different age groups (< or = 1, 2-8, and 9-15 yr) and from most-abnormal and least-abnormal tissue samples were compared. A statistically significant trend toward a lower input resistance, a faster membrane time constant, and a decreased spike duration was observed with increasing age. There were no significant differences between the electrical properties of cells from the most-abnormal tissue and cells from the least-abnormal tissue. 6. These data indicate that the intrinsic electrical properties of neocortical neurons from children vary according to cell morphology and change with increasing age, as has been observed in rodent and feline neocortical neurons. No obvious evidence of epileptogenicity was detected in the intrinsic electrical properties of any of the neurons studied.
Presynaptic inhibition of sensory neurons during kicking movements in the locust
Authors: Hedwig B. , Burrows M.
Published: December 2017

1. Locusts use a distinctive motor pattern to extend the tibia of a hind leg rapidly in a defensive kick, or to extend the tibiae of both hind legs in a jump. The force for the movement is generated by an almost isometric co-contraction of the extensor and flexor tibiae muscles followed by a sudden release of the stored energy when the flexor motor neurons are inhibited. A proprioceptor (the femoral chordotonal organ) spans the femorotibial joint, and at least 50 of its sensory neurons each signal particular features of its movements. Intracellular recordings from these neurons close to their terminals in the CNS show that their spikes during kicking are superimposed on a depolarizing synaptic input generated near their output terminals. The depolarization is linked to the time in the motor pattern when the sensory neurons spike. 2. Flexion-sensitive neurons spike and their terminals are depolarized when the tibia is initially flexed and when the tibia rebounds from the rapid extension of the kick. Some respond phasically, others more tonically and over different ranges of joint angles, but all receive a depolarizing synaptic input when they spike. The depolarization of the terminals precedes the spikes and often occurs concurrently with the changes in the membrane potentials of the motor neurons. The input persists while the tibia is held fully flexed before the kick. 3. Extension-sensitive neurons spike and their terminals are depolarized when the tibia is rapidly extended and this depolarization may outlast the spikes at the completion of a kick. Some of these depolarizing synaptic potentials occur before the movement starts, which suggests that they may result from central elements of the motor pattern; others however are clearly consequent upon joint movements. During the co-contraction that precedes the movement, these neurons do not spike and their membrane potential repolarizes because of a reduction in the synaptic input. 4. The depolarizing synaptic potentials are associated with a fall in the resistance of the membrane and may be attributed to the same gamma-aminobutyric acid-mediated mechanism already identified at the terminals of these sensory neurons. The effect and timing of the depolarization of the terminals during this voluntary movement should be to reduce the effectiveness of the sensory neurons in transmitting signals to their postsynaptic neurons in the CNS. This could therefore be part of a mechanism that allows voluntary movements to proceed in the presence of self-generated sensory feedback which might otherwise impede that movement.
Hunger and satiety modify the responses of olfactory and visual neurons in the primate orbitofrontal cortex
Authors: Critchley H. D. , Rolls E. T.
Published: December 2017

1. The primate orbitofrontal cortex is the site of convergence of information from primary taste and primary olfactory cortical regions. In addition, it receives projections from temporal lobe visual areas concerned with the representation of objects such as foods. Previous work has shown that the responses of gustatory neurons in the secondary taste area within the orbitofrontal cortex are modulated by hunger and satiety, in that they stop responding to the taste of a food on which an animal has been fed to behavioral satiation, yet may continue to respond to the taste of other foods. 2. This study demonstrates a similar modulation of the responses of olfactory and visual orbitofrontal cortex neurons after feeding to satiety. Seven of nine olfactory neurons that were responsive to the odors of foods, such as blackcurrant juice, were found to decrease their responses to the odor of the satiating food in a selective and statistically significant manner. 3. It also was found for eight of nine neurons that had selective responses to the sight of food, that they demonstrated a sensory-specific reduction in their visual responses to foods after satiation. 4. The responses of orbitofrontal cortex neurons selective for foods in more than one modality also were analyzed before and after feeding to satiation. Satiety often affected the responses of these multimodal neurons across all modalities, but a sensory-specific effect was not always demonstrable for both modalities. 5. These findings show that the olfactory and visual representations of food, as well as the taste representation of food, in the primate orbitofrontal cortex are modulated by hunger. Usually a component related to sensory-specific satiety can be demonstrated. The findings link at least part of the processing of olfactory and visual information in this brain region to the control of feeding-related behavior.
Relation of chemical structure to spatial distribution of sensory responses in rat olfactory epithelium
Authors: Scott J. W. , Davis L. M. , Shannon D. , Kaplan C.
Published: December 2017

1. Electroolfactogram (EOG) recordings were made in three configurations from the rat olfactory epithelium. Each configuration compared recordings in the dorsomedial recess of the epithelium with recordings in ventral or lateral parts of the epithelium. Most comparisons were made with simultaneous recordings. The exception was a series in which the dorsal recess and lateral space between the base of two turbinate bones were directly exposed for odor application and recording. The spatial distributions of maximal responses were largely independent of recording configuration. 2. Simultaneous recordings compared dorsomedial and lateral sites in the epithelium during stimulation with a series of 50 odorants. The odorants that evoked larger responses in the lateral sites were usually compounds that lacked oxygen containing functional groups (such as the carbonyl group). This was true for straight chain and cyclic alkanes, for terpine compounds, and for aromatic compounds. The major exception was cineole, a bicyclic compound. All compounds containing ketone groups evoked larger dorsomedial responses. The responses of aldehydes and esters depended upon whether they were attached to aliphatic or aromatic chains. 3. In the three types of preparation, the sites responding best to ketones were in the same expression zone of the epithelium according to published maps for the rat and mouse. The sites responding best to odors without functional groups were in the far lateral or ventral region and corresponded to one of the two most lateral and ventral expression zones. This fact suggests that the receptors in these regions have a preference for particular chemical properties. This level of analysis cannot determine whether all receptors in each zone have a stronger response to certain properties of these odorants or whether each zone contains different proportions of receptors with these properties.