bluuebunny/crossref_metadata_2025_split huggingface dataset:
Co‐operation between neural and myogenic mechanisms in the control of distension‐induced peristalsis in the mouse small intestine
Authors: Huizinga Jan D. , Ambrous Krista , Der‐Silaphet Tara 
Published: September 2004

Myogenic and neural control of intestinal transit were investigated in a model of distension‐induced peristalsis. A comparison was made between the electrical and mechanical activities and outflow of contents observed in control mice and in W/W v mice, which lack the interstitial cells of Cajal associated with Auerbach's plexus.
Distension caused a periodic appearance of increased motor activity due to stimulation of enteric nerves in both control and W/W v mice. Excitation was primarily delivered by cholinergic nerves, whereas periodic inhibition was mediated by neuronal nitric oxide.
In control mice, outflow was driven by propagating slow‐wave activity and was only in the aboral direction. Outflow only occurred when slow waves carried sufficient action potentials to cause phasic intraluminal pressure increases of ≥ 1 cmH2O through direct stimulation of the musculature or by distension‐induced neurally mediated activation.
In W/W v mice, outflow was associated with propagating action potentials that occurred due to either neural stimulation or direct muscle stimulation. Action potential propagation and outflow occurred in both oral and aboral directions.
In summary, in both control and W/W v mice, distension induced periodic motor activity through stimulation of the enteric nervous system. Intraluminal contents were not moved in front of such motor activity. Rather, within such periods of activity that occurred concurrently throughout an entire segment, pulsatile outflow was directed by individual propagating slow waves with superimposed action potentials in control tissue, and by propagating action potentials in W/W v mice, which lack interstitial cells of Cajal.
Submillisecond kinetics and low efficacy of parallel fibre‐Golgi cell synaptic currents in the rat cerebellum
Authors: Dieudonné Stéphane 
Published: September 2004

The whole‐cell configuration of the patch clamp technique was used to record from Golgi cells in thin slices of the rat cerebellum (P12‐P25). Their active membrane properties and the input that they receive from the parallel fibres were characterized.
Most cells were filled with biocytin and morphologically identified by the presence of a large axonal arbor restricted to the granular layer. The morphological parameters of eighteen of the best‐preserved cells were quantified.
A slow capacitive current transient, characteristic of the Golgi cell axon, was used to identify Golgi cells whenever their morphology could not be preserved.
Golgi cells fire action potentials spontaneously at 3 ± 1.7 Hz (n= 17). Their firing frequency increases linearly with the amplitude of depolarizing current pulses and displays marked adaptation.
When hyperpolarized Golgi cells display an anomalous rectification which is blocked by 2 mM CsCl, indicating the presence of an Ih‐like current.
Golgi cells receive a spontaneous excitatory input from parallel fibres. This input is composed of small amplitude, mostly monoquantal, EPSCs. Chemical stimulation of granule cells by locally applied kainate evokes tetrodotoxin (TTX)‐dependent events with similar properties.
The parallel fibre‐Golgi cell EPSCs have both AMPA and NMDA components. The NMDA component is blocked by 1 mM external magnesium at ‐60 mV and decays with time constants of 31 ± 9 ms and 170 ± 15 ms (at +61 mV in the presence of magnesium).
In the presence of 10 μM internal spermine, the AMPA component of the spontaneous EPSCs is markedly slowed (0.96 ± 0.25 ms to 1.86 ± 0.47 ms; n= 4) and reduced in amplitude (49 ± 7 %; n= 4) when depolarizing the cell from ‐70 mV to +61 mV.
The decay kinetics of individual AMPA EPSCs were found to be variable, in part because of dendritic filtering. A more detailed analysis reveals that the synaptic AMPA conductances are regulated during development and close faster at days P19‐P25 than at days P13‐P16.
These data suggest that the efficacy of the parallel fibre‐Golgi cell input is rather low. This places strong constraints on the conditions in which the inhibitory feedback exerted by the Golgi cell can be operational.
The possibility is considered that the Golgi cell‐granule cell circuit shows an oscillatory behaviour. This hypothesis is discussed in relation to the models of Albus and Marr.
Multiple ionic mechanisms mediate inhibition of rat motoneurones by inhalation anaesthetics
Authors: Sirois Jay E. , Pancrazio Joseph J. , Lynch Carl , Bayliss Douglas A. 
Published: September 2004

We studied the effects of inhalation anaesthetics on the membrane properties of hypoglossal motoneurones in a neonatal rat brainstem slice preparation.
In current clamp, halothane caused a membrane hyperpolarization that was invariably associated with decreased input resistance; in voltage clamp, halothane induced an outward current and increased input conductance. Qualitatively similar results were obtained with isoflurane and sevoflurane.
The halothane current reversed near the predicted K+ equilibrium potential (EK) and was reduced in elevated extracellular K+ and in the presence of Ba2+ (2 mm). Moreover, the Ba2+‐sensitive component of halothane current was linear and reversed near EK. The halothane current was not sensitive to glibenclamide or thyrotropin‐releasing hormone (TRH). Therefore, the halothane current was mediated, in part, by activation of a Ba2+‐sensitive K+ current distinct from the ATP‐ and neurotransmitter‐sensitive K+ currents in hypoglossal motoneurones.
Halothane also inhibited Ih, a hyperpolarization‐activated cationic current; this was primarily due to a decrease in the absolute amount of current, although halothane also caused a small, but statistically significant, shift in the voltage dependence of Ih activation. Extracellular Cs+ (3 mm) blocked Ih and a component of halothane‐sensitive current with properties reminiscent of Ih.
A small component of halothane current, resistant to Ba2+ and Cs+, was observed in TTX‐containing solutions at potentials depolarized to ∼−70 mV. Partial Na+ substitution by N‐methyl‐D‐glucamine completely abolished this residual current, indicating that halothane also inhibited a TTX‐resistant Na+ current active near rest potentials.
Thus, halothane activates a Ba2+‐sensitive, relatively voltage‐independent K+ current and inhibits both Ih and a TTX‐insensitive persistent Na+ current in hypoglossal motoneurones. These effects of halothane decrease motoneuronal excitability and may contribute to the immobilization that accompanies inhalation anaesthesia.
Modulation of the unitary exocytic event amplitude by cAMP in rat melanotrophs
Authors: Sikdar Sujit K. , Kreft Marko , Zorec Robert 
Published: September 2004

Secretory responses were measured in single rat pituitary melanotrophs as the relative increase in membrane capacitance (Cm) 8 min after the start of dialysis with solutions containing 0.45 μm Ca2+. In the added presence of cAMP (0.2 mM) in the patch pipette solution, capacitance responses increased 2‐ to 3‐fold in comparison with controls.
To study whether cAMP‐dependent mechanisms affect cytosolic calcium activity ([Ca2+]i), dibutyryl cyclic AMP (dbcAMP, 10 mM) was added to intact melanotrophs and [Ca2+]i was measured using fura‐2 AM. Addition of dbcAMP caused a transient reduction in [Ca2+]i to 82 ± 21 nM from a resting value of 100 ± 19 nM (mean ± s.e.m., n= 32, P < 0.002), indicating that the cAMP‐induced increase in secretory activity was not the result of cAMP acting to increase [Ca2+]i, which then increased secretory activity.
To investigate whether cAMP affects the secretory apparatus directly, the interaction of a single secretory granule with the plasmalemma was monitored by measuring discrete femtofarad steps in Cm. The signal‐to‐noise ratio of recordings was increased by pre‐incubating the cells with a hydrophobic anion, dipicrylamine.
Recordings of unitary exocytic events (discrete ‘on’ steps in Cm) showed that the amplitude of ‘on’ steps ‐ a parameter correlated to the size of exocytosing secretory granules ‐ increased from 4.2 ± 0.2 fF (n= 356) in controls to 7.9 ± 0.2 fF in the presence of cAMP (n= 329, P < 0.001), while the frequency of unitary exocytic events was similar in controls and in the presence of cAMP.
The results suggest that a cAMP‐dependent mechanism mediates the fusion of larger granules with the plasmalemma.
The role of GABAergic inputs for coincidence detection in the neurones of nucleus laminaris of the chick
Authors: Funabiki Kazuo , Koyano Konomi , Ohmori Harunori 
Published: September 2004

Synaptic inputs to nucleus laminaris (NL) neurones were studied in a brainstem slice preparation of chick embryos (E15‐20) using the whole‐cell patch clamp technique. NL neurones are third order auditory neurones and are proposed to behave as coincidence detectors concerned with interaural timing discrimination.
Under voltage clamp conditions, electrical stimuli applied to either ventral or dorsal dendritic layers evoked EPSCs. These fast currents decayed with a time constant of 1.1 ms near the resting potential, reversed close to 0 mV, and were blocked by 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX, 20 μM) or 6,7‐dinitro‐quinoxaline‐2,3‐dione (DNQX, 20 μM). Coincident or near coincident stimulation of the ventral and the dorsal dendritic layers increased the probability of action potential generation (response probability).
In the presence of CNQX (40 μM) other postsynaptic currents (PSCs) were observed, which reversed close to the equilibrium potential for chloride (ECl), and were reversibly blocked by bicuculline (20 μM) and, therefore, were mediated by GABAA receptors. Spontaneous GABAergic PSCs were inward going near the resting membrane potential immediately after starting whole‐cell recording with a low Cl− (5 mM, ECl= ‐90 mV) pipette medium, but became outward‐going with time. This indicates that GABAergic inputs may generate depolarizing potentials in intact NL neurones.
Local GABA (10 μM) application reduced both the EPSP and EPSC amplitude and shortened the EPSP decay time constant (from 5.3 to 2.1 ms), while the EPSC decay time constant was not affected (from 1.3 to 1.2 ms). These GABA effects were mostly due to the shunting conductance of the postsynaptic GABAA receptors.
Depolarizing current injections combined with electrical stimuli to a unilateral axon bundle simulated bilateral synaptic inputs. Response probability increased with decreased interstimulus intervals, while local GABA (10 μM) application to the soma narrowed the time dependence of the response probability.
These results suggest that GABAergic inputs to NL neurones may serve to improve coincidence detection of the bilateral excitatory inputs through an increase in membrane conductance.
Association of somatic action potential shape with sensory receptive properties in guinea‐pig dorsal root ganglion neurones
Authors: Djouhri L. , Bleazard L. , Lawson S. N. 
Published: September 2004

Intracellular voltage recordings were made from the somata of L6 and S1 dorsal root ganglion (DRG) neurones at 28.5–31 °C in young guinea‐pigs (150–300 g) anaesthetized with sodium pentobarbitone. Action potentials (APs) evoked by dorsal root stimulation were used to classify conduction velocities (CVs) as C, Aδ or Aα/β. Units with overshooting APs and membrane potentials (Vm) more negative than −40 mV were analysed: 40 C‐, 45 Aδ‐ and 94 Aα/β‐fibre units.
Sensory receptive properties were characterized as: (a) low‐threshold mechanoreceptive (LTM) units (5 C‐, 10 Aδ‐ and 57 Aα/β‐fibre units); (b) nociceptive units, responding to noxious mechanical stimuli, some also to noxious heat (40 C‐, 27 Aδ‐ and 27 Aα/β‐fibre units); (c) unresponsive units that failed to respond to a variety of tests; and (d) C‐fibre cooling‐sensitive units (n= 4). LTM units made up about 8 % of identified C‐fibre units, 36 % of identified Aδ‐fibre units and > 73 % of identified Aα/β‐fibre units. Compared with LTM units, the nociceptive units had APs that were longer on average by 3 times (C‐fibre units), 1.7 times (Aδ‐fibre units) and 1.4 times (Aα/β‐fibre units). They also had significantly longer rise times (RTs) and fall times (FTs) in all CV ranges. Between Aα/β‐nociceptors and Aα/β‐LTMs there was a proportionately greater difference in RT than in FT. The duration of the afterhyperpolarization measured to 80 % recovery (AHP80) was also significantly longer in nociceptive than LTM neurones in all CV ranges: by 3 times (C‐fibre units), 6.3 times (Aδ‐fibre units) and 3.6 times (Aα/β‐fibre units). The mean values of these variables in unresponsive units were similar to those of nociceptive units in each CV range; in C‐ and Aδ‐fibre groups their mean AHP duration was even longer than in nociceptive units.
A‐fibre LTM neurones were divided into Aδ‐ (D hair units, n= 8), and Aα/β‐ (G hair/field units, n= 22; T (tylotrich) hair units, n= 6; rapidly adapting (RA) glabrous units, n= 6; slowly adapting (SA) hairy and glabrous units, n= 2; and muscle spindle (MS) units n= 17). MS and SA units had the shortest duration APs, FTs and AHP80s of all these groups. The mean RT in D hair units was significantly longer than in all Aα/β LTM units combined. T hair units had the longest mean FT and AHP of all the A‐LTM groups. The mean AHP was about 10 times longer in T hair units than in all other A‐LTM units combined (significant), and was similar to that of A‐fibre nociceptive neurones.
These differences in somatic AP shape may aid in distinguishing between LTM and nociceptive or unresponsive C‐ and Aδ‐fibre units but probably not between nociceptive and unresponsive units. The differences seen may reflect differences in expression or activation of different types of ion channel.
Sensorimotor modulation of human cortical swallowing pathways
Authors: Hamdy Shaheen , Aziz Qasim , Rothwell John C. , Hobson Anthony , Thompson David G. 
Published: September 2004

Transcranial magnetic stimulation over motor areas of cerebral cortex in man can activate short latency bilateral cortical projections to the pharynx and oesophagus. In the present paper we investigate the interaction between pathways from each hemisphere and explore how activity in these pathways is modulated by afferent feedback from the face, pharynx and oesophagus.
Comparison of unilateral and bilateral stimulation (using interstimulus intervals (ISIs) of 1, 5 or 10 ms between shocks) showed spatial summation of responses from each hemisphere at an ISI of 1 ms, indicating that cortical efferents project onto a shared population of target neurones. Such summation was not evident at ISIs of 5 or 10 ms. There was little evidence for transcallosal inhibition of responses from each hemisphere, as described for limb muscles.
Single stimuli applied to the vagus nerve in the neck or the supraorbital nerve, which alone produce intermediate (onset 20‐30 ms) and long (50‐70 ms) latency reflex responses in the pharynx and oesophagus, were used to condition the cortical responses. Compared with rest, responses evoked by cortical stimulation were facilitated when they were timed to coincide with the late part of the reflex. The onset latency was reduced during both parts of the reflex response. No facilitation was observed with subthreshold reflex stimuli.
Single electrical stimuli applied to the pharynx or oesophagus had no effect on the response to cortical stimulation. However, trains of stimuli at frequencies varying from 0.2 to 10 Hz decreased the latency of the cortically evoked responses without consistently influencing their amplitudes. The effect was site specific: pharyngeal stimulation shortened both pharyngeal and oesophageal response latencies, whereas oesophageal stimulation shortened only the oesophageal response latencies.
Cortical swallowing motor pathways from each hemisphere interact and their excitability is modulated in a site‐specific manner by sensory input. The latter may produce a mixture of excitation and inhibition at both brainstem and cortical levels.
Postnatal changes in responses of rat dorsal horn cells to afferent stimulation: a fibre‐induced sensitization
Authors: Jennings Ernest , Fitzgerald Maria 
Published: September 2004

In vivo extracellular recordings were made of 171 dorsal horn cells in both superficial and deep laminae in urethane‐anaesthetized newborn rats aged 3, 6, 10 and 21 days, and their response to single and repeated stimuli to primary afferent fibres investigated.
No long‐latency spike responses were evoked in response to C fibre stimulation in pups at postnatal day 3 (P3) or P6, while by P10, 35 % of cells had a C fibre response. Latencies of response to A fibre skin stimulation were very long and varied widely in the youngest animals, particularly in superficial cells, but mean latencies decreased with postnatal age, from 33.1 ± 2.78 ms at P3 to 7.3 ± 0.3 ms at P21. The mean number of spikes evoked by a single A fibre skin stimulus was remarkably consistent between cells and not significantly different in superficial and deep laminae at each age. The mean value of 5.1 ± 0.6 at P3 increased to 7.0 ± 1.4 at P10.
Repeated stimulation of cutaneous A fibres at 0.5 Hz at twice the threshold level did not significantly alter the magnitude of the evoked response but led to shifts in latency, or ‘latency jitter’, which decreased with age. Deeper cells displayed more latency jitter than superficial cells.
Repeated stimulation of cutaneous A fibres at 0.5 Hz at twice the threshold level produced considerable sensitization in a population of dorsal horn cells in the neonate. This sensitization was unlike the classic C fibre‐evoked ‘wind‐up’ observed in adult dorsal horn. The direct A fibre‐evoked activity did not increase, but the background activity increased during repetitive stimulation leading to a prolonged after‐discharge beyond the stimulation period. At P6, 33 % of cells were sensitized, displaying a mean after‐discharge of 70.6 ± 18 s. At P10, only 6 % were sensitized, with a mean after‐discharge of 63 s, and by P21, sensitization was no longer observed.
The present study demonstrates that the postsynaptic activity evoked in neonatal dorsal horn cells by cutaneous afferents differs considerably from that in adults. The results may account for the known behavioural reflex sensitization to low‐intensity cutaneous stimulation observed in neonatal rats and man.
Medullary raphe neurones and baroreceptor modulation of the respiratory motor pattern in the cat
Authors: Lindsey B. G. , Arata A. , Morris K. F. , Hernandez Y. M. , Shannon R. 
Published: September 2004

Perturbations of arterial blood pressure change medullary raphe neurone activity and the respiratory motor pattern. This study sought evidence for actions of baroresponsive raphe neurones on the medullary respiratory network.
Blood pressure was perturbed by intravenous injection of an α1‐adrenergic receptor agonist, unilateral pressure changes in the carotid sinus, or occlusion of the descending aorta in thirty‐six Dial‐urethane‐anaesthetized, vagotomized, paralysed, artificially ventilated cats. Neurones were monitored with microelectrode arrays in two or three of the following domains: nucleus raphe obscurus‐nucleus raphe pallidus, nucleus raphe magnus, and rostral and caudal ventrolateral medulla. Data were analysed with cycle‐triggered histograms, peristimulus time and cumulative sum histograms, cross‐correlograms and spike‐triggered averages of efferent phrenic nerve activity.
Prolongation of the expiratory phase and decreased peak integrated phrenic amplitude were most frequently observed. Of 707 neurones studied, 310 had altered firing rates during stimulation; changes in opposite directions were monitored simultaneously in fifty‐six of eighty‐seven data sets with at least two baroresponsive neurones.
Short time scale correlations were detected between neurones in 347 of 3388 pairs. Seventeen pairs of baroresponsive raphe neurones exhibited significant offset correlogram features indicative of paucisynaptic interactions. In correlated raphe‐ventrolateral medullary neurone pairs with at least one baroresponsive neurone, six of seven ventrolateral medullary decrementing expiratory (E‐Decr) neurones increased their firing rate during baroreceptor stimulation. Thirteen of fifteen ventrolateral medullary inspiratory neurones correlated with raphe cells decreased their firing rate during baroreceptor stimulation.
The results support the hypothesis that raphe neuronal assemblies transform and transmit information from baroreceptors to neurones in the ventral respiratory group. The inferred actions both limit and promote responses to sensory perturbations and match predictions from simulations of the respiratory network.
A slow calcium‐dependent component of charge movement in Rana temporaria cut twitch fibres
Authors: Hui Chiu Shuen 
Published: September 2004

Charge movement was studied in highly stretched frog cut twitch fibres in a double Vaseline‐gap voltage‐clamp chamber, with the internal solution containing either 0.1 mM EGTA or 20 mM EGTA plus 1.8 mM total Ca2+.
Fibres were stimulated with TEST pulses lasting 100‐400 ms. Replacement of the external Cl− with an ‘impermeant’ anion, such as SO42‐, CH3SO3−, gluconate or glutamate, greatly reduced the calcium‐dependent Cl− current in the ON segment and generated a slowly decaying inward OFF current in charge movement traces.
Application of 20 mM EGTA to the internal solution abolished the slow inward OFF current, implying that the activation of the current depended on the presence of Ca2+ in the myoplasm. The possibility that the slow inward OFF current was carried by cations flowing inwards or anions flowing outwards was studied and determined to be unlikely.
During a long (2000 ms) TEST pulse, a slowly decaying ON current was also observed. When the slow ON and OFF currents were included as parts of the total charge movement, ON‐OFF charge equality was preserved. This slow capacitive current is named Iδ.
When Cl− was the major anion in the external solution, the OFF Iδ was mostly cancelled by a slow outward current carried by the inflow of Cl−.
The OFF Iδ component showed a rising phase. The average values of the rising time constants in CH3SO3− and SO42‐ were similar and about half of that in gluconate.
The OFF Iδ component in CH3SO3− had a larger magnitude and longer time course than that in SO42‐. The maximum amount of Qδ in CH3SO3− was about three times as much as that in SO42‐, whereas the voltage dependence of Qδ was similar in the two solutions.
Since the existence of Qδ depends on the presence of Ca2+ in the myoplasm, it is speculated that Qδ could be a function of intracellular calcium release.