bluuebunny/crossref_metadata_2025 huggingface dataset:
Substance P mediates neurogenic vasodilatation in extrinsically denervated guinea‐pig submucosal arterioles.
Authors: Galligan J J , Jiang M M , Shen K Z , Surprenant A
Published: December 2014

1. Arteriolar diameter was measured using an optical method in preparations of guinea‐pig submucosal plexus in vitro. Electrical stimulation of one or more neurones in ganglia of the submucosal plexus causes a cholinergic vasodilatation in normal animals. The vasomotor innervation to the arterioles was studied in guinea‐pigs in which the extrinsic nerves to the intestine had been removed. Tissues were processed for immunohistochemistry after the in vitro experiments. 2. Extrinsic denervation resulted in complete loss of catecholamine fluorescence, NPY (neuropeptide Y) and CGRP (calcitonin gene‐related peptide) immunofluorescence around the blood vessels and no neurogenic vasoconstriction was observed up to 60 days post‐denervation. Vasodilatation in response to ganglionic stimulation was increased; smaller arterioles (outside diameter less than 40 microns) showed a greater enhancement of neurogenic vasodilatation than larger arterioles. 3. Nerve‐evoked vasodilatations were only partially inhibited by muscarinic antagonists at 30‐60 days after extrinsic denervations. 4. The non‐cholinergic neurogenic vasodilatation was abolished by the substance P antagonists, spantide, [D‐Arg1, D‐Pro2, D‐Trp7.9, Leu11]substance P and [D‐Arg1, D‐Phe5, D‐Trp7.9, Leu11]substance P. These antagonists did not alter the cholinergic vasodilatation in normal or extrinsically denervated arterioles. 5. Exogenous substance P dilated all submucosal arterioles; the concentration which produced half‐maximal vasodilatations was 2.5 mM in both normal and extrinsically denervated arterioles. Substance P antagonists inhibited the vasodilatation caused by substance P at concentrations similar to those needed to block nerve‐mediated vasodilatation. 6. There was a strong correlation between the finding of non‐cholinergic vasodilatation in response to ganglionic stimulation, and the presence of substance P‐immunoreactive fibres running from ganglion to arteriole. This correlation did not exist for VIP (vasoactive intestinal peptide). 7. These results suggest that intrinsic intestinal substance P‐containing nerve fibres supply submucosal arterioles after sympathetic efferents and sensory afferents are removed. Stimulation of these nerves releases substance P to produce arteriolar dilatation.
Cardiovascular and ventilatory responses to dynamic exercise during epidural anaesthesia in man.
Authors: Fernandes A , Galbo H , Kjaer M , Mitchell J H , Secher N H , Thomas S N
Published: December 2014

1. In order to evaluate the importance of afferent neural feedback from the working muscles for cardiovascular and ventilatory responses to dynamic exercise, epidural anaesthesia was induced at L3‐L4. Six healthy males cycled for 20 min at 57% of maximum oxygen uptake and for 8‐12 min at increasing work intensities until exhaustion at 238 +/‐ 30 W without as well as with epidural anaesthesia. 2. Presence of afferent neural blockade was verified by cutaneous sensory analgesia below T10‐T11 and attenuated post‐exercise ischaemic pressor response (45 +/‐ 8‐24 +/‐ 6 mmHg). Efferent sympathetic nerves appear to be intact since basal heart rate and blood pressure as well as the cardiovascular responses to a Valsalva manoeuvre and to a cold pressor test were unchanged. 3. During dynamic exercise with epidural anaesthesia, blood pressure was lower than in control experiments; however, ventilation and heart rate were not affected. 4. The results indicate that afferent neural activity from the working muscles is important for blood pressure regulation during dynamic exercise in man but may not be necessary for eliciting the ventilatory and heart rate responses.
Intracellular chloride activity in glial cells of the leech central nervous system.
Authors: Ballanyi K , Schlue W R
Published: December 2014

1. Chloride‐sensitive double‐barrelled microelectrodes were used to measure the intracellular Cl‐ activity (aicl) and membrane potential (Em) in neuropile glial cells of the leech, Hirudo medicinalis. 2. A close relation between the equilibrium potential for Cl‐ (ECl = ‐66.1 +/‐ 4.9 mV; mean +/‐ S.D.) and the resting potential (Em = ‐67.8 +/‐ 5.2 mV; n = 19) was observed in nominally CO2‐HCO3(‐)‐free, HEPES‐buffered solutions. A saline buffered with 2% CO2, 11 mM‐HCO3‐ elicited a membrane hyperpolarization and a concomitant decrease of aCl. 3. Changes in ECl followed these of Em with a lag of less than 30 s in response to various extracellular K+ concentrations [( K+]o) or due to bath‐application of carbachol or serotonin. 4. Introduction of a Cl(‐)‐free solution resulted in a transient depolarization indicating a substantial Cl‐ conductance and a rapid decrease of aiCl to an apparent value of 0.5‐0.9 mM. 5. The loop diuretics furosemide (1 mM) and bumetanide (0.2 mM) did not affect the K(+)‐induced changes of aiCl. 6. The results indicate a passive Cl‐ distribution across the membrane of leech neuropile glial cells as a result of a high Cl‐ conductance.
Physiological properties of skinned fibres from normal and dystrophic (Duchenne) human muscle activated by Ca2+ and Sr2+.
Authors: Fink R H , Stephenson D G , Williams D A
Published: December 2014

1. Contractile activation properties of various types of normal and dystrophic (Duchenne muscular dystrophy, DMD) human muscle fibres were investigated using mechanically skinned fibres activated in Ca2(+)‐ and Sr2(+)‐buffered solutions at room temperature (21‐25 degrees C). 2. The majority of the normal human muscle fibres (18/22; 82%) could be classified according to the Ca2(+)‐ and Sr2(+)‐activation characteristics in the same three major groups as other mammalian skeletal muscle fibres studied previously: slow‐twitch (8/22; 36%), fast‐twitch (3/22; 14%) and fast‐twitch intermediate (7/22; 32%), which correspond to the three major histological fibre types I, II B and IIA respectively. 3. Of these three major groups only the slow‐twitch (type I; 14/24; 58%) and the fast‐twitch intermediate (type IIA; 3/24; 13%) fibres were found in the DMD muscle, indicating that fast‐twitch fibres of type IIB were in very low proportion in DMD muscle. 4. The DMD muscle contained a new group of fibres (4/24; 17%) with different Ca2(+)‐ and Sr2(+)‐activation characteristics from the three major histological types. This group of fibres is likely to be of embryonic type. 5. The maximum tension development ability of DMD fibres was less than 20% of that in normal fibres with the exception of some slow‐twitch fibres which could produce near normal tension. 6. A significant proportion of normal (4/22; 18%) and DMD (3/24; 13%) fibres were found to have a mixture of Ca2(+)‐ and Sr2(+)‐activation characteristics. This can be explained by co‐existence of various myofibrillar protein isoforms in different proportions with regulatory functions in the same individual fibre. 7. The results demonstrate that DMD leads to marked diminution in the ability of most individual skeletal muscle fibres to develop tension, and causes changes in the overall fibre‐type distribution in afflicted muscles.
A K+ channel in Xenopus nerve fibres selectively blocked by bee and snake toxins: binding and voltage‐clamp experiments.
Authors: Bräu M E , Dreyer F , Jonas P , Repp H , Vogel W
Published: December 2014

1. The effects of mast cell degranulating peptide (MCDP), a toxin from the honey bee, and of dendrotoxin (DTX), a toxin from the green mamba snake, were studied in voltage‐clamp experiments with myelinated nerve fibres of Xenopus. 2. MCDP and DTX blocked part of the K+ current. About 20% of the K+ current, however, was resistant to the toxins even in high concentrations. In Ringer solution half‐maximal block was reached with concentrations of 33 nM‐MCDP and 11 nM‐DTX. In high‐K+ solution the potency of both toxins was lower. beta‐Bungarotoxin (beta‐BuTX), another snake toxin, also blocked part of the K+ current, but was less potent than MCDP and DTX. 3. Tail currents in high‐K+ solution were analysed and three K+ current components were separated according to Dubois (1981 b). Both MCDP and DTX selectively blocked a fast deactivating, slowly inactivating K+ current component which steeply activates between E = ‐60 mV and E = ‐40 mV (component f1). In concentrations around 100 nM, MCDP and DTX blocked neither the slow K+ current (component s) nor the fast deactivating, rapidly inactivating K+ current which activates between E = ‐40 mV and E = 20 mV (component f2). Similar results could be derived from K+ outward currents in Ringer solution. In high‐K+, IC50 of MCDP for component f1 was 99 nM, whereas it was 7.6 microM for f2. Corresponding values for DTX are 68 nM and 1.8 microM. 4. Binding studies with nerve fibre membranes of Xenopus reveal high‐affinity binding sites for 125I‐labelled DTX (KD = 22 pM in Ringer solution and 81 pM in high‐K+ solution). 125I‐labelled DTX can be displaced from its sites completely by unlabelled DTX, toxin I (black mamba toxin), MCDP, and partially by beta‐BuTX. 5. Immunocytochemical staining demonstrates that binding sites for DTX are present in nodal and paranodal regions of the axonal membrane. 6. The axonal membrane of motor and sensory nerve fibres is equipped with three types of well‐characterized K+ channels and constitutes so far the best preparation to study MCDP‐ and DTX‐sensitive K+ channels with electrophysiological and biochemical methods.
Spatial patterns of reflex evoked by pressure stimulation of the foot pads in cats.
Authors: Hongo T , Kudo N , Oguni E , Yoshida K
Published: December 2014

1. The spatial patterns of reflexes elicited by localized pressure stimulation of the foot skin were analysed by recording electromyographic activities of various hindlimb muscles or muscle nerve discharges in cats anaesthetized with sodium pentobarbitone. 2. Reflex discharges evoked by stimulation of the central pad occurred mainly in physiological toe extensors located in the foot. Stimulus‐response relationships of single motor units revealed characteristically wide ranges of graded response and recruitment. 3. Within the central pad, the strongest excitation was evoked from the central lobe and was distributed to extensors of all four toes. Excitation from the medial and the lateral lobes was usually asymmetrical and weaker in toe muscles of the stimulated side. It is suggested that the weakness was in part due to concomitant inhibition. 4. Stimulation of a toe pad caused marked suppression of central pad‐evoked activity of toe extensors with a highly specific spatial pattern. The inhibition was strongest in extensors of its own toe, and gradually weaker in the more distant toes. Weak excitation was occasionally evoked in extensors of the most medial or lateral toes, when the most lateral or the most medial toe‐pad, respectively, was stimulated. 5. A similar pattern of relfex to that from the toe pad was evoked from the claw base and the hairy toe dorsum of each digit. 6. Reflex effects, both inhibitory and excitatory, from the central and toe pads, claw bases and toe dorsum were maintained during prolonged stimuli, indicating that slowly adapting receptors contributed to these reflexes. 7. It is concluded that stimulation of localized skin areas of the foot, particularly the pads, evokes highly specialized reflexes, which may be important in controlling movements of individual digits.
The effects of corticotrophin‐releasing factor and two antagonists on breathing movements in fetal sheep.
Authors: Bennet L , Johnston B M , Vale W W , Gluckman P D
Published: December 2014

1. The respiratory effects of corticotrophin‐releasing factor (CRF) and the CRF antagonists alpha‐helical CRF 9‐41 (alpha hCRF) and [DPhe 12, Nle 21‐38] rCRF (12‐41) (DPhe CRF) have been studied in unanaesthetized fetal lambs of 125‐140 days gestation. 2. CRF when given as a 10 micrograms bolus followed by a 5 micrograms h‐1 infusion into a lateral cerebral ventricle caused prolonged continuous fetal breathing movements which were stimulated in both amplitude and frequency but which did not persist during hypoxia. 3. Lower doses of CRF (20 ng bolus followed by 10 ng h‐1) increased the amplitude but not the frequency of fetal breathing movements which did not become continuous. 4. At higher doses (20 micrograms bolus followed by 10‐15 micrograms h‐1) CRF induced cerebral convulsions which were also associated with fetal breathing movements of increased amplitude and frequency. 5. The CRF antagonists alpha hCRF and DPhe CRF both inhibited fetal breathing movements and induced a prolonged apnoea which was resistant to the stimulatory effects of 5‐6% hypercapnia. 6. We conclude that CRF stimulates breathing movements in the fetal lamb. The finding that administration of the CRF antagonists alone cause apnoea suggests that CRF may have a tonic role in the regulation of fetal breathing movements.
Neuronal activity related to head and eye movements in cat superior colliculus.
Authors: Peck C K
Published: December 2014

1. Movement‐related discharges were recorded from single cells in the superior colliculus of alert cats while they made eye saccades (with head fixed) or gaze saccades (with head free). 2. Visual and auditory stimuli were used as saccade targets. In addition, saccades were made to the remembered location of targets and spontaneously, in the absence of targets, during intertrial intervals. 3. When the head was still and the cat performed either spontaneous saccades or saccades to remembered targets, only one class of tectal neurone, the saccade‐related burst neurone, inevitably discharged prior to all saccades of appropriate amplitude and direction. 4. Neurones with longer lead times and less intense presaccadic discharges were obligately linked only to visually elicited saccades. The discharge of some of these long‐lead neurones was also influenced by the spatial position of the visual target (that is, by craniotopic motor error), while that of the saccade‐related burst neurones was a function of retinocentric motor error. 5. Most neurones which discharged before head movements also discharged before eye movements and had large, contralateral movement fields.
gamma‐Aminobutyric acid responses in rat locus coeruleus neurones in vitro: a current‐clamp and voltage‐clamp study.
Authors: Osmanović S S , Shefner S A
Published: December 2014

1. Intracellular recordings were made from locus coeruleus (LC) neurones in a totally submerged brain slice preparation from adult rats. The effect of gamma‐aminobutyric acid (GABA) on LC neurones was studied under current‐clamp and voltage‐clamp conditions. GABA caused inhibition of spontaneous firing and a large conductance increase in LC neurones. These effects could be accompanied by depolarization, hyperpolarization or little change in membrane potential depending on the presence or absence of Cl‐ in the recording microelectrode. 2. The reversal potential for GABA‐induced changes in membrane potential (EGABA) was ‐71.3 +/‐ 1.1 mV (S.E.M., n = 21) in cells impaled with potassium acetate electrodes and ‐47.5 +/‐ 1.4 mV (S.E.M., n = 15) in cells impaled with KCl electrodes. When the external Cl‐ concentration was reduced EGABA was shifted in the depolarizing direction by 51.5 mV per tenfold change in external Cl‐ which is close to the shift predicted by the Nernst equation for a selective increase in CL‐ conductance. 3. GABA effects on LC neurones result from a direct action since they persist in low‐Ca2+ and high‐Mg2+ media which block synaptic transmission. 4. The effects of GABA were concentration dependent and antagonized by bicuculline (10 microM) and bicuculline methiodide (80‐100 microM) indicating that they were mediated predominantly by an action on GABAA receptors. In the presence of bicuculline, EGABA was shifted towards the K+ equilibrium potential which indicated a residual bicuculline‐resistant action at GABAB receptors. 5. GABA‐induced responses were membrane potential dependent. GABA conductance was observed to decrease with membrane hyperpolarization in a linear manner. GABA‐induced current showed outward rectification. In the voltage range studied (rest to ‐110 mV) the extent of this rectification was predicted by the Goldman‐Hodgkin‐Katz equation, suggesting that it was due to the unequal distribution of Cl‐ across the membrane. In addition, the time constant of decay of GABA current was decreased by membrane hyperpolarization; this could be due to a voltage‐dependent change in receptor or channel kinetics. 6. These data suggest that the primary action of GABA on LC neurones is to increase Cl‐ conductance by activation of bicuculline‐sensitive GABAA receptors. Due to the voltage dependence of GABA responses, GABA will exert a stronger inhibitory effect on LC neurones at depolarized than at hyperpolarized membrane potentials. This could serve as a negative feedback mechanism to control excitability of these neurones.
Cardiorespiratory effects induced by acetazolamide on the ventromedullary surface of the cat.
Authors: Andreatta‐van Leyen S , Averill D B , Guertzenstein P G
Published: December 2014

1. Inhibition of carbonic anhydrase by acetazolamide in alpha‐chloralose‐anaesthetized cats, in a region of the brain stem co‐extensive with the glycine‐sensitive area, intermediate chemosensitive area, and probably C1 catecholaminergic neurones produces hypotension, bradycardia and depression of the central respiratory drive. 2. These responses are concentration dependent, and can still be observed when the enzyme substrate (CO2) is elevated. Therefore, in both the hypercapnic and the normocapnic condition, similar responses in arterial blood pressure, heart rate and respiratory rate are observed when acetazolamide is topically applied to the glycine‐sensitive area. 3. To investigate further the contribution of peripheral baro‐, chemo‐ and cardiopulmonary receptors to these responses, acetazolamide was topically applied to the glycine‐sensitive area under three different conditions: intact gallamine‐paralysed (5 mg kg‐1 h‐1) and artificially ventilated (A), sinoaortic denervated (B), and sinoaortic denervated plus bilaterally vagotomized cats (C). Under all conditions, similar responses were observed. The fall in arterial blood pressure was 75 +/‐ 11 (A), 90 +/‐ 13 (B), and 75 +/‐ 9 mmHg (C). Changes in heart rate during acetazolamide application were ‐23 +/‐ 6, ‐20 +/‐ 8, and ‐26 +/‐ 6 beats min‐1, respectively. The decreases in respiratory rate were 9 +/‐ 2 (A), 11 +/‐ 2 (B), and 11 +/‐ 2 breaths min‐1 (C). 4. The data indicate that the responses to topical application of acetazolamide are mainly due to its central action at the glycine‐sensitive area and are not influenced by peripheral baroreceptor and chemoreceptor inputs.
Intraterminal recordings from the rat neurohypophysis in vitro.
Authors: Bourque C W
Published: December 2014

1. Intracellular recordings were obtained from neurosecretory terminals (endings of Herring bodies), axons and pars intermedia cells in the isolated neuro‐intermediate lobe of the rat. Responses to current injection and stimulation of the neural stalk (NS) were examined at 34 degrees C. Cellular identity was verified following injection of Lucifer Yellow. 2. Neurosecretory terminals were identified by a constant‐latency action potential response to NS stimulation and an appropriate collision test. This response was not blocked by Ca2(+)‐free solutions. Hyperpolarization of the terminals could block the generation of a local spike. Injection of Lucifer Yellow into eleven units confirmed that such responses were recorded from neurosecretory terminals. 3. Neurohypophysial nerve terminals had a resting potential of ‐60.4 +/‐ 1.1 mV and displayed a spike amplitude of 72.4 +/‐ 1.9 mV. The local spike threshold was ‐41.6 +/‐ 1.9 mV. Voltage‐current relations were linear near resting potential, but displayed strong outward rectification positive to ‐55 mV. While terminals could fire at high frequencies during NS stimulation, repetitive activity could not be evoked by prolonged depolarizing current pulses. 4. During the initial 1‐3 s of a train of brief depolarizing pulses or NS stimuli, nerve terminals showed a progressive broadening of their action potentials. At steady state, the duration of these impulses increased logarithmically with firing rate, showing a maximum near 25 Hz. Spike broadening in nerve terminals was reversibly abolished by superfusion of the neural lobe with Ca2(+)‐free, Mn2(+)‐containing solutions. In the absence of external Ca2+, action potentials were smaller, and lacked a prominent shoulder on their repolarizing phase. 5. Sustained (greater than 5 s) repetitive stimulation at 10‐20 Hz led to a gradual increase in the latency for invasion and eventual failure of the spike‐generating mechanism within the terminal. This effect required several seconds to recover. In contrast, action potentials recorded within the axon followed continuous repetitive stimulation and did not show any frequency‐dependent changes in duration (0.7 +/‐ 0.1 ms). 6. Cells of the pars intermedia (PI) displayed an input resistance of 215.7 +/‐ 47.4 M omega and fired a single action potential in response to current injection. The amplitude of this current‐evoked spike decreased during repetitive stimulation, but its duration was not affected. In 87% of the PI cells tested, stimulation of the NS evoked a Ca2(+)‐sensitive synaptic response which reversed near ‐40 mV, but no cell was directly activated by the stimulus.
Increasing atrial pressure during cardiac tamponade does not elevate plasma levels of the peptide ANP in conscious dogs.
Authors: Klopfenstein H S , Mathias D W , Bernath G A , Cogswell T L
Published: December 2014

1. Factors influencing the release of atrial natriuretic peptide (ANP) are not well understood. We chose a conscious euvolaemic canine model of cardiac tamponade to investigate the roles played by atrial blood pressure, transmural atrial pressure, atrial size, and arginine vasopressin (AVP) on ANP release since during cardiac tamponade the atrial transmural pressure and size decrease as atrial pressure increases. The haemodynamic response to acute cardiac tamponade in conscious dogs differs from that in anaesthetized or convalescent animals. 2. Eighteen mongrel dogs were prepared for the chronic measurement of: ascending aortic blood flow (electromagnetic flowmeter); intrapericardial, right atrial and aortic blood pressures, and the evaluation of right atrial size (two‐dimensional echocardiography). After the animals had recovered from surgery, data were collected during progressive cardiac tamponade induced by intrapericardial infusion of warmed saline (20 ml/min) to the point of haemodynamic decompensation. Decompensated cardiac tamponade (DCT) was defined as a decline in mean aortic blood pressure to 70% of the level present when the pericardial space was drained of fluid (baseline) and was produced in all animals within 25 min. Plasma ANP and AVP levels were measured at selected intervals. 3. Cardiac output decreased progressively as intrapericardial pressure, right atrial blood pressure and heart rate increased. Mean aortic blood pressure was well maintained until late in tamponade when it declined rapidly, while atrial transmural pressure and atrial size decreased continuously. These haemodynamic changes were associated with stable ANP plasma levels. There was no significant change in AVP plasma levels from the baseline level of 2.5 +/‐ 0.4 pg/ml until the point of DCT when they abruptly increased to 117 +/‐ 36.4 pg/ml. 4. The ability to increase ANP plasma levels was confirmed in a subgroup of animals by noting the response to AVP injection. Although the animals were able to increase plasma ANP levels in response to AVP injection (when intrapericardial pressure was normal) and the plasma AVP level was markedly increased late in tamponade, the time course of plasma AVP elevation could not explain why plasma ANP levels did not decrease as atrial transmural pressure and atrial size declined. 5. Thus, although atrial distention and not simply atrial blood pressure must play a dominant role in stimulating ANP release from the atria, decreased atrial size does not result in lowering of plasma ANP levels below baseline levels in this conscious euvolaemic canine model.
Depletion of intracellular free Mg2+ in Mg2(+)‐ and Ca2(+)‐free solution in the taenia isolated from guinea‐pig caecum.
Authors: Nakayama S , Tomita T
Published: December 2014

1. In isolated strips of the taenia of guinea‐pig caecum removal of Mg2+ alone from the external solution had no clear effects on contractions produced by carbachol. However, after treatment with Mg2(+)‐ and Ca2(+)‐free solution, readmission of 2.4 mM‐Ca2+ caused only limited recovery, and addition of Mg2+ was necessary for full recovery. 2. When Mg2+ was removed in the absence of Ca2+, oxygen consumption increased, but gradually decreased again in the prolonged absence of the divalent cations. The increase in O2 consumption was blocked by ouabain or by decreasing the external sodium concentration to 20 mM. 3. Under normal conditions, the intracellular free Mg2+ concentration [( Mg2+]i) was estimated to be 310 +/‐ 30 microM (n = 17) from the chemical shift of the ATP peaks obtained with 31P nuclear magnetic resonance (NMR), assuming the dissociation constant of MgATP to be 41 microM. 4. Removal of external Mg2+ did not alter [Mg2+]i within 100 min. However, when both Mg2+ and Ca2+ were omitted, [Mg2+]i decreased to 8.3 +/‐ 3.6 microM (n = 12) in 100 min. The [Mg2+]i recovered completely on readmission of 1.2 mM‐Mg2+. 5. When Mg2+ and Ca2+ were omitted, the phosphocreatine (PCr) content of the tissue slowly decreased to about 90% and the ATP concentration was reduced to about 60% of the control in 100 min. On Mg2+ readmission the ATP levels recovered partially, whereas PCr decreased further. 6. It is concluded that free [Mg2+]i slowly decreases when both Mg2+ and Ca2+ are removed from the external solution, due to an increased permeability of the plasma membrane, and that when [Mg2+]i is reduced to less than about 10% of the normal internal concentration, energy metabolism, membrane transport, and contraction are impaired.
Chloride permeability regulation via a cyclic AMP pathway in cultured human sweat duct cells.
Authors: Pedersen P S
Published: December 2014

1. Isolated coiled reabsorptive sweat ducts from normal subjects and patients with cystic fibrosis (CF) were cultured in vitro. Cells were harvested and plated onto permeable supports to form confluent cell sheets. The Ussing chamber technique was used to study pharmacological regulation of the transepithelial ion transport in these membranes. 2. Addition of a stable cyclic AMP analogue, 8‐Br‐cyclic AMP, to normal cell cultures resulted in a decrease of the transepithelial potential difference (PD). 3. Forskolin exposure resulted in a similar PD decrease, which was augmented by the phosphodiesterase inhibitor, isobutylmethylxanthine (IBMX). 4. Exposure to isoprenaline, prostaglandin E2 (PGE2), and phenylephrine resulted in a response mimicking the forskolin‐induced response, that was also amplified by IBMX. 5. Pre‐incubation with cholera toxin abolished the isoprenaline response and reduced the control resistance. 6. Propranolol abolished the responses induced by isoprenaline and phenylephrine, whereas phentolamine had no effect. PGE2‐induced responses were inert to both types of blockers. 7. Indomethazine addition to an unstimulated membrane resulted in a weak PD increase, i.e. a response opposite to that induced by isoprenaline. 8. IBMX addition to an unstimulated membrane resulted in a weak isoprenaline‐like response. When the cells were pre‐treated with indomethazine this IBMX response was absent. 9. Unidirectional Cl‐ isotope flux studies demonstrated a large increase of net Cl‐ reabsorption in response to isoprenaline and PGE2. 10. Mannitol isotope flux studies revealed that the paracellular permeability was unaffected by isoprenaline exposure. 11. Membranes derived from CF patients did not respond similarly to any of these agents. However, a weak spike, occasionally followed by a gradual increase of the short‐circuit current (Iscc), was observed in both normal subjects and CF patients. 12. It is concluded that the primary effect on ion transport of factors increasing the cyclic AMP in normal cultured sweat duct cells is an activation of a transcellular Cl‐ permeability. This effect was missing in cells derived from CF patients.
Transient electrical phenomenon of the voltage‐clamped toad urinary bladder.
Authors: Gordon L G
Published: December 2014

1. The effects of changes in voltage on the transepithelial current through the toad urinary bladder have been studied using Ussing chambers. 2. Step changes in voltage produced two transient currents of duration seconds and minutes respectively. 3. Amiloride, which was used to block all active transport, also eliminated the transient nature of the current responses, indicating that the phenomena were cellular in origin. In the presence of amiloride, amphotericin B regenerated the short‐circuit current and the transient behaviour. 4. The effects of substituting gluconate for Cl‐ in the medium were examined. Similar transient responses were observed, indicating that they were not due to changes in a plasma membrane Cl‐ conductance. 5. The shape and magnitude of the first current transient changed with (i) changes in the mucosal Na+ concentration, (ii) the magnitude of the transepithelial voltage step, (iii) the addition of antidiuretic hormone, (iv) changes in the serosal K+ concentration, or (v) the addition of ouabain. 6. The second current transient was similarly affected by such challenges. 7. In some bladders the voltage step produced current oscillations similar to those obtained after the epithelium had been challenged with a serosal osmotic step (Gordon, 1988). 8. The results suggest that two major processes are initiated by a transepithelial voltage step. The first involves a change in the K+ conductance of the basolateral membrane and the second is associated with the alteration of cellular ion content and Na+ pump rate.
Mechanism of intestinal fatty acid uptake in the rat: the role of an acidic microclimate.
Authors: Shiau Y F
Published: December 2014

1. Micellar solubilization of lipolytic products is an important step in lipid absorption. However, micelles are not absorbed intact; dissociation of lipolytic products from bile salt micelles must occur. The dissociation of micelles has been postulated to occur in an acidic microclimate. 2. The effect of an acidic microclimate on the uptake of micellar fatty acid was examined in the rat intestine. We reported that the presence of a lower pH microclimate is associated with a higher fatty acid uptake, suggesting that a lower pH enhances fatty acid uptakes from the micelles. 3. Fatty acid uptake from solutions containing a constant amount of bile salt (10 mM) and varying amounts of fatty acid (3.3‐26.4 mM) revealed a saturation phenomenon which reflects the fatty acid carrying capacity of a 10 mM‐taurocholate solution. 4. There was a linear relationship between fatty acid uptake and fatty acid concentration when the micellar solutions contained a constant ratio of fatty acid and taurocholate (1.32). 5. Our results indicate that the fatty acid carrying capacity of the micelle and the number of micelles in the solution are both important determinants for the amount of fatty acids delivered to the microclimate. The amount of fatty acids derived from the dissociation of micelles within the microclimate determines fatty acid uptake by the intestine.
Urinary and proximal tubule acidification during reduction of renal blood flow in the rat.
Authors: Jaramillo‐Juárez F , Aires M M , Malnic G
Published: December 2014

1. The effects of reduction in renal blood flow (RBF) on urinary acidification and proximal tubule H+ ion secretion were studied after partial aortic clamping in rats. 2. Acute reduction of the renal perfusion pressure (from 109 +/‐ 3.88 to 77.4 +/‐ 1.05 mmHg) decreased both inulin and PAH (p‐aminohippurate) clearances to about one‐third of their control values. Absolute levels of urinary sodium excretion also decreased markedly, but fractional sodium excretion did not change significantly. 3. Urine pH and bicarbonate levels were not affected, but titratable acidity increased significantly from 0.12 +/‐ 0.011 to 0.25 +/‐ 0.042 muequiv min‐1 ml‐1 glomerular filtration rate (GFR). During aortic clamping, cortical PCO2 as determined by means of Severinghaus microelectrodes was reduced by a mean value of 7.0 +/‐ 1.5 mmHg. 4. Proximal tubule acidification kinetics were studied by stationary microperfusion techniques in which the time course of pH changes was monitored by pH microelectrodes. Steady‐state pH fell from a mean control value of 6.77 +/‐ 0.03 to 6.65 +/‐ 0.02, and stationary bicarbonate concentrations from 4.70 +/‐ 0.27 to 2.84 +/‐ 0.18 mM. Acidification half‐time decreased from 5.07 +/‐ 0.30 to 4.39 +/‐ 0.19 s, and net bicarbonate reabsorption increased from 1.63 +/‐ 0.14 to 1.99 +/‐ 0.12 nmol cm‐2 s‐1, these changes being statistically significant. 5. The experiments demonstrate that both overall acid excretion and proximal acid secretion are not compromised by a large decrease of RBF to about one‐third of the control value; titratable acid excretion and proximal net bicarbonate reabsorption were even moderately increased under these conditions.
Inositol trisphosphate mediates cloned muscarinic receptor‐activated conductances in transfected mouse fibroblast A9 L cells.
Authors: Jones S V , Barker J L , Goodman M B , Brann M R
Published: December 2014

1. The mechanism by which cloned m1 and m3 muscarinic receptor subtypes activate Ca2+‐dependent channels was investigated with whole‐cell and cell‐attached patch‐clamp recording techniques and with Fura‐2 Ca2+ indicator dye measurements in cultured A9 L cells transfected with rat m1 and m3 cDNAs. 2. The Ca2+‐dependent K+ and Cl‐ currents induced by muscarinic receptor stimulation were dependent on GTP. Responses were reduced when GTP was excluded from the intracellular recording solution or when GDP‐beta‐S was added. Intracellular GTP‐gamma‐S activated spontaneous fluctuations and permitted only one acetylcholine‐(ACh) induced current response. These results implicate GTP‐binding proteins (G protein) in the signal transduction pathway. This G protein is probably not pertussis toxin‐sensitive as the ACh‐induced electrical response was not abolished by pertussis toxin treatment. 3. Cell‐attached single‐channel recordings revealed activation of ion channels within the patch during application of ACh outside the patch, implying that second messengers might be involved in the ACh‐induced response. Two types of K+ channel were activated, a discrete channel of 36 pS and channel activity calculated to be about 5 pS. 4. Application of 8‐bromo cyclic AMP or 1‐oleoyl‐1,2‐acetylglycerol (OAG) produced no electrical response and did not affect the ACh‐induced responses. Phorbol myristic acetate (PMA) evoked no electrical response, but reduced the ACh‐induced responses. 5. Inclusion of inositol 1,4,5‐trisphosphate (IP3) in the intracellular pipette solution activated outward currents at ‐50 mV associated with an increase in conductance. The IP3‐induced current response reversed polarity at ‐65 mV and showed a dependence on K+. Increasing the intracellular free Ca2+ concentration ([Ca2+]i) from 20 nM to 1 microM also induced an outward current response associated with an increase in conductance. Inclusion of inositol 1,3,4,5‐tetrakisphosphate (IP4) in the intracellular solution had no effect on the A9 L cells. 6. Fura‐2 measurements revealed ACh‐induced increases in Cai2+. The Ca2+ responses were abolished by atropine showing that they were muscarinic in nature. Removal of extracellular Ca2+ did not affect the initial ACh‐induced increase in Cai2+ but subsequent Cai2+ responses to ACh were depressed, suggesting depletion of Ca2+ intracellular stores. Residual though small responses continued to be elicited by ACh. Barium (5 mM) had little effect and cobalt slightly reduced the ACh‐induced Ca2+ response. 7. The ACh‐induced currents recorded at ‐50 mV were unaffected by removal of extracellular Ca2+.(ABSTRACT TRUNCATED AT 400 WORDS)
Fastigial inputs to paraventricular neurosecretory neurones studied by extra‐ and intracellular recordings in rats.
Authors: Katafuchi T , Koizumi K
Published: December 2014

1. The effects of stimulation of the cerebellar fastigial nucleus (FN) on the activity of neurosecretory neurones in the hypothalamic paraventricular nucleus (PVN) of rats, anaesthetized with urethane and alpha‐chloralose, were investigated by extracellular and intracellular recordings. 2. With extracellular recording, 139 PVN neurosecretory neurones were identified by antidromic activation following stimulation of the pituitary stalk, of which 120 were spontaneously firing and 19 were silent. Three types of responses to FN stimulation (1 or 2 pulses at 333 Hz) were observed in 43% of spontaneously firing PVN neurosecretory neurones: inhibition (type I) with a latency of 4.3 +/‐ 4.1 ms (mean +/‐ S.D., 32 of 120 neurones, 27%); excitation (type E) with 22.3 +/‐ 8.1 ms latency (14 of 120, 11%); and inhibition‐excitation type (I‐E) with 5.5 +/‐ 3.4 ms latency (6 of 120, 5%). Silent neurosecretory neurones did not respond to FN stimulation. Twelve per cent of non‐neurosecretory cells (three out of twenty‐six tested) responded to FN stimulation (one was inhibited, and two were excited). 3. Repetitive stimulation (60 Hz, 10 s) of the FN, which evoked a stimulus‐locked pressor response, suppressed on‐going activity of PVN neurosecretory neurones in 43% (twenty‐nine of sixty‐eight) of neurones tested. In 40% of these neurones, the activity was also inhibited by intravenous injection of phenylephrine (3 micrograms in 0.3 ml Ringer solution), while in other neurones the injection had no effect. Rebound excitation of neurone activity lasting for 1‐5 min after termination of repetitive stimulation was observed in 28% of the neurones. Ten neurones (14%) were excited by repetitive stimulation. 4. Successful intracellular recordings were made from seventy‐two PVN neurones, of which thirty‐seven were neurosecretory cells. The mean resting membrane potential was ‐51 mV (n = 72; range from ‐40 to ‐75 mV). The input resistance of neurosecretory cells was 117 +/‐ 21 M omega (range 93‐153 M omega; n = 8). This value was higher than that for non‐neurosecretory cells which was found to be 53 +/‐ 10 M omega (range 35‐72 M omega; n = 9). The difference was statistically significant (P less than 0.01, Student's t test). 5. In response to FN stimulation, sixteen (43%) of the thirty‐seven neurosecretory neurones showed IPSPs with latencies of 7.4 +/‐ 2.8 ms and three (8%) exhibited EPSPs with latencies of 13.3 +/‐ 4.2 ms.(ABSTRACT TRUNCATED AT 400 WORDS)
Human muscle spindle response in a motor learning task.
Authors: Vallbo A B , al‐Falahe N A
Published: December 2014

1. Impulse discharge of single muscle spindle afferents from the finger extensor muscles was recorded in the radial nerve of conscious human subjects, during a motor learning task engaging the metacarpo‐phalangeal joint of a single finger, using the microneurography technique. 2. Subjects were requested first to pay attention to a complex sequence of imposed single joint movements, and immediately afterwards to reproduce actively the same sequence. No external load was added to the finger and visual control was denied altogether so that subjects relied on mechanoreceptor input exclusively for the sampling and reproduction of movement. In addition, sequences of imposed movements were delivered while subjects were not attending in order to allow analysis of the attention effect. 3. The response of the individual unit was uniform in repeated tests. There were clear differences between spindle firing rate in imposed and actively reproduced movements with most units. However, the difference was complex during the individual sequence, in that firing rate was usually higher during periods of reproduced movements when the muscle was relatively short whereas it was identical when the muscle was relatively long. 4. The hypothesis that reproduction and verification of an imposed movement may be based on simple matching between identical spindle firing in imposed and active movements, was difficult to reject altogether because identical spindle input was present during considerable sections of the movement sequence. It may be speculated that agonists and antagonists cover different ranges of joint excursion, with identical spindle firing rates in imposed and reproduced movements. 5. Attention to imposed movements was associated with a minute and inconsistent increase of spindle firing rate in some afferents and then usually with a slight increase of EMG activity of the parent muscle as well. 6. It was concluded that focusing attention on the kinaesthetic input during imposed movement was not associated with a consistent increase of fusimotor drive.
The effects of tetracaine on charge movement in fast twitch rat skeletal muscle fibres.
Authors: Hollingworth S , Marshall M W , Robson E
Published: December 2014

1. The effects of tetracaine, a local anaesthetic that inhibits muscle contraction, on membrane potential and intramembrane charge movements were investigated in fast twitch rat muscle fibres (extensor digitorum longus). 2. The resting membrane potentials of surface fibres from muscles bathed in isotonic Ringer solution containing 2 mM‐tetracaine were well maintained, but higher concentrations of tetracaine caused a time‐dependent fall of potential. Muscle fibres bathed in hypertonic solutions containing 2 mM‐tetracaine were rapidly depolarized. In both isotonic and hypertonic solutions, the depolarizing effect of tetracaine could not be reversed. 3. Charge movement measurements were made using the middle‐of‐the‐fibre voltage clamp technique. The voltage dependence of charge movements measured in cold isotonic solutions was well fitted by a Boltzmann distribution (Q(V) = Qmax/(1 + exp(‐(V‐V)/k] where Qmax = 37.3 +/‐ 2.8 nC muF‐1, V = ‐17.9 +/‐ 1.2 mV and k = 12.6 +/‐ 0.8 mV (n = 6, 2 degrees C; means +/‐ S.E. of means). Similar values were obtained when 2 mM‐tetracaine was added to the isotonic bathing fluid (Qmax = 40.6 +/‐ 2.3 nC microF‐1, V = ‐14.1 +/‐ 1.3 mV, k = 15.3 +/‐ 0.8 mV; n = 8, 2 degrees C). 4. Charge movements measured around mechanical threshold in muscle fibres bathed in hypertonic solutions were reduced when 2 mM‐tetracaine was added to the bathing fluid. The tetracaine‐sensitive component of charge was well fitted with an unconstrained Boltzmann distribution which gave: Qmax = 7.5 nC microF‐1, V = ‐46.5 mV, k = 5.5 mV. The e‐fold rise of the foot of the curve was 9.3 mV.
Effects of hypoxia upon contractions evoked in isolated rabbit pulmonary artery by potassium and noradrenaline.
Authors: Marriott J F , Marshall J M
Published: December 2014

1. Comparisons have been made between rabbit thoracic aorta and main pulmonary artery of the effects of hypoxia upon contractions evoked by noradrenaline (NA) and KCl (K+). 2. Contractions were evoked in cylindrical sections of pulmonary artery and aorta, mounted for isometric recording of tension, by NA and K+ (at ED80) in normoxia (PO2 110 mmHg) and hypoxia (PO2 23 or 7 mmHg). Contractions were also evoked in Ca2(+)‐free conditions with EGTA to prevent influx of extracellular Ca2+. All contractions are expressed as a percentage of normoxic response in the presence of Ca2+. 3. Potassium‐evoked contractions of aorta and pulmonary artery were reduced to a similar extent by both levels of hypoxia, to 85 and 92% respectively. As expected K(+)‐evoked contractions were virtually abolished by Ca2(+)‐free conditions. It is proposed that hypoxia has a small inhibitory effect upon contraction mediated by Ca2+ influx via voltage‐operated Ca2+ channels. 4. In the aorta in the presence of Ca2+, hypoxia reduced NA‐evoked contractions to 84% at PO2 23 mmHg and 34% at PO2 7 mmHg. In the absence of Ca2+, NA‐evoked contractions reached 73% in normoxia, but only 43 and 21% at PO2 23 and 7 mmHg respectively. These results suggest that hypoxia reduces the component of contraction that is mediated by release of intracellular Ca2+ and possibly that mediated by agonist‐induced Ca2+ influx. 5. In the pulmonary artery also, NA‐evoked responses in the absence of Ca2+ were reduced from 60% in normoxia, to 49 and 38% at PO2 23 and 7 mmHg. But, in the presence of Ca2+, hypoxia potentiated NA‐evoked contractions to 113 and 111% at PO2 23 and 7 mmHg respectively. It is proposed that in the pulmonary artery, hypoxia reduces the component of contraction mediated by release of intracellular Ca2+, but facilitates that mediated by extracellular Ca2+. Possible mechanisms are discussed.
Analysis of excitatory synaptic action in pyramidal cells using whole‐cell recording from rat hippocampal slices.
Authors: Hestrin S , Nicoll R A , Perkel D J , Sah P
Published: December 2014

1. The pharmacological and biophysical properties of excitatory synapses in the CA1 region of the hippocampus were studied using patch electrodes and whole‐cell recording from thin slices. 2. Excitatory postsynaptic currents (EPSCs) had a fast component whose amplitude was voltage insensitive and a slow component whose amplitude was voltage dependent with a region of negative slope resistance in the range of ‐70 to ‐30 mV. 3. The voltage‐dependent component was abolished by the N‐methyl‐D‐aspartate (NMDA) receptor antagonist DL‐2‐amino‐5‐phosphonovalerate (APV; 50 microM), which had no effect on the fast component. Conversely, the fast voltage‐insensitive component was abolished by the non‐NMDA receptor antagonist 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX; 10 microM) which had no effect on the slow component. 4. In Ringer solution with no added Mg2+ the current‐voltage relation of the NMDA component was linear over a much larger voltage range than in the presence of 1.3 mM‐Mg2+. 5. The NMDA component of the EPSC could be switched off with a hyperpolarizing voltage step at the soma. The kinetics of this switch‐off was used to estimate the speed of clamp control of the subsynaptic membrane as well as the electrotonic distance from the soma. The kinetic analysis of the EPSC was restricted to synapses which were judged to be under adequate voltage control. 6. For those synapses that were close to the soma the time constant for decay for the non‐NMDA component, which was voltage insensitive, ranged from 4‐8 ms. 7. The rise time for the NMDA component was 8‐20 ms and the time constant for decay ranged from 60‐150 ms. 8. During increased transmitter release with post‐tetanic potentiation or application or phorbol esters, both components of the EPSC increased to a similar extent. 9. These experiments provide a detailed description of the dual receptor mechanism operating at hippocampal excitatory synapses. In addition, the experiments provide an electrophysiological method for estimating the electrotonic distance of synaptic inputs.