bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gastric emptying and secretion in the calf on duodenal infusion of tryptophan, tryptamine and 5‐hydroxytryptamine
Authors: Bell F. R. , Webber D. E. 
Published: December 2014

1. Gastric emptying, gastric acid and pepsinogen secretion were assessed simultaneously in the conscious calf using the test meal and duodenal perfusion technique (Bell & Mostaghni, 1975).2. When 60 m
M‐HCl was infused into the duodenum, gastric emptying was arrested but both acid and pepsinogen secretion continued at a low level. Duodenal infusion with isotonic NaHCO3 caused rapid exponential emptying of the test meal and acid and pepsinogen output was more than doubled.3. Duodenal infusion of amino acids in isotonic NaHCO3 did not affect the rapid emptying, except infusion with tryptophan, which caused a measureable degree of inhibition of emptying, with concomitant effects on acid and pepsinogen secretion4. Tryptamine and 5‐hydroxytryptamine (5‐HT) incorporated in low concentration into isotonic NaHCO3 also produced depression of gastric emptying, acid and pepsinogen levels comparable to the response initiated by acid infusate. Tryptophan was effective only in non‐physiological amounts while 5‐HT and tryptamine were active in smaller doses.5. Our results suggest that the inhibition of gastric emptying following duodenal infusion of tryptophan noted by Stephens, Woolson & Cooke (1975) may be due to the duodenal synthesis of its biogenic amine derivatives tryptamine and 5‐HT.6. The level of activity of the three gastric functions, emptying, acid secretion and pepsinogen secretion appears to be linked. A single stimulus, therefore, could evoke a duodenal receptor or receptors to mediate or suppress activity of the gastric smooth muscle and secretory cells through interrelated mechanisms. The effect of some duodenal infusates, however, produces some variability in response which suggests differential activation of different receptors with consequent variable motor activity on effector cells.
Distribution of inulin, sucrose and mannitol in rat brain cortex slices following in vivo or in vitro equilibration
Authors: Amtorp Ole 
Published: December 2014

1. The distribution spaces of inulin, sucrose and mannitol in rat brain cortex slices were determined in tracer experiments. Tracer equilibration times of 5 hr were used with combined ventriculo‐cisternal perfusion and
I.V. infusion of tracers. After 5 hr of equilibration the distribution volumes (expressed as μl./100 mg wet wt.) obtained using the perfusion fluid as reference and after correction of tracer amount in residual blood were obtained. Information on cellular uptake was obtained by examining a slow component of wash‐out curves from brain slices after in vivo equilibration. Distribution spaces were corrected for intracellular penetration to obtain the extracellular volumes of distribution. Inulin was found to equilibrate with 13·3 μl. extracellular tissue water per 100 mg initial wet weight, sucrose with 16·6 μl. and mannitol with 19·5 μl.2. Marker spaces in rat brain cortex slices were also analysed by compartmental analysis of efflux of tracer inulin, sucrose and mannitol following in vitro incubation in a balanced medium for 60 min. Following in vitro equilibration, inulin was found to equilibrate with 22·4 μl. extracellular tissue water per 100 mg of final wet weight, sucrose to equilibrate with 31·7 μl. extracellular tissue water and mannitol with 42·3 μl.3. Inulin space in vitro when allowance is made for swelling produced during incubation of the slice was similar to the chemically delineated extracellular distribution volume in vivo. Sucrose and mannitol spaces in vitro, however, did not accord with in vivo determinations, most likely due to access of markers to areas of cell damage in the slice arisen during incubation.4. Comparison of fluid spaces delineated by inulin in slices of rat cerebral cortex following in vivo and in vitro equilibration indicated that swelling produced during incubation in vitro mainly occurred in the extracellular space. Swollen glial cells may account for the small, but significant intracellular swelling in incubated slices.
Behaviour of the rod network in the tiger salamander retina mediated by membrane properties of individual rods
Authors: Attwell David , Wilson Martin 
Published: December 2014

1. The spread of electrical signals between rods in the salamander retina was examined by passing current into one rod and recording the voltage responses in nearby rods. Rod network behaviour, measured in this way, was simulated from data on rod membrane properties gathered in voltage‐clamp experiments on single isolated rods.2. The network voltage responses to square current pulses became smaller, more transient, and had a longer time‐to‐peak, for rods further away from the site of current injection. Depolarizing currents produced smaller responses than hyperpolarizing currents of the same magnitude.3. Neighbouring rods and cones were coupled less strongly than neighbouring rods.4. The response of the rod network to current injection was unaffected by 2 m
m‐aspartate−, which eliminates transmission from receptors to horizontal cells.5. The input resistance of single isolated rods, measured at the resting potential, varied between 100 and 680 MΩ. The lower values were probably due to damage by the micro‐electrodes. Electrical coupling was found to be very strong between the rod inner and outer segments.6. A strong ‘instantaneous’ outward rectification seen in isolated rods at potentials positive to ‐35 mV was reduced, but not abolished, by 15 m
m‐TEA.7. In normal solution, isolated rods exhibited a voltage‐ and time‐dependent current, IA, whose kinetics were approximated by a single first‐order gating variable, and whose activation curve spanned the range between ‐40 and ‐80 mV. The time constant for the current varied with voltage and was 60‐200 msec between ‐140 and ‐40 mV.8. A reversal potential for IA could not be found between ‐140 and ‐40 mV in normal solution, and the fully activated current, ĪA, was approximately voltage‐independent, with a magnitude of ∼ 0.1 nA over this potential range.9. By several criteria, IA behaved as a single inward current activated by hyperpolarization. Pharmacological studies suggest, however, that it is the sum of at least two currents with very similar kinetics.10. Most isolated rods exhibited a very slow (τ ∼ 3 sec) increase in net outward current on depolarizing beyond ‐35 mV. The magnitude of this current varied considerably between cells.11. Assuming that the rod network can be approximated by a square lattice of individual rods, resistively coupled together, the voltage‐clamp data on isolated rods were used to predict the response of the network to current injection at one cell. The theoretical and observed network behaviour were in good agreement. The resistance coupling neighbouring rods was estimated to be ∼ 300 MΩ. The current IA plays a major role in determining the behaviour of the rod network.12. The time‐dependent current, IA, is responsible for the peak—plateau wave form of the response to a bright flash. A current similar to IA could also account for the negative propagation velocity of the peak of the dim flash response, through the rod network of the turtle, observed by Detwiler, Hodgkin & McNaughton (1978).
Response of soleus Ia afferents to vibration in the presence of the tonic vibration reflex in the decerebrate cat
Authors: Clark F. J. , Matthews P. B. C. , Muir R. B. 
Published: December 2014

1. Micro‐electrode recordings were made from single Ia afferents in the intact nerve to the soleus muscle in the decerebrate cat while the muscle was developing a tonic vibration reflex. This was done in order to test how effectively the afferents were excited by the vibration, and to see if any insecurity in driving might be related to tremor.2. When the amplitude of vibration was 50 μm, and the tonic vibration reflex was reasonably well developed (> 1 N of active tension) all but one of forty‐four Ia afferents were driven 1:1 by the vibration. Most were still driven by 30 μm vibration. The vibration, consisting of a train of discrete pulses at 150 Hz, was applied longitudinally in combination with a stretch of 1 mm to make the muscle taut.3. If the reflex was poorly developed (active tension < 1 N) the driving was on average less secure. However, fourteen of eighteen afferents then studied were still driven 1:1 by 50 μm vibration. The lower level of excitation by vibration was thought to be due to a deficiency of spontaneous fusimotor activity, because stroking the cat's tail or other similar gentle manipulation led each of the three misbehaving afferents so tested to be driven securely by 50 μm vibration; at the same time the reflex tension increased.4. Additional, indirect evidence favouring widespread security of Ia driving by 50 μm vibration in the presence of the reflex was obtained by modulating the amplitude of the 150 Hz vibration with a 7‐10 Hz square wave and detecting any tension fluctuations at that frequency by spectral analysis. Small degrees of modulation (e.g. < 10%) produced little if any effect, although larger depths of modulation had a powerful action.5. When the amplitude of vibration was reduced to permit insecure driving but still to elicit a reflex response, the fluctuations in Ia firing pattern were unlike those previously seen in the de‐efferented muscle. Spectral analysis showed that these firing fluctuations bore a general similarity to the tremor in the same preparation, but measurement of coherence demonstrated that the tremor and Ia firing were not well related. This was probably because individual Ia afferents were primarily influenced by local factors, and provides further evidence against the tremor of this preparation being attributable to the action of the stretch reflex.
A comparison of binocular depth mechanisms in areas 17 and 18 of the cat visual cortex
Authors: Ferster David 
Published: December 2014

1. The retinal disparity sensitivity of neurones in areas 17 and 18 of the cat visual cortex was examined. The response of each cell to an optimally oriented slit was measured as disparity was varied orthogonally to the receptive field orientation. Eye movements were monitored with a binocular reference cell simultaneously recorded in area 17 (Hubel & Wiesel, 1970).2. Two types of disparity‐sensitive cells were found, similar to those observed in the monkey by Poggio & Fischer (1977). The first type, tuned excitatory cells, were usually binocular and had a sharp peak in their disparity—response curve. They responded maximally at the disparity that brought their receptive fields into superposition on the tangent screen. This disparity closely coincided with the disparity at which the reference cell's receptive fields were also superimposed. By analogy with the monkey this point was taken to be the fixation point, or 0°. The second type, near and far cells, were most often monocular. They gave their weakest response (which was usually no response at all) at 0°. On one side of 0° the response grew linearly for up to 4° and then remained at the maximum. On the other side of zero, it remained at the minimum for up to several degrees before rising towards the maximum.3. The receptive field organization of several disparity‐sensitive cells was examined using the activity profile method of Henry, Bishop & Coombs (1969). The size and strength of the discrete excitatory and inhibitory regions of the receptive fields of a cell could quantitatively account for the shape of its disparity—response curve.4. The laminar distribution of disparity sensitivity as well as of several other receptive field properties in areas 17 and 18 was studied. The organization of the two areas was remarkably similar in many respects. There was a difference, however, in the proportions of the two types of disparity‐sensitive cells in the two areas. Area 17 contained many more tuned excitatory cells than near and far cells, while area 18 had the reverse distribution. In addition, the cells in area 18 were sensitive to a much broader range of disparities. While both areas contain disparity‐sensitive neurones, these differences suggest that they play different roles in depth vision.5. Recent psychophysical and neurophysiological evidence has led to a new model of stereopsis in which depth is signalled by the pooled activity of large groups of cells (Richards, 1971). The current results are consistent with this model.
Gastric acid response to pylorus ligation in rats: is gastrin or histamine involved?
Authors: Alumets J. , Ekelund M. , Håkanson R. , Hedenbro J. , Rehfeld J. F. , Sundler F. , Vallgren S. 
Published: December 2014

1. Pylorus ligation stimulated the acid output in vagally intact rats. The serum gastrin concentration and the gastric mucosal histamine content were not affected. The gastric histidine decarboxylase activity was initially slightly elevated and then greatly reduced (12‐20 hr after ligation).2. Pylorus ligation stimulated the acid output in chronically, but not in acutely, vagotomized rats. Chronic vagotomy raises the serum gastrin concentration, the gastric histamine content and histidine decarboxylase activity. The serum gastrin concentration was further raised by pylorus ligation. The histamine content was initially lowered but returned to preligation values after 20 hr. The histidine decarboxylase activity first decreased, but increased to very high levels 5‐6 hr after ligation. Twelve hours after ligation it was lower than before ligation.3. Following pylorus ligation pentagastrin and histamine stimulated the acid output in vagally intact and in acutely vagotomized but not in chronically vagotomized rats. By contrast, pentagastrin raised the histidine decarboxylase activity in vagally intact and in chronically vagotomized, but not in acutely vagotomized rats.4. The two major populations of endocrine cells of the oxyntic gland area (ECL cells and A‐like cells) are argyrophil, store histamine and are capable of taking up exogenous DOPA and of decarboxylating it to dopamine which is retained in the cytoplasm for several hours. As evidenced by light and fluorescence microscopy pylorus ligation did not affect their argyrophilia or their ability to produce and store dopamine.5. Pylorus ligation caused ultrastructural changes in the gastrin cells of the pyloric gland area and in the histamine‐storing ECL and A‐like cells of the oxyntic gland area. The two endocrine cell types in the oxyntic gland area were enlarged by pylorus ligation, more so after 16 hr than after 4 hr. The size of the gastrin cells seemed unaffected. In all three cell types pylorus ligation reduced the number of cytoplasmic granules. There was no increase in the Golgi area or in the endoplasmic reticulum in any of the endocrine cell types of the oxyntic gland area. It appears unlikely that the ultrastructural changes of the ECL and A‐like cells reflect an increased rate of histamine mobilization.6. The acid response to pylorus ligation probably reflects neuronal reflex mechanisms exclusively. There is no evidence that gastrin or histamine released from gastric endocrine cells mediate the response.
Feline cerebral veins and arteries: comparison of autonomic innervation and vasomotor responses
Authors: Edvinsson Lars , McCulloch James , Uddman Rolf 
Published: December 2014

1. The innervation of feline cerebral (pial) vessels by nerve fibres containing noradrenaline, substance P or vasoactive intestinal polypeptide (VIP) has been examined using the Falck—Hillarp histo‐fluorescence method and immunohistochemical techniques. Cerebral veins were shown to be innervated by nerve fibres containing noradrenaline, substance P or VIP. Nerve fibres containing noradrenaline were the most numerous, while fibres containing substance P were observed least frequently in both types of vessel. For each putative neurotransmitter, the density of the innervation of the cerebral veins was less than that of cerebral arteries.2. The vasomotor responses of individual pial arteries and veins on the convexity of the cerebral cortex to perivascular micro‐injection of noradrenaline, substance P and VIP were examined in twenty‐five cats anaesthetized with α‐chloralose.3. The perivascular micro‐application of noradrenaline resulted in pronounced dose‐dependent reductions in the diameter of pial veins (maximum calibre reduction: 32±3% noradrenaline 10−5 M) and arteries (22±3% noradrenaline 10−5 M). Pial veins were more sensitive to noradrenaline than were pial arteries tested under similar conditions. The reductions in the diameter of cerebral veins and arteries resulting from the administration of noradrenaline could be attenuated by the concomitant micro‐application of phentolamine (10−6 M).4. The perivascular micro‐application of substance P effected significant dose‐dependent increases in the calibre of pial veins (maximum calibre increase: 16±4% substance P 10−7 M) which were of a similar magnitude to those observed in pial arteries in response to this peptide (21±4% substance P 10−6 M).5. The perivascular micro‐application of VIP resulted in small increases in the calibre of pial veins (maximum calibre increase: 9±2% VIP 10−8 M) which were proportionately smaller than those observed in pial arteries in response to this peptide (23±5% VIP 10−7 M).
Slowing effects of dopamine and calcium‐channel blockers on frequency of sodium spikes in rat pars intermedia cells
Authors: Douglas W. W. , Taraskevich P. S. 
Published: December 2014

1. Spontaneous discharge of action potentials (Na spikes) in cells isolated from rat pars intermedia was slowed or arrested by Co2+, Ni2+ or Mn2+, which block voltage‐dependent Ca channels in these cells. The amplitude of persisting spikes was undiminished. The effects resembled those of dopamine.2. Action potential frequency decreased when the Ca2+ concentration was lowered to 0·1 mM and increased when the Ca2+ concentration was raised from this level to 1 mM or 2 mM or when Ba2+ (2 mM) was introduced. These effects, together with those of Co2+, Ni2+ and Mn2+, are consistent with the possibility that Ca2+ participates in the regulation of spike discharge.3. Verapamil, methoxyverapamil (D600), and nifedipine reduced the amplitude of the individual Na spikes in concentrations that had little effect on voltage‐dependent Ca channels. Action potential frequency was comparatively little affected by these drugs.4. K+ (15 mM) stimulated action potential frequency and this effect too was suppressed by dopamine or Co2+.5. The effect which dopamine had of slowing spontaneous discharge, like the inhibitory effect on secretion, was blocked by metoclopramide. But otherwise the mechanism is unclear: dopamine blocked voltage‐dependent Ca channels in some cells but not in most others.6. The effects of K+ and Ba2+ of eliciting spikes, the suppression of Na‐spike discharge by Co2+ and related Ca‐channel blocking cations, and the unspecific effects of the organic ‘Ca channel blockers’, all have implications for the use of these substances as tools to analyse stimulus—secretion coupling.
Feed‐forward dendritic inhibition in rat hippocampal pyramidal cells studied in vitro
Authors: Alger B. E. , Nicoll R. A. 
Published: December 2014

1. Intracellular recordings from CA1 pyramidal cells in the rat hippocampal slice preparation have been used to study the neuronal pathways involved in hippocampal synaptic inhibition.2. When direct comparisons are made in a single pyramidal cell, orthodromic stimulation delivered to stratum (s.) radiatum in normal recording conditions is found to be more effective than antidromic stimulation in producing inhibitory post‐synaptic potentials (i.p.s.p.s).3. Orthodromic i.p.s.p.s in normal conditions appear to be complex, multiphasic events, whereas antidromic i.p.s.p.s are relatively simple. The orthodromic i.p.s.p. involves both a GABA‐mediated dendritic component and a non‐GABA‐mediated component neither of which is activated by antidromic stimulation.4. Barbiturates induce a late depolarizing phase of the orthodromic response, a ‘depolarizing i.p.s.p.’, which is mediated by GABA. The depolarizing i.p.s.p. is not produced by antidromic stimulation.5. Injections of tetrodotoxin and bicuculline methiodide localized to either somatic or apical dendritic regions reveal that the depolarizing i.p.s.p. is produced by GABA released from neuronal elements in the dendritic field which acts on pyramidal cell dendrites.6. The depolarizing i.p.s.p. is strongly temperature‐dependent and increases in amplitude and duration progressively as slices are cooled from 37 to 22 °C.7. Depolarizing i.p.s.p.s can be produced by orthodromic stimulation in s. oriens as well as in s. radiatum. In each case the depolarizing i.p.s.p.s appear localized to the dendrites in the field stimulated.8. We conclude that the depolarizing i.p.s.p. evident in the presence of barbiturates is caused by the same synaptic release of GABA which in normal conditions produces hyperpolarizing dendritic i.p.s.p.s.9. Numerous comparisons between orthodromic and antidromic stimulation indicate that dendritic i.p.s.p.s are activated by feed‐forward pathways.
Pharmacological evidence for two kinds of GABA receptors on rat hippocampal pyramidal cells studied in vitro
Authors: Alger B. E. , Nicoll R. A. 
Published: December 2014

1. The rat hippocampal slice preparation has been used in conjunction with intracellular recording and ionophoresis to study the action of γ‐aminobutyric acid (GABA) on CA1 pyramidal cells.2. GABA elicits a hyperpolarizing (h.) response at the soma. The reversal potential of this h. response is the same as for inhibitory post‐synaptic potentials (i.p.s.p.s) evoked by stimulating pyramidal cell axons.3. GABA elicits primarily depolarizing (d.) responses when applied to the apical dendrites, but h. responses can also be found.4. The GABA antagonists bicuculline methiodide, picrotoxin, penicillin, and pentylenetetrazole are all ten to one hundred times more potent on the d. response than on the h. response. Hyperpolarizing responses are uncovered in the dendrites when intermediate doses of these drugs block the d. response.5. The GABA analogue, 4,5,6,7‐tetrahydroisoxazolo [5,4‐c]pyridine‐3‐ol (THIP), which has been proposed to activate synaptic receptors preferentially in other systems, elicits h. responses in the dendrites. It is one seventh as potent as GABA in eliciting d. responses.6. Pentobarbitone enhances d. responses to a much greater extent than h. responses, while diazepam enhances h. responses to a greater extent.7. Nipecotic acid, low temperature, and low sodium media all increase the size of d. responses to ionophoretically applied GABA indicating that an active uptake process limits their size.8. We conclude that h. responses reflect the activation of synaptic receptors which are highly concentrated on the pyramidal cell soma—initial segment, but are also present on the dendrites. Depolarizing responses, which are evoked in the dendrites, reflect the activation of extrasynaptic receptors.9. We propose that an ordinarily undetectable amount of synaptically released GABA can ‘spill’ over onto extrasynaptic (d.) receptors. Depolarizing receptor activation can be detected in the presence of pentobarbitone. Spillover is markedly enhanced at subphysiological temperatures presumably due to enhanced release of GABA and impairment of the GABA uptake system.