bluuebunny/crossref_metadata_2025 huggingface dataset:
Characteristics and tachyphylaxis of gastrin‐stimulated gastric acid secretion in the cat.
Authors: Hirst B H , Labib L A , Reed J D
Published: December 2014

1. The characteristics of gastrin‐stimulated gastric acid secretion were investigated in conscious cats fitted with chronic cannulated gastric fistulae, with particular reference to tachyphylaxis. 2. There is a significant postive correlation between the peak acid secretion in response to pentagastrin 8 microgram kg‐1 hr‐1 and body weight. Male cats secret significantly greater amounts of acid in response to pentagastrin than females. The difference is lessened, but not eliminated, by expressing the acid out put in terms of body weight. 3. Pentagastrin stimulates a dose‐dependent increase in acid secretion in the range 0.5‐32 microgram kg‐1 hr‐1 when the response to each dose is assayed on separate occasions. Pentagastrin 64 microgram kg‐1 hr‐1 does not produce a further increase in acid secretion. The acid response to pentagastrin 1‐16 microgram kg‐1 hr‐1 assayed on a single occasion by a continuous infusion method shows a dose‐response relationship up to 8 microgram kg‐1 hr‐1 when it reaches a plateau of secretion. There is no difference between the two methods of assaying the gastric acid stimulating activity using doses of pentagastrin up to 8 microgram kg‐1 hr‐1. 4 The acid secretion in response to pentagastrin 8 microgram kg‐1 hr‐1 reaches a maximum after 45 min of stimulation and thereafter shows tachyphylaxis. Over a period of 5 hr there are at least two phases of tachyphylaxis distinguishable. During the period 0.75‐‐2.5 hr of stimulation there is a fast phase of tachyphylaxis (‐32.0 muequivH+kg‐1 15 min‐1). This is followed by a slow phase of tachyphylaxis (‐9.4 muequivH+kg‐1 15 min‐1) up to 5 hr of stimulation. 5. The absolute rate of the fast phase of tachyphylaxis of acid secretion (muequivH+kg‐1 15 min‐1) increases with increasing doses of pentagastrin, but rates of tachyphylaxis are similar when expressed as a percentage of the peak acid response to the particular dose of pentagastrin (5.1‐‐7.8% 15 min‐1). Synthetic human gastrin‐17, the synthetic C‐terminal decapeptide of human gastrin and the C‐terminal tetrapeptide of gastrin have comparable rates of tachyphylaxis. The possible receptor models for the tachyphylaxis of gastrin‐stimulated acid secretion are discussed.
Evidence for H2‐receptor‐mediated feed‐back regulation of histamine release from endocrine cells in the rat stomach.
Authors: Håkanson R , Larsson L I , Liedberg G , Sundler F
Published: December 2014

1. Pentagastrin reduces the concentration of gastric mucosal histamine in the rat. This effect is counteracted by large doses of histamine H2‐receptor agonists which are particularly effective if infused I.V. 2. After blockade of histamine H2‐receptors but not of H1‐receptors, the pentagastrin‐induced reduction of mucosal histamine is greatly augmented and H2‐receptor agonists no longer inhibit the response to pentagastrin. 3. It is suggested that in the rat stomach, H2‐receptors occur on the histamine storing endocrine cells as well as on parietal cells and that mobilized mucosal histamine inhibits further release of histamine by way of H2‐receptor‐mediated auto feed‐back.
Glutamate sensitivity and distribution of receptors along normal and denervated locust muscle fibres.
Authors: Cull-Candy S G
Published: December 2014

1. Factors influencing the glutamate sensitivity of extrajunctional regions of innervated and denervated locust muscle fibres have been investigated. Properties of the two types of extrajunctional glutamate receptors, D‐ and H‐receptors, have been studied in regions of high and low sensitivity. 2. The low level of extrajunctional sensitivity which is normally present in innervated fibres was 20‐30 times higher at the muscle‐tendon junction than at other sites; increased sensitivity extended about 20‐40 micron from the tendon. After denervation or localized damage the entire extrajunctional sensitivity was increased approximately 100 times above control levels. 3. Applying L‐glutamate (which activates D‐ and H‐receptors) and DL‐ibotenate (which activates H‐receptors) from multibarrelled micropipettes showed that increased extrajunctional sensitivity resulted from an increase in D‐receptors while H‐receptors were apparently unchanged. 4. Coulomb dose vs. response relationships for the action of glutamate on D‐receptors were similar when obtained at the muscle‐tendon junction and nerve‐muscle junction of innervated fibres or at extrajunctional regions in denervated fibres. 5. Time course of onset and percentage desensitization of D‐ and H‐receptors in innervated fibres were similar. The percentage desensitization of D‐receptors in extrajunctional regions of high sensitivity was greatly reduced. 6. It is suggested that D‐ and H‐receptors are independent and that the trigger for increased receptor sensitivity acts specifically on D‐receptors. In all respects so far studied, the D‐receptors resemble extrajunctional ACh‐receptors in vertebrate muscle.
Effects of membrane potential and temperature on the excitatory post‐synaptic current in the crayfish muscle.
Authors: Onodera K , Takeuchi A
Published: December 2014

1. Effects of membrane potential and temperature on the excitatory post‐synaptic current (e.p.s.c.) were studied in the voltage‐clamped crayfish muscle. E.p.c. was recorded either by measuring the feedback current through an intracellular wire electrode or by focal recording with an extracellular micro‐electrode. 2. The amplitude of the e.p.s.c. obtained by the voltage clamp method varied almost linearly with membrane potential between ‐100 mV and +70 mV, whilst the reversal potential was +23.8 +/‐ 3.9 mV (S.E. of mean). 3. The declining phase of the extracellular e.p.s.c. was slightly prolonged by depolarization and shortened by hyperpolarization. Potential dependence of the decay time constant was expressed by tau = a exp (AV), with a = 2.78 msec and A = 0.0037 mV‐1. 4. The decay time constant had a Q10 of 2.3 and the growth time had a Q10 of 1.5. 5. The voltage dependence of the decay phase of the e.p.s. was the reverse of that found in frog end‐plate. It is concluded that the voltage dependence of the time course is not related either to the charge of ions which carry the synaptic current or to the charge of the transmitter.
Effects of dithiothreitol on end‐plate currents.
Authors: Terrar D A
Published: December 2014

1. End‐plate currents have been studied in frog cutaneus pectoris nerve‐muscle preparations mounted in continuously flowing solution, using the voltage clamp technique. 2. Exposure of the muscle to 1 mM‐dithiothreitol reduced the amplitude of end‐plate currents by a factor of 2.7 (mean; range 1.6‐3.4; twelve fibres). 3. 1 mM‐dithiothreitol also caused a 2.7‐fold (2.3‐3.1) increase in the rate of decay, and a 1.4‐fold (1.3‐1.6) decrease in the time to peak of end‐plate currents. During the onset of action of dithiothreitol, there was little or no indication of departure of end‐plate current decay from a simple exponential. 4. Dithiothreitol actions on amplitude and decay of end‐plate currents developed with similar time courses and both effects were slower in onset at pH 7.2 than at pH 8.5. 5. The actions of dithiothreitol were reversed by exposure of the muscle to 1 mM‐5,5'‐dithio‐bis‐(2‐nitrobenzoic acid). 6. Following dithiothreitol treatment, the rates of decay of end‐plate currents continued to depend on membrane potential; there was little or no change in the slope of the relation between in (rate of decay) and membrane potential, consistent with little or no change in the dipole moment of a gating molecule for ion channels. 7. Dithiothreitol changed the relation between peak end‐plate current and membrane potential, so that peak conductance increased at more negative membrane potentials; this finding could be accounted for in terms of the closure of ion‐channel gates becoming faster though remaining voltage‐sensitive after exposure to dithiothreitol. 8. It is concluded that dithiothreitol causes changes in the kinetics of gating of ion channels associated with receptors and that these changes accompany changes in the binding of ACh to receptors.
Anion transport of the red cell under non‐equilibrium conditions.
Authors: Ormos G , Mányai S
Published: December 2014

1. The exchange of sulphate for chloride across the human red cell membrane was measured in both directions, i.e. by sulphate influx and sulphate efflux. The influence of the concomitant transient pH changes was minimized by phosphate buffer and by choosing experimental conditions of moderate pH sensitivity (pH 6.4 and 7.8). Sulphate self exchange was determined in chloride‐free erythrocyte suspensions. 2. The transport of external sulphate into red cells proceeded at a 15‐fold greater rate if its initial concentration was raised from 5 to 95 mM. In contrast the velocity constant of sulphate efflux into sodium chloride medium increased only twofold when the intracellular sulphate concentration was increased. To explain this asymmetry it is proposed that external sulphate ions are more able to complete with chloride for the anion transport sites that those present in the cell interior. 3. The transient membrane potential due to the uneven distribution of sulphate and chloride was shown by the rapid introduction of chromate into the cells. When the erythrocytes contained chloride and the external anion was sulphate, the cells took up chromate 50 times (16.5 degrees C) faster than with equilibrium chloride distribution. 4. Chloride efflux into sodium sulphate media was measured by a chloride‐sensitive electrode. Under buffered conditions in neutral and alkaline media two kinetic components were observed as the result of chloride exchange against hydroxyl and sulphate ions. At pH 6.4, chloride efflux was characterized by a single velocity constant identical to that of sulphate movement in the opposite direction. The results show that under appropriate circumstances net chloride efflux measurements can provide comparative data on the anion permeability of the red cell membrane.
Thermal stimulation of intra‐abdominal veins in conscious rabbits.
Authors: Cranston W I , Hellon R F , Townsend Y
Published: December 2014

1. Infusions of hot and cold Hartmann's solution were given into the hepatic portal vein and inferior vena cava of conscious rabbits. Similar infusions were given into an ear vein as controls. The time integral of the displacement of brain temperature was measured. 2. There was no evidence for the presence of warm sensors in the inferior vena cava, portal vein, liver or hepatic vein, and no evidence for a concentration of cold sensors in the inferior vena cava. 3. There may be cold‐sensitive elements in the portal vein or the tissue perfused by blood passing through it.
The effect of acute and chronic hypoxia on thoracic gas volume in anaesthetized rats.
Authors: Barer G R , Herget J , Sloan P J , Suggett A J
Published: December 2014

1. Thoracic gas volume at end expiration (functional residual capacity, FRC) was measured in chronically and acutely hypoxic anaesthetized rats by a plethysmograph method. 2. FRC, measured during air breathing, was 34‐62% larger in rats which had been kept in an environmental chamber in 8, 10 or 12% O2 for 3 weeks than in littermate controls. FRC returned to normal after the rats had returned to air for 9 days. There was no constant difference in the pattern of breathing between control and chronically hypoxic rats. 3. Pressure‐volume curves measured post mortem showed no difference in the volume of the lung at 25 cm H2O pressure or in the compliance of the lung between chronically hypoxic and control rats. Thus there was no gross mechanical change in the lung to account for the increase in FRC. 4. Acute hypoxia caused by breathing 12% O2 increased FRC in control but not in chronically hypoxic rats. The increase in FRC in control rats was abolished by combined blockade of the vagus nerves and carotid bodies (with procaine) but not by vagal blockade alone. 5. The combined vagal and carotid body blockade reduced FRC significantly in rats which had been in 10% O2 for 3 days but not in those which had been in 10% O2 for 21 days. 6. Lung area measured from radiographs was not reduced by a muscle relaxant in chronically hypoxic rats. Electromyograms from anterior intercostal muscles and the diaphragm showed no electrical activity in expiration in chronically hypoxic rats which might indicate an active muscular basis for their increased FRC. However when FRC was raised by acute hypoxia in control animals there was also no increase in electrical activity in expiration which could have explained their increase in lung volume. 7. We concluded that the increase in FRC during acute hypoxia in control rats was probably due to a reflex from the carotid body. The increase in FRC in chronically hypoxic rats, which was present while they breathed air, may have had an active muscular component in the early stages but later on there was possibly a structural factor in the chest wall.
Ionic currents in mammalian fast skeletal muscle.
Authors: Duval A , Léoty C
Published: December 2014

1. The double sucrose‐gap technique has been applied to rat skeletal muscle fibres to study the ionic currents under voltage‐clamp conditions. 2. The iliacus muscle was found to be of 'fast' type according to the characteristics of the twitch generated by an action potential. 3. Micro‐electrode measurements have shown that the intracellular potential is under good control even when an inward current develops. 4. The components of an equivalent circuit with two time constants have been estimated from the records of the capacitive current. 5. In rat muscle, between 15 and 21 degrees C, inward and outward currents are similar to sodium and potassium currents found in frog muscle at lower temperature (1‐‐3 degrees C). 6. The inward current which depends on [Na]o and is abolished by tetrodotoxin is carried by sodium ions. Related to the mean value for the holding potential (‐90.5 mV) this current reaches its maximum amplitude a +40 and +50 mV, reverses between +130 and +150 mV and its half inactivation occurs between +14 and +22 mV. The effect of low doses of tetrodotoxin suggests that two components participate in the sodium current. 7. The delayed outward current which shows inactivation is divided in two components: (i) the fast has a linear instantaneous current‐voltage relation and differs from the fast component of frog muscle in that its equilibrium potential is more negative than the resting potential; (ii) the slow has a linear instantaneous current‐voltage relation and the mean value for its equilibrium potential is 26 mV less negative than the resting potential. 8. Inward‐going rectification is present in rat muscle.
Endogenous prostaglandins and gastric secretion in the cat.
Authors: Baker R , Jaffe B M , Reed J D , Shaw B , Venables C W
Published: December 2014

1. The gastric juice outputs of acid, pepsin, PGE and PGF, and the plasma concentrations of PGE and PGF have been measured in response to I.V. infusions of pentagastrin, histamine and insulin in the conscious cat. 2. There were significant correlations between the output of gastric acid and gastric outputs of both PGE and PGF during secretion produced by all stimulants. Furthermore, there were similar significant correlations between the gastric outputs of pepsin and both PGE and PGF. However, during insulin stimulation there was significantly more pepsin output per unit PGE or PGF output than during either pentagastrin or histamine stimulation. 3. The correlations between the outputs of gastric acid and both PGE and PGF were similar during pentagastrin and insulin stimulation whereas those between acid and PGE and PGF altered during the infusion of histamine. 4. It is concluded that these data partially, but not entirely, support the hypothesis that local release of prostaglandins may act as a negative feed‐back mechanism on gastric acid secretion. 5. Plasma prostaglandin concentration did not correlate with changes in acid or pepsin secretion.
Quelling of spontaneous transmitter release by nerve impulses in low extracellular calcium solutions.
Authors: Erulkar S D , Rahamimoff R , Rotshenker S
Published: December 2014

1. The effect of nerve stimulation on spontaneous transmitter release was studied at the frog neuromuscular synapse which was bathed in a solution containing very low extracellular calcium concentration. Conventional methods for intracellular and extracellular recording were used and the pattern of quantal liberation following the nerve stimulus was determined. 2. Stimulation of the motor nerve (at rates between 0.09 and 2Hz) caused a reduction in the frequency of the miniature e.p.p.s in comparison to the prestimulation values. 3. The mean distribution of the time of occurrence of the miniature e.p.p.s during the interstimulus period showed periodic oscillations. 4. The quelling effect of nerve stimulation on transmitter release is explained by the hypothesis that a low [Ca]o a reversed electrochemical gradient for calcium occurs and nerve stimulation causes an increased calcium conductance leading to calcium efflux which in turn temporarily reduces [Ca]i and transmitter release.
The pattern of stimulated breathing in man during non‐elastic expiratory loading.
Authors: Garrard C S , Lane D J
Published: December 2014

1. The pattern of breathing expressed as the relationship between tidal volume and the components of breath interval was studied in normal subjects during CO2 rebreathing, both under unloaded conditions and following the introduction of a non‐elastic expiratory resistance. 2. Under unloaded conditions end‐expiratory thoracic gas volume (FRC) measured plethysmographically did not alter during the course of the rebreathing experiment. Maximum tidal volume attained (VT, max.) was equal to or just less than the inspiratory capacity of the subject measured at rest. Expiratory reserve volume was not encroached upon even at the highest levels of ventilation. 3. Under loaded conditions the pattern of breathing was altered. VT, max. was diminished in all subjects and FRC showed a progressive rise during rebreathing which was proportional to the resistive load afforded by the artificial resistance. There were no consistent differences in the components of breath duration either at rest or on maximal ventilatory stimulation between the loaded and unloaded states. 4. It is suggested that the pattern of breathing adopted under conditions of expiratory non‐elastic loading is influenced more by the secondary effects of breathing at an elevated lung volume, than by the effect of the non‐elastic load per se.
Light‐activated hydrolysis of GTP and cyclic GMP in the rod outer segments.
Authors: Bignetti E , Cavaggioni A , Sorbi R T
Published: December 2014

1. The hydrolysis of guanosine triphosphate (GTP) and the consequent formation of guanosine diphosphate (GDP) and phosphate (P1) are activated by light in a suspension of broken retinal rods: the hydrolysis rate with GTP in the micrometer concentration range is 2.5‐3.5 n‐mole/min per mg of rhodopsin in the preparation. 2. The ionic composition of the medium suspending the rods is not critical: the hydrolysis is present in NaCl saline solution with MG2+ as well as in Tris‐HC1 buffer solution, and with the chelating agent EDTA. 3. The ionic strength is critical: the effect is reduced when the broken rods are suspended in a low salt mannitol solution, and is altogether abolished when they are separated from the mannitol solution; it reappears when the mannitol solution is added again in the presence of salts. An element essential for the effect is thus reversibly released in the mannitol solution. No hydrolytic activity on GTP, however, is found in the mannitol soluble fraction. 4. The cyclic nucleotide phosphodiesterase is eluted from the rods in the mannitol solution, and is reaggregated to the rods in the presence of salts; once recombined with the rods, it can be activated by light. 5. The activation of the phosphodiesterase by light is present in the absence of added nucleotide triphosphates.
The febrile responses in rabbits and rats to leucocyte pyrogens of different species.
Authors: Borsook D , Laburn H , Mitchell D
Published: December 2014

1. We have investigated the effects on body temperature of rats and rabbits of leucocyte pyrogen derived from the blood of rat, rabbit, ox, pig and baboon. 2. In the rabbit intravenous injections (3.5 ml.) of solutions containing leucocyte pyrogen derived from ox, pig and rabbit blood produced fevers with short latencies; no fevers resulted from injections of similar solutions derived from rat or baboon blood. 3. In the rat intraperitoneal injections (2.0 ml.) of solutions containing leucocyte pyrogen derived from ox blood caused a fever, while pig leucocyte pyrogen produced a marked hypothermia. Neither rabbit, baboon, nor rat leucocyte pyrogen had any significant effect on rectal temperature of the rats. 4. Our results show that there is a variability of response in the rat and the rabbit to injection of leucocyte pyrogen of different species; leucocyte pyrogen may be species specific.
Effects of vasoactive intestinal polypeptide on intestinal absorption and blood flow.
Authors: Mailman D
Published: December 2014

1. Intestinal absorption and blood flow in anaesthetized dogs was determined after I.V. infusion of vasoactive intestinal polypeptide (VIP) (1.75‐175 ng/min) to determine the contribution of the cardiovascular changes to transport. 2. 22Na and 3H2O were utilized to determine the unidirectional fluxes of Na and H2O from saline perfused through the ileal lumen and the clearances of 3H2O were used to determine total and absorptive site blood flow. 3. Net Na and H2O absorption were reversed to secretion by VIP at 175 ng/min due to a significant decrease in unidirectional absorptive fluxes and smaller increases in secretory fluxes. 4. Arterial pressure and absorptive site blood flow were reduced in proportion to the changes in Na and H2O fluxes. 5. Total and absorptive site blood flow decreased and the blood flow resistances increased. 6. Prior treatment with guanethidine to suppress sympathetic effects did not greatly affect the responses to VIP. Prior treatment with atropine to suppress cholinergic effects inhibited most of the effects of VIP. 7. Absorptive site blood flow was linearly related to absorptive fluxes of Na and H2O but with different slopes for results from atropinized dogs as compared to those from dogs given VIP alone or VIP plus guanethidine. 8. It was concluded that VIP reduces gut absorption through a generalized cardiovascular effect and also through a mechanism which depends on the release of ACh by the gut.
Antidipsogenic effect of intracranial injections of substance P in rats.
Authors: De Caro G , Massi M , Micossi L G
Published: December 2014

1. The effect on water intake of intracranial injections of Substance P was studied in the rat. 2. Substance P strongly inhibited drinking elicited by Angiotensin II, Carbachol water deprivation or sodium chloride load, in that order. 3. The peptide was particularly effective when water intake was induced by injections of Angiotensin II into the preoptic area. In these experiments, drinking was inhibited by doses of Substance P as low as 1 ng. 4. The results suggest that in the rat Substance P may play a role in the brain in the regulation of water intake, acting as a thirst inhibitor.
Control of calcium channels by membrane receptors in the rat parotid gland.
Authors: Marier S H , Putney J W , Van de Walle C M
Published: December 2014

1. The mechanism of action of agonists that stimulate K release from the parotid gland was investigated by monitoring efflux of 86Rb from rat parotid slices. 2. As in previous studies, the 86Rb release was increased by agonists in a biphasic manner. An early, transient phase occurred that was independent of extracellular Ca. This was followed by a sustained (or slowly falling phase) that required extracellular Ca. 3. The agonists were investigated as to their additivity and to their sensitivity to inhibition by a number of putative Ca‐antagonists. 4. When carbachol, epinephrine and Substance P were employed in supramaximal concentrations, no combination of agonists produced a summated 86Rb release response, despite the fact that the Ca concentration was submaximal. 5. The sustained phase of 86Rb release, which is dependent on extracellular Ca, was blocked by La, Ni, Co and neomycin; the transient phase was unaffected by these agents. 6. The local anaesthetics tetracaine and procaine inhibited both the transient and sustained phases of the responses to carbachol and phenylephrine; responses to Substance P and to the divalent cationophore, A23187, were largely refractory to this effect. 7. These results support the contention that, in the parotid, muscarinic, alpha‐adrenergic and peptide receptors regulate the same Ca influx sites. 8. Also, these results suggest that La, Ni, Co and neomycin appear to antagonize the action of Ca by impeding inward movement of the cation through activated Ca influx sites. 9. Finally, the local anesthetics appear to inhibit, and therefore, serve to define, a transduction step between receptor occupation and channel activation. 10. In the case of the Substance P mechanism, it appears that the transduction mechanism must be qualitatively different to that for the muscarinic or alpha‐adrenergic mechanisms.
Sensitization and habituation of dorsal horn cells in cats.
Authors: Egger M D
Published: December 2014

1. Extracellular recordings were obtained from spinal dorsal horn cells in acutely spinalized cats anaesthetized with sodium pentobarbitone. The dorsal horn cells studied responded to ipsilateral tactile stimulation of the central pad of the hind foot. Eleven short latency dorsal horn cells driven by electrical stimulation of the foot pad were studied intensively; these short latency dorsal horn cells all discharged within 1.5 msec of the arrival of an afferent volley at the dorsal root entry zone. Electrode tip sites were histologically verified to lie near the medial border of the dorsal horn in the seventh lumbar segment, in Rexed's laminae III and IV. 2. Electrical stimulation of the foot pad not only activated the dorsal horn cells studied, but also produced a reflex discharge which was monitored by recording from the ipsilateral first sacral ventral root, which had been sectioned intradurally and mounted on bipolar recording electrodes. Repeated stimulation of the foot pad at moderate intensities and frequencies (e.g. three times threshold for the ventral root response at 5 Hz) typically produced a transitory increase in the magnitude of the reflex discharge (sensitization) followed by a marked waning of the reflex magnitude (habituation). Within a few minutes following cessation of stimulation, the reflex magnitude returned to its prestimulation value. During repeated bouts of five hundred stimuli each, at frequencies from 1.0 to 10.0 Hz, and intensities 1.5‐10.0 times reflex threshold, the firing pattern of a short latency dorsal horn cell was monitored along with the magnitude of the ventral root response. Changes in response patterns of the dorsal horn cells were compared to those of the reflex discharges. 3. The short latency dorsal horn cells fell into two distinct patterns of response. The firing pattern of six dorsal horn cells paralleled the response pattern of the reflex discharge; when the reflex increased in magnitude, each of these dorsal horn cells increased in number of responses per stimulus; when the reflex discharge decreased in magnitude, each of these dorsal horn cells decreased the number of responses per stimulus. These dorsal horn cells were characterized by the following: intermediate thresholds to tactile stimulation, comparable to that of the reflex discharge itself; relatively low numbers of responses per stimulus (mean: 1.3/stimulus); low spontaneous activity rates (once per 10 sec or less). 4. The firing patterns of the other class of short latency dorsal horn cells did not parallel the response pattern of the reflex discharge; these showed only a rather rapid, though moderate, decrease in responses per stimulus over the entire range of intensities and frequencies tested. These five dorsal horn cells were characterized by the following: thresholds of tactile stimulation considerably below that of the reflex discharge itself; bursts of responses following each stimulation (mean: 7...
The physiological properties of amine‐containing neurones in the lobster nervous system.
Authors: Konishi S , Kravitz E A
Published: December 2014

1. Our previous studies have shown that octopamine and serotonin are found associated with a system of neurones in the connective tissue sheath of the second roots of lobster thoracic ganglia. To try to understand the mechanism of activation of these neurones, we undertook an examination of their general physiological properties. 2. All of the neurones receive excitatory synaptic input that has a cholinergic pharmacology, which suggests that it may be from sensory neurones. A very limited number of cells, possibly one, provdes the total synaptic input to all the cells in the roots of the second and third thoracic segments. 3. The cells within one root are electronically coupled to each other. The extent of coupling varies widely between cells; on occasion the coupling is sufficiently tight for action potentials originating in one cell to trigger action potentials in the neighbouring cell. 4. The majority of the cells show no spontaneous activity at temperatures below 14 degrees C, but become spontaneously active above that temperature. Cells cycle reversibly from silent to continuously active to bursting and back as the temperature is increased and decreased. 5. Octopamine and serotonin both inhibit the bursting activity. The octopamine response is blocked by phentolamine but not by propranolol, while the inhibitory action of serotonin is unaffected by either of these drugs. The amine‐inhibition of the firing could be an autoregulatory mechanism for cell activity. 6. The physiological properties described in this paper suggest that the widely dispersed amine‐containing neurones in lobsters behave like a neurosecretory organ in terms of their mechanism of activation.
Properties of intraoral mechanoreceptors represented in the mesencephalic nucleus of the fifth nerve in the cat.
Authors: Linden R W
Published: December 2014

1. The activity of neurones in the mesencephalic nucleus of the fifth nerve that respond to forces applied to the teeth were recorded using extracellular microelectrodes; the properties of these neurones have been studied. 2. Electrophysiological evidence consistent with the view that primary afferent intraoral mechanoreceptor fibres have their cell bodies in the trigeminal mesencephalic nucleus is presented. 3. Two groups of intraoral mechanoreceptor neurones were found. The first group, the periodontal mechanoreceptor neurones, which have been described by previous workers, responded to electrical stimulation of the ipsilateral superior or inferior dental nerves and to forces applied to single teeth in the ipsilateral maxilla or mandible respectively. The response characteristics of the mesencephalic periodontal mechanoreceptor neurones differed in two respects from those observed in peripheral nerve studies by previous workers: (a) there were no spontaneously active neurones, and (b) there were no neurones that responded for over 10 sec to a sustained application of a suprathreshold mechanical stimulus to the teeth. The second group, not described before, responded to electrical stimulation of the ipsilateral palatine nerve, and responded to forces applied to all the teeth in the maxillary arch, both contralateral and ipsilateral as well as to forces applied to the nose and hard palate. The site of these receptors is unknown. They have been termed 'Type P' intraoral mechanoreceptors. 4. The recording sites of both the periodontal and Type P mechanoreceptor neurones were all situated in the caudal part of the mesencephalic nucleus of the fifth nerve.
Inhibitory action of dopamine on cat carotid chemoreceptors.
Authors: Docherty R J , McQueen D S
Published: December 2014

1. The influence of some drugs which affect the dopaminergic system was studied on chemosensory responses to dopamine (DA), acetylcholine (ACh), sodium cyanide NaCN) and hypoxia during experiments on pentobarbitone anaesthetized cats in which chemoreceptor activity was recorded from the peripheral end of a sectioned sinus nerve. 2. Spontaneous chemosensory activity was inhibited in a dose‐dependent manner by DA (0.5‐5 microgram, I.A.). Higher doses (10‐50 microgram) caused a delayed increase in discharge and were associated with inconsistent inhibitory responses. 3. The DA antagonist alpha‐flupenthixol (0.2 mg/kg, I.A.) blocked the inhibitory response to DA without affecting either the spontaneous discharge frequency or the response to ACh. The effect of NaCN was potentiated, and during hypoxia chemoreceptor activity increased more rapidly, although the maximum frequency attained was not appreciably different from control values. Similar results were obtained with haloperidol (0.5 and 1.0 mg/kg, I.V.). 4. Higher doses of alpha‐flupenthixol (0.5‐1.0 mg/kg, I.A.) increased spontaneous chemoreceptor activity, but this was regarded as a non‐specific effect of the drug since at these doses the inhibitory effect of 5‐hydroxytryptamine (5‐HT) was also abolished. 5. The animals were exposed to alternate periods of hypoxia and hyperoxia following administration of the tyrosine hydroxylase inhibitor alpha‐methyl p‐tyrosine (AMPT, 0.2‐10 mg/kg, I.A.). The inhibitory response previously evoked by amphetamine was abolished, and electron microscopic studies showed a great reduction in the number of dense‐cored granules, both of which suggested that DA levels in the carotid body had been substantially reduced. Responses to NaCN and hypoxia were slightly potentiated following AMPT, but neither spontaneous activity nor the response to ACh was affected. 6. Apomorphine (0.05‐0.2 mg/kg, I.A.) inhibited the chemoreceptor discharge for up to 45 min, an effect which was antagonized by alpha‐flupenthixol (0.2 mg/kg, I.A.), implying it resulted from DA receptor stimulation. Although responses to NaCN, hypoxia and higher doses of ACh were reduced following administration of apomorphine, the reduction was not very marked. 7. These results are not compatible with the theory of Osborne & Butler (1975), that in normoxia DA is tonically released in the carotid body and suppresses spontaneous chemosensory activity. 8. It is concluded that DA modulates chemosensory activity by influencing the rate of increase in discharge, without affecting maximum discharge frequency. The mechanism whereby DA is released in response to increased chemosensory activity remains to be established.
Effects of internal free calcium upon the sodium and calcium channels in the tunicate egg analysed by the internal perfusion technique.
Authors: Takahashi K , Yoshii M
Published: December 2014

1. The unfertilized egg of the tunicate, Halocynthia roretzi, was intracellularly perfused with various solutions. 2. The perfusion apparatus consisted of lower and upper compartments which were connected by a small glass funnel. A denuded egg cell without chorion was dropped into the funnel and brought into close contact with the glass wall of the funnel. The membrane of the egg faced to the lower compartment was ruptured by a slight difference of hydrostatic pressure and the inside of the egg was perfused with the internal solution flowing through the lower compartment. The current across the upper membrane was analysed by voltage‐clamp technique. 3. The egg cell in contact with 400 mM‐Na external solution and perfused intracellularly with 400 mM‐Na for 30 min showed a relatively low Na reversal potential, +6 mV, in comparison with +60 mV in the intact egg in standard artificial sea water. The exchange efficiency was monitored by observing the shift of Na reversal potential during perfusion with high Na internal perfusate. 4. The internal perfusate containing F‐ ions stabilized the egg membrane and kept the excitability for 1‐‐2 hr during the intracellular perfusion. With the internal F‐ perfusate the intracellular cationic content was changed to 400 mM‐Na, K, Rb or Cs (external solution of 400 mM‐Na) and permeability ratios of the egg Na channel were estimated as PNa:PK:PRb:PCs=1.0:0.14:0.05:0.04. The internal F‐ perfusate abolished Ca current which was consistently observed in the intact egg, while the internal Cl‐ perfusate kept both Na and Ca current as in the intact egg. However with the internal Cl‐ perfusate the egg cell could not be kept in good condition more than 20‐30 min. 6. The effects of intracellular free Ca ions upon the egg Na and Ca channels were analysed by using Ca ion‐buffered internal Cl‐ and high Na perfusate. The results showed that internal Ca ions above 10(‐6) reduced the Ca current and enhanced the Na current at the same time. In the range between 10(‐5) and 10(‐4) M the Ca current became half of the control obtained with zero free Ca perfusate while the Na conductance at the zero current level doubled. The internal Ca ions above one mM seemed to abolish the Ca current and to reduce the Na current as well. The reciprocal effect of intracellular Ca ions upon the egg Na and Ca channels was demonstrated in the concentration range from 10(‐6) to 10(‐3) M.
Evoked depolarizing and hyperpolarizing potentials in reticulospinal axons of lamprey.
Authors: Matthews G , Wickelgren W O
Published: December 2014

1. Intracellular recordings were made from reticulospinal axons (Müller axons) in the lamprey spinal cord. Electrical stimuli applied to the spinal cord surface elicited depolarizing and hyperpolarizing 'synaptic‐like' potentials in Müller axons. The physiological basis of these evoked potentials was investigated. 2. The depolarizing response was not the result of increased extracellular K, as demonstrated by the constancy of the undershoot of the axonal action potential during the depolarization, by the failure of the response to summate during repetitive stimulation and by the failure of the response amplitude to vary as predicted when the [K] of the saline was varied. 3. When the membrane potential of the axon was varied by passing current through a micro‐electrode, the amplitude of the depolarizing evoked potential decreased at membrane potentials positive to the resting potential and increased up to a maximum when the axon was hyperpolarized by about 10 mV. The extrapolated 'reversal potential' for the depolarizing response was about 15 mV positive to the normal ‐80 mV resting potential of the axon. However, the amplitude of the response did not continue to grow with hyperpolarizations greater than 10 mV, and, thus, the response did not behave as would a normal depolarizing synaptic potential. 4. Müller axons make numerous electrical synapses with spinal motoneurones and interneurones, and this suggested that the depolarizing response might be a coupling potential. In agreement with this idea, quantitative correspondence was found between changes in the input resistance of the axon produced by the depolarizing response and the variation in the depolarizing response amplitude. Thus, although the depolarizing response mimicked in some ways the behaviour of an excitatory synaptic potential, we conclude that it is a coupling potential. 5. The hyperpolarizing response also appeared to be a coupling potential. Its amplitude was not changed by hyperpolarizing the axon up to 30 mV and was decreased by depolarizing the axon sufficiently to decrease the axon's input resistance. 6. It is proposed that both depolarizing and hyperpolarizing evoked potentials in lamprey Müller axons are a result of passive flow of current from cells activated by the spinal cord stimulus and electrically coupled to Müller axons.
Water response of the frog olfactory epithelium as observed from the olfactory bulb.
Authors: Arito H , Iino M , Takagi S F
Published: December 2014

The water response elicited by application of distilled water on the olfactory epithelium was recorded extracellularly from single olfactory bulb neurones. Characteristics of the water response in the frog olfactory epithelium were examined in comparison with those of the water response in the gustatory and palatal organs. 1. Effects of various electrolyte solutions on the generation of the water response were studied by dripping distilled water on the olfactory epithelium after adaptation to each of these electrolyte solutions. Number of the olfactory bulb cells responding to distilled water increased with increasing the charge of the adapting cations and also with decreasing the size of the cations with a few exceptions. 2. Magnitude of the 'water response' increased with decreasing concentration of salt in the solution which was dripped after adaptation to the isotonic solution of the same salt. 3. The water response was effectively depressed by an electrolyte solution but not by a non‐electrolyte solution. An electrolyte also depressed effectively the water response which was produced after adaptation to an organic salt solution. 4. The water response was blocked by treatment of the olfactory epithelium with the uranyl ions which had high affinity for phospholipids. A tentative hypothesis on the generating mechanism of the water response in the frog olfactory epithelium is presented on the basis of the present experimental results and the water responses of the gustatory and palatal organs so far reported.
Albumin permeability of the peritubular capillaries in rat renal cortex.
Authors: Bell D R , Pinter G G , Wilson P D
Published: December 2014

1. Two series of experiments were carried out to determine the permeability of the renal cortical peritubular capillaries to albumin under control conditions in the concentrating kidney and after an infusion of hypo‐osmotic fluid amounting to 6% body weight. 2. In the first series of these experiments the turnover of the interstitial albumin pool of the renal cortex was studied. Specifically, the mean transit time of albumin molecules from arterial plasma to renal lymph was measured in nine rats of each group. Mean values of 39.0 +/‐ 2.8 and 30.6 +/‐ 2.2 (S.E. of mean) min were found for the control and infused groups, respectively. 3. In the second series of experiments the interstitial distribution volume of plasma albumin in renal cortex was determined in twenty‐three control and twenty‐two infused rats. Mean values of the extravascular distribution volumes were 1.66 +/‐ 0.21 and 1.37 +/‐ 0.18 (S.E. of mean) microliter/100 mg tissue, respectively. 4. The unidirectional clearance of albumin from the capillary to the interstitium in the control and infused groups, respectively, was calculated to be 7.1 +/‐ 1.0 and 7.5 +/‐ 0.9 (S.E. of mean) ml. sec‐1 10(‐4) in 100 g cortical tissue. 5. For the reabsorbing surface of the peritubular capillaries in the renal cortex, a lower bound was calculated for sigma, the reflexion coefficient of albumin. The reflexion coefficient was found to be higher than 0.998 under both experimental conditions.
Adenosine‐induced release of cyclic adenosine 3',5'‐monophosphate from the left ventricle in the anaesthetized intact dog.
Authors: Huynh-Thu T , Lammerant J
Published: December 2014

1. The influence of adenosine on the release of cyclic adenosine 3',5'‐monophosphate (cyclic AMP) from the heart was examined in twenty‐two anaesthetized intact dogs. The animals were pre‐treated with propranolol and vagotomized. The rate of nucleotide release from the left ventricle was determined as the product of the left ventricular myocardial plasma flow and the coronary veno‐arterial difference in plasma nucleotide concentration. 2. Adenosine was infused into the left ventricle during three successive 15 min periods at rates of 25, 50 and 100 n‐mole/kg. min, respectively. The mean blood pressure in the ascending aorta was prevented from falling by inflating a balloon placed into the thoracic aorta. The measurements were performed before the infusion and at the 10th min of each infusion period. The values given are means +/‐ S.E. 3. During the 45 min infusion of adenosine at increasing rate, the cyclic AMP concentration in arterial plasma increased from 7.0 +/‐ 0.3 to 14.0 +/‐ 0.9 p‐mole/ml. The nucleotide was released from the left ventricle at rates increasing from 48.2 +/‐ 7.1 to 206.5 +/‐ 56.2 p‐mole/100 g. min while the left ventricular myocardial blood flow increased from 127 +/‐ 6 to 399 +/‐ 33 ml./100 g.min. The oxygen consumption of the left ventricle was not modified. 4. When adenosine was infused at a rate of 100 n‐mol/kg.min, the thorax was opened and the apex of the heart and the left atrial appendage were removed for nucleotide assay. The cardiac cyclic AMP concentration did not differ from that observed in control dogs. 5. The results suggest that cyclic AMP is likely to be involved in the membrane and cellular events underlying the relaxant effect of adenosine on the coronary smooth muscle. The lack of change in cardiac cyclic AMP concentration, as determined by whole tissue extractions, is consistent with a study by others showing that, under normoxic conditions, cyclic AMP is released from a small, compartmentalized fraction of the cyclic AMP content of the heart. The elevation of the plasma nucleotide concentration could result from adenosine effects on various cell systems or organs, in addition to the observed release from the heart.
Volume changes in cells of the outer medulla during perfusion of the rat kidney.
Authors: Bullivant M
Published: December 2014

1. A method is described for the perfusion of the rat kidney with a medium resembling rat plasma in its ionic constituents but with 3% polyvinylpyrrolidone (mol.wt. 44,000) replacing the plasma proteins. 2. In the early stages of perfusion, there was rapid swelling of the tubular cells in the outer medulla, a low glomerular filtration rate and a low filtration fraction. 3. After 30 min perfusion, the tubular cell volume in the outer medulla was normal and filtration had increased and stabilised. 4. Cell swelling and the low initial filtration fraction were prevented by (a) adding 50 mM‐mannitol to the basic medium, (b) replacing 50 mM‐NaCl with 50 mM‐choline chloride, or (c) adding 5% human serum to the basic medium. 5. The addition of human serum to the perfusion medium depressed the fractional reabsorption of sodium and potassium; sodium from 0.94 +/‐ 0.01 (S.E. of mean) with the basic medium to 0.79 +/‐ 0.02 with basic medium +5% serum after 35 min perfusion; and potassium from 0.73 +/‐ 0.04 with the basic medium to 0.37 +/‐ 0.05 with the basic medium +5% serum after 35 min perfusion. 6. Two conclusions are drawn from the observations: first, that at the start of perfusion the effective internal osmolality of tubular cells of the outer medulla is greater than that of cortical cells and of the basic medium; and second, that the presence of small amounts of plasma proteins in the perfusion medium has a marked effect on the properties of plasma cell membranes.