bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermoregulatory responses to the injection of monoamines, acetylcholine and prostaglandins into a lateral cerebral ventricle of the echidna
Authors: Baird J. A. , Hales J. R. S. , Lang W. J.
Published: December 2014

1. The putative neurotransmitter substances 5‐hydroxytryptamine (5‐HT), noradrenaline (NA), acetylcholine (ACh) and prostaglandins E1 (PGE1) and E2 (PGE2) have been injected into a lateral cerebral ventricle of the conscious echidna (Tachyglossus aculeatus); thermoregulatory responses in thermoneutral (ambient dry bulb temperature, Tdb, of approximately 22° C), cool (Tdb of approximately 14° C) and warm (Tdb of approximately 26° C) environments were determined.

2. Under all conditions, all of the drugs tested either caused deep body temperature to fall or else had no effect; the fall was brought about by peripheral vasodilatation and/or reduced metabolic rate due to a decrease in shivering or to general relaxation.

3. Responses of the many placental mammals to 5‐HT, NA and ACh vary widely, and the echidna, a monotreme, appears to exhibit responses most like those of the rat.

4. Placental mammals tested to date invariably exhibit a hyperthermic response to prostaglandins, and the hypothermic responses of this monotreme is therefore unique. The present study included the confirmation of a hyperthermic response to PGE1 and PGE2 in cats and rats.

5. It is concluded that the concept of thermoregulation by amines and other substances in the hypothalamus of placental mammals may also be applicable to the monotremes which have evolved separately from the marsupials and placental mammals for about 180 million years.
Organization of corticofugal neurones in somatosensory area II of the cat
Authors: Atkinson D. H. , Seguin J. J. , Wiesendanger M.
Published: December 2014

1. This investigation had two main objectives: first to determine whether or not motor activity could be elicited by localized intracortical stimulation in somatosensory area II of the cat, and secondly to identify, by antidromic stimulation, neurones which projected to subcortical structures and to study their afferent input.

2. Although arm movements could be elicited in most cats by intracortical train stimulation with tungsten micro‐electrodes, the lowest motor thresholds were much higher than the lowest thresholds for the primary motor area under similar experimental conditions. Facial responses were evoked at lower stimulus thresholds, but the threshold decreased steadily as successive stimulation tracks approached the coronal face area. Previously observed responses to prolonged surface stimulation could have been caused by intracortical spread of excitation or by escape of stimulus to the primary area, especially the face area.

3. Neurones with corticofugal axons projecting to bulbar and spinal levels were first identified by their antidromic response to stimulation of the cerebral peduncle. Each was further tested by stimulation of the cervical corticospinal tract, and the dorsal column nuclei. Their receptive fields were then recorded.

4. It was possible to classify the neurones into four main categories: (i) non‐descending neurones: neurones not activated antidromically by any of the subcortical stimulating electrodes. The majority of these neurones had very small (lemniscal type) receptive fields, (ii) corticobulbar neurones: these were invaded antidromically by stimulation of the peduncle but not by spinal or dorsal column nuclei stimulation. They had ‘stocking‐like’ or larger receptive fields; (iii) cortico‐spinal neurones: neurones driven antidromically by stimulation of corticospinal fibres. Characteristically, these neurones had large confluent fields, often bilateral. Very few had receptive fields of the lemniscal type; (iv) neurones invaded by dorsal column nuclei stimulation: the number of such units was extremely low and their receptive fields were large or ‘stocking‐like’.

5. The results indicate that somatosensory area II in the cat does not exert an independent motor control of spinal neurones, and it is thought that corticofugal neurones of SII are involved in the control of somatosensory transmission rather than having a direct motor function.
The properties of motor units in a fast and a slow twitch muscle during post‐natal development in the kitten
Authors: Bagust J. , Lewis D. M. , Westerman R. A.
Published: December 2014

1. Motor units were functionally isolated from a fast and a slow twitch muscle of kittens: flexor digitorum longus (FDL) and soleus. Both muscles were examined in two groups: one aged about 2 weeks and the other 6 weeks.

2. A clear division into α and γ axons could be made. The mean conduction velocity of α axons from FDL was higher than that of soleus axons at both ages.

3. Tetanic tensions were expressed as a percentage of whole muscle tension. The distributions of motor unit tensions were symmetrical in soleus muscles but were skewed towards large values in FDL. In both types of muscle the scatter of motor unit tensions was greater at 2 weeks than at 6, the mean percentage tension also fell with age.

4. The motor unit twitch times to peak were symmetrically distributed in soleus but skewed towards large values in FDL. The variance was less than in adults.

5. Motor unit axonal conduction velocity was related to tetanic tension and twitch speed. The relationship between twitch time to peak and the ratio of twitch to tetanic tension varied with age but was not seen so clearly.
A study of the contractures induced in frog atrial trabeculae by a reduction of the bathing sodium concentration
Authors: Chapman R. A.
Published: December 2014

1. The relationship between the [Ca]o, the [Na]o and the strength of the contracture evoked when the [Na]o is reduced has been investigated in isolated frog atrial trabeculae.

2. The strength of the contracture varies by the [Ca]o2 and by 4√([Na]o) over the lower tension range.

3. The contracture induced by reduction of [Na]o is not sustained, but relaxes spontaneously. The rate of this relaxation is only dependent on the [Na]o is the presence of strophanthidin.

4. After the spontaneous relaxation of an Na‐free contracture, the ability of the trabecula to develop tension upon a second challenge with Na‐free solution returns in about 3 min if the muscle is perfused with Na‐containing fluid. This recovery process is slowed if the [Na]o is low during the recovery period, but the recovery is hastened by electrical stimulation of the preparation or by perfusion with K‐free or strophanthidin containing sodium‐Ringer.

5. It is suggested that the influx of Ca2+ which induces the Na‐free contracture depends on the presence of Na+ inside the cells. When the intracellular Na concentration falls, the Ca influx falls, and the muscle relaxes as a result of the activity of an intracellular relaxing structure.
An estimate of sodium/potassium pump activity and the number of pump sites in the smooth muscle of the guinea‐pig taenia coli, using 3[H]ouabain
Authors: Brading Alison F. , Widdicombe J. H.
Published: December 2014

1. Binding of tritiated ouabain to the smooth muscle of the guinea‐pig taenia coli showed two components, one saturable at lower glycoside concentrations and the other linear with increasing concentrations.

2. The saturable component alone was affected by extracellular potassium concentrations. This component seems to be bound to sodium pumping sites, and when completely saturated binds 1·1 × 1011 molecules per mg fresh wt. of tissue, or 250–300 molecules per square micron of membrane, assuming a volume:surface area ratio of 1·5 μm.

3. Only a fraction of 42K uptake by the cells can be blocked by ouabain at maximal concentrations. In normal Krebs solution two thirds can be blocked. The remaining one third is presumably passive uptake. The fraction blocked is reduced as the extracellular potassium concentration, and thus passive uptake, is increased.

4. The amount of potassium pumped into the cells at various concentrations of extracellular potassium has been calculated. In normal Krebs solution the amount pumped in 45 min was 20·0 m‐mole/kg fresh wt., and this was increased at higher potassium concentrations.

5. On the assumption of a stoichiometry of 3Na: 2K, the pump sites in normal Krebs solution have a turnover rate of 1320 min−1.

6. Indirect calculations of sodium movements suggest that the sodium permeability may be about 0·9 × 10−8 cm sec−1 and the pump may generate a current of 0·9 × 10−7 A cm−2. This crossing an Ohmic membrane resistance of 30–60 kΩ cm2 would be equivalent to a potential difference of 3–5 mV.
Responses in the rat thalamus to whisker movements produced by motor nerve stimulation
Authors: Brown A. W. S. , Waite Phil M. E.
Published: December 2014

1. The effect of electrical stimulation of the motor nerve supplying the whiskers on the activity of single cells in the vibrissal region of the ventrobasal complex of the thalamus has been studied in rats under urethane anaesthesia.

2. The stimulation caused protraction of the ipsilateral whiskers. 60% of the cells which fired to mechanical movements of the whiskers were found to respond to this electrical stimulus with 1–2 impulses at short latency (average 7·7 msec), provided the stimulus was sufficient to move the whiskers.

3. When the moving whiskers hit a barrier, 92% of the cells responded to the stimulus. The most effective position of the barrier was in front of the whiskers, although other positions often produced a response as well. Static displacement of the whiskers, particularly in the forward direction, could abolish the response or increase its latency.

4. The following‐frequencies for these cells were 5–10 stimuli/sec. Combinations of electrical stimuli with mechanical ramp movements of the whiskers showed that similar recovery times followed both types of stimuli.

5. These results are compared with those reported from studies in the afferent nerve fibres after electrical stimulation of the motor nerve and also with responses in the thalamus following mechanical movements of the whiskers. The possible importance of the latency of these sensory responses is considered.
The effect of the performance of work on total energy output and metabolism during muscular contraction
Authors: Curtin Nancy A. , Gilbert Claude , Kretzschmar K. M. , Wilkie D. R.
Published: December 2014

1. The production of heat (h) and work (w) and the changes in phosphocreatine (PCr) and ATP have been measured on tetanized isolated frog muscles (unpoisoned and in oxygen at 0° C) during shortening at constant velocity and during isometric contraction (both without relaxation). The former type of contraction was designed to maximize the fraction w/(h + w); the latter to minimize it.

2. The duration of the isometric contraction was made considerably longer than that of the isovelocity contraction so that the (h + w) productions during the two contractions were approximately equal.

3. The PCr break‐down during the working contraction was considerably greater than that during the isometric contraction.

4. No detectable ATP changes occurred.

5. The break‐down of PCr is sufficient to account for the work evolved: there is no reason to suppose that the work comes from an unidentified source.

6. In both types of contraction extra energy is evolved that cannot be accounted for by concurrent splitting of PCr. The time course of evolution of this extra energy is similar in all types of contraction, suggesting that it may arise from a process other than cross‐bridge interaction.

7. The results are discussed in terms of current cross‐bridge theory and muscle kinetics. The mean cycle times of a cross‐bridge during working and isometric contractions are 0·12 sec and 0·34 sec respectively. During the working contraction cross‐bridges spend about one quarter of the time attached to actin filaments.
Degeneration secretion of saliva in the rat following sympathectomy
Authors: Delfs Ursula , Emmelin N.
Published: December 2014

1. After previous extirpation of the superior cervical ganglion saliva was found to flow from the cannulated submaxillary duct of rats under chloralose anaesthesia. The secretion started 13–14·5 hr after sympathectomy, increased gradually in rate and then slowed down and ceased, lasting for about 12 hr.

2. Injection of α‐ or β‐adrenoreceptor blocking drugs reduced the flow and a combination of both types of drugs abolished it. It is concluded that the secretion was caused by noradrenaline released from the degenerating nerves, and that the phenomenon is an example of the degeneration activity described in other preparations as an effect of section of post‐ganglionic autonomic nerves.

3. A similar, but less pronounced, secretion was found in the parotid gland of the rat.
The effect of glucagon on the liver cell membrane potential
Authors: Petersen O. H.
Published: December 2014

1. Intracellular recordings of membrane potential were made from superficial cells of isolated mouse liver segments superfused with physiological salt solutions.

2. The mean resting cell membrane potential was −39·4 mV.

3. Glucagon caused a dose‐dependent membrane hyperpolarization which was detectable at 10−9
M and maximal (7 mV) at 10−7
M. The hyperpolarization started within half a minute after exposure to glucagon. Secretion (2 × 10−7
M) had no effect on the membrane potential.

4. Adrenaline (10−6
M) and isoprenaline (10−6
M) also caused membrane hyperpolarization (4–6 mV). The effect of isoprenaline, but not that of adrenaline, was blocked by propranolol (5 × 10−6
M).

5. Dibutyryl adenosine 3′,5′‐monophosphate (10−3
M) caused a membrane hyperpolarization of 4–8 mV.

6. In the absence of extracellular K or the presence of Strophanthin‐G (10−3
M) the resting potential was decreased and the response to glucagon reduced. During exposure to a solution containing 20 m
M‐K the resting potential was slightly enhanced and the amplitude of the glucagon‐induced hyperpolarization reduced compared with control conditions.

7. It is concluded that the effect of glucagon on the membrane potential is due to an interaction with specific membrane receptors probably leading to activation of the membrane‐bound adenyl cyclase. It is probable that the hyperpolarization is mediated by cyclic AMP. The hyperpolarization induced by glucagon is dependent on a normal function of the membrane Na—K pump.
The morphological types of ganglion cells of the domestic cat's retina
Authors: Boycott B. B. , Wässle H.
Published: December 2014

1. Three distinct morphological types of cat retinal ganglion cells have been identified and categorized as α, β and γ. Alpha ganglion cells have dendritic field diameters from 180 to 1000 μm; β, about 25 to 300 μm; γ, 180 to 800 μm, possibly more.

2. The dimensions of the α and β ganglion cell dendritic fields increase monotonically from the central area outwards to the periphery; those of the γ cells do not. Seemingly a spectrum of sizes of the γ cells is found at most locations in the retina.

3. All three morphological types of ganglion cells are found in the central area.

4. Possible further anatomical types of ganglion cells are discussed. Correlations are suggested between the morphological category α cells and the physiological class Y cells; between β cells and the X cells and between the γ cells and the W cells.
Chronic effects of botulinum toxin on neuromuscular transmission and sensitivity to acetylcholine in slow and fast skeletal muscle of the mouse
Authors: Tonge D. A.
Published: December 2014

1. A sublethal dose of botulinum toxin (type A) was injected into the muscles of one hind limb of the mouse causing local paralysis.

2. Neuromuscular transmission and muscle sensitivity to acetylcholine (ACh) were studied in vitro in soleus and extensor digitorium longus (EDL) from 6 hr to 4 months after the injection of toxin.

3. Both soleus and EDL failed to respond to nerve stimulation within 6 hr of the injection of toxin.

4. In muscle fibres in which neuromuscular transmission was blocked, subthreshold end‐plate potentials (e.p.p.s) were recorded. The amplitude of the e.p.p.s increased during recovery from the effects of the toxin and both muscles contracted in response to nerve stimulation after 2‐3 weeks.

5. For about 2 months muscles fatigued more rapidly than normal during repetitive nerve stimulation because of the low quantal content of e.p.p.s.

6. Supersensitivity to ACh developed in 3‐5 days and persisted after the return of neuromuscular transmission. Muscle sensitivity to ACh became normal when the rate of fatigue during nerve stimulation was normal.
Calcium release in relation to permeability changes in toad bladder epithelium following antidiuretic hormone
Authors: Cuthbert A. W. , Wong P. Y. D.
Published: December 2014

1. Methods for measuring the release of 45Ca from isolated urinary bladders of toads (Bufo marinus) pre‐loaded with this isotope have been devised. One method allowed separate collection from the mucosal and serosal surfaces of the bladders.

2. Reducing the ambient calcium concentration reduced the rate of 45Ca efflux suggesting that efflux of radiolabel represents calcium exchange.

3. Antidiuretic hormone, theophylline and prostaglandin E1 all increased calcium efflux, while lanthanum and amphotericin were without effect. Cyclic AMP caused only an inhibition of calcium release.

4. The increase in 45Ca efflux due to antidiuretic hormone came exclusively from the mucosal side. Experiments with EGTA suggest that the calcium entering the mucosal solution arises mainly from superficial sites in the mucosal membrane.

5. The release of 45Ca by hormone was not influenced by removal of sodium from the bathing solution. Low pH and amiloride reduced or abolished calcium release to hormone.

6. The time course of calcium release from the mucosal surface due to hormone was rapid (commencing between 0·5 and 1·5 min after hormone application). Thus calcium release precedes the increase in sodium transport and hydro‐osmotic flow following hormone, and appears to be at least as rapid as cyclic AMP generation in the tissue.

7. The relationship between calcium release or exchange and the permeability changes in the bladder to water and to sodium, following hormone, are discussed.
The sensitivity to glutamate of denervated muscles of the crayfish
Authors: Frank Eric
Published: December 2014

The effect of denervation on the sensitivity of muscle fibres to glutamate was studied in leg muscles of crayfish.

1. When the motor nerve was cut close to the proximal accessory flexor muscle the distal end of the nerve degenerated. Neuromuscular transmission failed and spontaneous miniature potentials disappeared after two months. Several stages of nerve terminal degeneration were seen in muscles denervated between 1 and 3 months, and after 4 months no remains of synapses could be found.

2. Following denervation for periods up to 8 months there was no significant change in sensitivity to glutamate, a substance that mimics the action of the neural transmitter. Depolarizations produced by various concentrations of glutamate in the bathing solution were the same in denervated and control muscle fibres. Moreover, the sensitivity to iontophoretically applied glutamate was localized to discrete patches as in innervated muscles.

3. Supersensitivity of muscles apparently does not occur after denervation in the crayfish.
Localization of beta adrenergic receptors, and effects of noradrenaline and cyclic nucleotides on action potentials, ionic currents and tension in mammalian cardiac muscle
Authors: Reuter H.
Published: December 2014

1. Isoprenaline and noradrenaline were applied iontophoretically to cardiac Purkinje fibres. Intracellular application of the drugs had no effect, while extracellular application of the same amounts of charge caused acceleration of pace‐maker activity and a shift of the plateau level of the action potential. These results indicate that β‐adrenergic receptors are located at the outside of the cardiac cell membrane.

2. A systematic comparison of the effects of cyclic AMP derivatives and noradrenaline on action potentials and isometric tension of ventricular myocardial preparations showed that the nucleotides and the catecholamine increase the plateau height and the duration of the action potential and also increase tension. However, there are quantitative differences in the action of these drugs.

3. Cyclic AMP derivatives and noradrenaline increase the slow inward current, ICa, in ventricular myocardial preparations. Voltage clamp analysis of ICa showed that the kinetic parameters of this membrane current are not affected by these drugs. However, the membrane conductance to Ca ions is greatly increased by noradrenaline and to a smaller extent by dibutyryl cyclic AMP.

4. Concentration—response relations of the membrane effects of noradrenaline on plateau height of the action potential and on ICa could be fitted by the same theoretical log concentration—response curve. The Hill plot of this concentration—response curve had a slope of 2. The half maximal response occurred at 5 × 10−7
M.

5. The results are compared with other membrane effects of catecholamines and cyclic nucleotides in cardiac muscle. The effects on ICa are related to the positive inotropic effect of the drugs.
Transport of rubidium and sodium in pancreatic islets
Authors: Sehlin J. , Täljedal I.‐B.
Published: December 2014

1. Fluxes of 86Rb+ and 22Na+ were measured in pancreatic islets of ob/ob‐mice. The islets, which contain more than 90% β‐cells, were incubated at 37° C in Krebs—Ringer bicarbonate buffer with modifications known to influence insulin release.

2. In the presence of Na+, the islets vigorously accumulated Rb+. The Rb+ uptake was inhibited by depletion of islet Na+ or by 1 m
m ouabain or 0·1 m
m chloromercuribenzene‐p‐sulphonic acid. Rb+ uptake was stimulated by 1 m
m‐5,5′‐dithiobis (2‐nitrobenzoic acid) or by depletion of islet Ca2+, while 20 m
m glucose, 5 m
m theophylline, 0·1 m
m iodoacetamide, or 1 m
m‐6,6′‐dithionicotinic acid had no significant effects.

3. The efflux of Rb+ from preloaded islets followed exponential kinetics with a half‐life of about 16 min. The rate of efflux was enhanced by 0·1 m
m chloromercuribenzene‐p‐sulphonic acid and inhibited by 20 m
m glucose. Omission of Na+, K+ or Ca2+ from the incubation medium had no significant effects.

4. The efflux of 22Na+ from islets preloaded with this isotope was enhanced by 0·1 m
m chloromercuribenzene‐p‐sulphonic acid or by Ca2+ deficiency. It was inhibited by 1 m
m ouabain, 0·1 m
m‐2,4‐dinitrophenol, or by omission of Na+ from the incubation medium. Omission of K+ or the addition of 20 m
m glucose had no significant effects.

5. It is concluded that the β‐cells are permeable to Na+ and Rb+ and expel Na+ by an active mechanism similar to, or identical with, the Na+/K+‐pump in other cells. The mechanisms of active and passive cation movements are discussed in relation to current hypotheses of stimulus‐secretion coupling in the β‐cells depending on interactions between Na+ and Ca2+. In particular, the results support the hypotheses of insulin release being stimulated by ouabain through inhibition of the Na+/K+‐pump and by organic mercurials through enhancement of membrane permeability to cations.
Electrical responses of double cones in the turtle retina
Authors: Richter Amrei , Simon E. J.
Published: December 2014

1. Responses to monochromatic flashes were recorded intracellularly from double cones in the retina of the turtle, Pseudemys scripta elegans. Double cones have been identified by intracellular marking with Procion Yellow dye.

2. The direct light response of a double cone is a hyperpolarization graded with the intensity of a flash and similar to the response of single cones.

3. When flashes were dim, responses were proportional to light intensity but varied in time course as a function of wave‐length. They reached peak in about 120 msec for deep red stimuli and about 143 msec for green stimuli.

4. When applied over red backgrounds, responses to red flashes became smaller, faster and frequently diphasic, but responses to green remained similar to those recorded from darkness. Green backgrounds made responses to all colours small and fast.

5. Linear spectral sensitivity curves have peaks corresponding to the peak sensitivities of single red‐sensitive and green‐sensitive cones. Red and green backgrounds suppressed red and green sensitivity respectively.

6. Large fields of illumination evoked composite responses which included the direct light response, its enhancement from illumination of nearby receptors and the depolarizing effect of luminosity horizontal cell impingement. In the green‐sensitive element the depolarizing effect was larger for red than for green flashes, and stimulation with red annuli evoked net depolarizing responses.

7. It is concluded that the responses of double cones may be explained by coupling of the responses from red‐sensitive and green‐sensitive elements each of which has properties otherwise similar to single red‐sensitive and green‐sensitive cones.
The electrical response of turtle cones to flashes and steps of light
Authors: Baylor D. A. , Hodgkin A. L. , Lamb T. D.
Published: December 2014

1. The linear response of turtle cones to weak flashes or steps of light was usually well fitted by equations based on a chain of six or seven reactions with time constants varying over about a 6‐fold range.

2. The temperature coefficient (Q10) of the reciprocal of the time to peak of the response to a flash was 1·8 (15‐25° C), corresponding to an activation energy of 10 kcal/mole.

3. Electrical measurements with one internal electrode and a balancing circuit gave the following results on red‐sensitive cones of high resistance: resistance across cell surface in dark 50–170 MΩ; time constant in dark 4‐6·5 msec. The effect of a bright light was to increase the resistance and time constant by 10–30%.

4. If the cell time constant, resting potential and maximum hyperpolarization are known, the fraction of ionic channels blocked by light at any instant can be calculated from the hyperpolarization and its rate of change. At times less than 50 msec the shape of this relation is consistent with the idea that the concentration of a blocking molecule which varies linearly with light intensity is in equilibrium with the fraction of ionic channels blocked.

5. The rising phase of the response to flashes and steps of light covering a 105‐fold range of intensities is well fitted by a theory in which the essential assumptions are that (i) light starts a linear chain of reactions leading to the production of a substance which blocks ionic channels in the outer segment, (ii) an equilibrium between the blocking molecules and unblocked channels is established rapidly, and (iii) the electrical properties of the cell can be represented by a simple circuit with a time constant in the dark of about 6 msec.

6. Deviations from the simple theory which occur after 50 msec are attributed partly to a time‐dependent desensitization mechanism and partly to a change in saturation potential resulting from a voltage‐dependent change in conductance.

7. The existence of several components in the relaxation of the potential to its resting level can be explained by supposing that the ‘substance’ which blocks light sensitive ionic channels is inactivated in a series of steps.
The inhibitory effect of the cerebellar fastigial stimulation on ADH secretion
Authors: Hata Namiyo , Miura Mitsuhiko
Published: December 2014

1. Both cardiovascular and antidiuretic hormone (ADH) responses to some neural inputs were examined in paralysed anaesthetized cats.

2. Carotid occlusion elicited cardiovascular responses and increased ADH secretion. When the electrical stimulation of discrete loci of the cerebellar fastigial nucleus (fastigial pressor area) was superimposed on carotid occlusion, cardiovascular responses were further facilitated, while ADH secretion was inhibited.

3. The fastigial stimulation alone elicited facilitory cardiovascular responses composed of hypertension and tachycardia, and the fastigial pressor response (FPR), but did not evoke any consistent ADH response.

4. These facts indicate that cerebellar modulation of ADH secretion occurs not directly via the hypothalamo‐hypophysial system but through the lower brain stem to which both carotid sinus nerves and outflows from the fastigial pressor area project.

5. We conclude that the fastigial pressor area is specific for not only cardiovascular and other autonomic responses but pituitary hormonal response.
Responses of olfactory bulb neurones to odour stimulation of small nasal areas in the salamander
Authors: Kauer John S. , Moulton David G.
Published: December 2014

1. Previous experiments have suggested that one way odours may be discriminated is by different spatial patterns of response at both the olfactory bulb and receptor level. The present experiments were designed to test to what extent the position of an odour on the receptor mucosa can influence the activity of olfactory bulb neurones.

2. To deliver odours to small areas on the nasal receptor sheet a new method for local application of odour was developed. The flow rate, concentration, and time course of the odour were controlled using the olfactometer described in the preceding paper.

3. In thirty olfactory bulb units in the salamander it was found that if the response of a unit to odour delivered to the entire exposed receptor epithelium were suppression (type S), then the unit tended to be suppressed when odour was delivered to a number of localized epithelial regions. If the response were excitation (type E) to stimulation of the entire epithelium, then stimulation to only one or two localized regions would elicit the maximum response.

4. Different epithelial regions had the ability to cause excitation in the same bulbar unit depending on the odour being used. Two odours, camphor and amyl acetate, elicited maximum excitation when they were presented to different mucosal areas. The areas at which presentation of these odours gave excitation were surprisingly consistent from unit to unit and animal to animal.

5. The data presented here suggest the presence of restricted excitatory receptive fields for some olfactory bulb neurones for a particular odour.

6. The presence of spatial response patterns using odour delivery to small nasal receptor regions and thus the presence of receptive fields is discussed with reference to bulbar neuronal circuitry.
Axonal surface charges: binding or screening by divalent cations governed by external pH
Authors: D'arrigo J. S.
Published: December 2014

1. The effect of different extracellular alkaline‐earth cations (Ca2+, Mg2+, Sr2+, Ba2+) upon the threshold membrane potential for spike initiation in crayfish axon has been studied by means of intracellular micro‐electrodes. This was done at the following pHs of the bathing saline: 6·00, 5·35, 5·00, and 4·65 ± 0·05.

2. At pH 6·00, the four alkaline earths had essentially the same effect upon the threshold membrane potential.

3. At pH 5·35 or lower, it was found that equal concentrations of the alkaline‐earth cations did not have the same effect on the threshold potential. The selectivity sequences observed at the different pHs were: pH 5·35, Ca2+ > Mg2+ > Sr2+ ≥ Ba2+; pH 5·00, Ca2+ ≃ Ba2+ > Sr2+ ≥ Mg2+; pH 4·65, Ba2+, Sr2+ > Ca2+ > Mg2+.

4. It is shown that the individual selectivity sequences are predicted rather closely by the equilibrium selectivity theory for alkaline‐earth cations.

5. It is concluded that the only difference between excitable cells which show screening and those which bind divalent cations is the net density of ionized, surface acidic groups in the region of the sodium gates.
Histamine‐stimulated hydrogen ion secretion by in vitro piglet gastric mucosa.
Authors: Forte J G , Forte T M , Machen T E
Published: December 2014

1. A new preparation of gastric mucosa isolated from new‐born piglets is described. The piglet gastric mucosa was easily separated from the serosal muscle layers by a "blistering" technique which appeared to cause minimal trauma to the tissue and which allowed extended study in vitro in a suitable chamber. Normal resting p.d. was approximately minus 30 mV (mucosal side negative with respect to serosal side), resistance about 100 omega. cm‐2 and H+ secretion was absent or occurred at very low rates (0–1mu‐equiv/cm‐2. hr). 2. Maximally stimulating doses of histamine (1–6 times 10–5 M) caused H+ secretion to increase (up to 15 muequiv/cm‐2. hr), p.d. to increase and resistance to decrease. A close correlation was observed between the increase in H+ secretion and decrease in transmucosal resistance. The threshold dose of histamine appeared to be 10–8 M; concentrations 10–4 M and higher reduced H+ secretion somewhat. 3. Pentagastrin (10‐9‐10‐7 M) and acetylcholine (10‐7‐10‐5 M) did not significantly stimulate the piglet gastric mucosa. Pentagastrin concentrations above 4 times 10‐6 M reversibly inhibited H+ secretion of histamine‐stimulated mucosa. High concentrations of acetylcholine (above 4 times 10‐4 M) did not affect histamine‐stimulated H+ secretion, but a significant reduction in p.d. was observed. 4. This investigation demonstrates the utility of the piglet gastric mucosa for in vitro studies of the mechanism H+ secretion and the action of secretagogues. From a consideration of such factors as the thinness of tissue and ease of preparation it is suggested that neonatal animals may represent a good source of in vitro mammalian gastric tissue.
Transport and electrical phenomena in resting and secreting piglet gastric mucosa.
Authors: Forte J G , Machen T E
Published: December 2014

1. Gastric mucosae were isolated from piglets (0–5 days old) and mounted in a chamber where electrical properties and secretory function could be measured. Unlike many previously reported mammalian in vitro preparations, pig gastric mucosae were stable and physiologically responsive for many hours after isolation. 2. With similar Ringer solutions bathing both surfaces, the isolated piglet gastric mucosa maintained a p.d. with the mucosal surface 30–35 mV negative with respect to the serosal surface. Limitation of access of Na+ from the mucosal bathing solution to the tissue (e.g. replacement of Na+ on mucosal side with choline or treatment with 10‐ minus 5 M amiloride) produced a decrease in p.d. and increase in mucosal resistance consistent with an hypothesis of Na+ transport from mucosa to serosa. 3. Isotopic flux measurements (36Cl and 24Na) and net H+ secretory rate were performed during open and short‐circuit conditions, while the tissue was at rest and after stimulation of HCl secretion by 6 times 10‐ minus 5 M histamine. Up to 90% of the respective short‐circuit current for resting or secreting mucosae was accounted for as the algebraic sum of Cl minus, H+ or Na+ fluxes. 4. The net transport of Na+ which occurred from mucosa to serosa during rest (ca. 4‐7 muequiv/cm2.hr) was somewhat reduced during HCl secretion (ca. 2‐7 muequiv/cm2.hr). This active transport of Na+ was more resistant to anaerobiosis than was H+ or Cl minus transport. 5. An active transport component of Cl minus from serosa to mucosa was clearly demonstrable in the non‐secreting preparations (ca. 3‐9 muequiv/cm2.hr). Active Cl minus transport was stimulated three‐ to fourfold after H+ secretion was stimulated by histamine. Anaerobiosis promptly reduced Cl minus and H+ transport. An exchange diffusion component was demonstrated for Cl minus which appeared to be prominent during H+ secretory activity and was considerably diminished in resting mucosae. 6. Large changes in mucosal resistance were associated with conditions of rest, histamine stimulation and anaerobic conditions; mean values were 113, 74 and 197 omega.cm2, respectively. Electrical conductance of the isolated gastric mucosa was due primarily to partial ionic conductance of Cl minus (60–65%) and Na+ (10–15%). The partial conductance of H+ was extremely low. The observed increase in tissue conductance associated with H+ secretory activity and the changes in the long‐time constant p.d. transient to a current pulse are discussed in terms of the relative contribution of the serosal and mucosal plasma membrane surfaces.
Monosynaptic connexions among Aplysia neurones examined by the intracellular application of tea.
Authors: Bryant H L , Weinreich D
Published: December 2014

1. Several assumptions underlying the use of intracellularly applied tetraethylammonium (TEA) for assessing monosynaptic connexions were evaluated in identified neurones of Aplysia. 2. In the R2 neurons, intrasomatic TEA application prolongs the duration of the intrasomatically recorded action potential. Subsequently, the action potential in the axon of R2, recorded extracellularly 4‐7 mm from the soma, was also prolonged. 3. Intracellular application of TEA into the somata of the multi‐action interneurone L10 enhances the duration of the L10 AP and results in larger and more prolonged post‐synaptic potentials (p.s.p.s) recorded from neurones believed to be connected monosynaptically with L10. The action potential duration and wave form of p.s.p.s elicited by nerve stimulation in these same post‐synaptic neurones were unaffected during the time L10‐mediated p.s.p.s were potentiated. 4. Following TEA injection into L10 the p.s.p. recorded in neurone L7 changes wave form in a manner similar to that observed when L10 is tetanized. 5. It is concluded that TEA migrates from its intracellular site of application, does not leave the injected neurone in significant quantities, and alters the wave form of the p.s.p in only those neurones connected monosynaptically to the injected neurone.
Effects of dopamine on carotid chemo‐ and baroreceptors in vitro.
Authors: Zapata P
Published: December 2014

1. The effects of dopamine on the sensory discharges originating from arterial chemo‐ and baroreceptors were studied in vitro using carotid bodies or sinuses excised from anaesthetized cats and superfused with Locke's solution. 2. Intrastream injections of dopamine 10–200 mug produced a transient depression of the frequency of chemoreceptor discharges. This effect was observed in response to the first injection in eighteen out of twenty preparations. 3. The inhibitory effect of dopamine can counteract partially or totally the excitation of chemoreceptors evoked by simultaneous application of acetylcholine or cyanide. 4. This inhibitory effect of dopamine is reduced or abolished by pretreatment with dopaminergic (Spiroperidol) or alpha‐adrenergic (Dibenamine) blockers. 5. In response to repeated injections of dopamine applied at short intervals, the inhibitory effect is replaced by a biphasic effect (early inhibition followed by late excitation), a late and long‐lasting excitation or no changes in chemoreceptor activity. The late excitatory effects of dopamine are not blocked by dopaminergic or alpha‐adrenergic blockers. 6. Noradrenaline does not affect the chemoreceptor activity of the superfused carotid body. DL‐DOPA induces only a late and long‐lasting excitatory effect. 7. In carotid sinus preparations, dopamine induces a weak but long‐lasting increase in the frequency of baroreceptor discharges. 8. It is concluded that dopamine may play a modulatory role in the generation of chemoreceptor activity through local regulatory processes.
Elicidation by a H‐2‐receptor antagonist of the significance of mucosal histamine mobilization in exciting acid secretion.
Authors: Lundell L
Published: December 2014

1. The consequence of H‐2‐receptor blockade for the secretory responses of the gastric mucosa to hormonal or cholinergic stimulation was studied in conscious rats with Heindenhain pouches or Pavlov pouches with the antrum retained or resected. 2. Metiamide almost completely abolished acid secretion induced by pentagastrin without altering significantly the amount of histamine excreted in the urine. Histamine mobilization on pentagastrin infusion determined in vitro, seemed to be larger during H‐2‐receptor blockade than with pentagastrin alone. 3. CCK‐PZ mobilized mucosal histamine to a considerable extent; the secretory response to this hormone was completely abolished by H‐2‐receptor blockade. 4. Acid secretion in response to 2‐deoxy‐D‐glucose was inhibited by H‐2‐receptor blockade in the presence or absence of the antrum; however the inhibition was less complete than with hormone‐induced secretion. 5. The acid secretory response to 100 mg/kg of 2‐deoxy‐D‐glucose appeared to be less susceptible to H‐2‐receptor blockade than that of 50‐mg/kg of 2‐deoxy‐D‐glucose. 6. Feeding induced a secretory response in the Pavlov pouch which initially was more effectively inhibited by H‐2‐receptor blockade than the response to 2‐deoxy‐D‐glucose. In the absence of antral gastrin secretion by either stimulus was equally inhibited. 7. Methacholine‐induced acid secretion was inhibited by infusion of the H‐2‐receptor antagonist, an inhibition that was absent when pentagastrin was concomitantly infused. 8. Although acid secretion induced by cholinergic stimuli was readily inhibited by the H‐2‐receptor antagonist, slight or nor inhibition was noted on pepsin secretion. 9. The role of histamine as a physiological stimulus for the parietal cell is discussed in view of the fact that the secretory effect of natural stimuli, known or demonstrated to mobilize mucosal histamine, is restrained by H‐2‐receptor blockade.
Effects of some aliphatic alcohols on the conductance change caused by a quantum of acetylcholine at the toad end‐plate.
Authors: Gage P W , McBurney R N , Schneider G T
Published: December 2014

1. The post‐synaptic effects of the aliphatic alcohols, ethanol to hexanol, were investigated at the neuromuscular junctions of toads, with particular emphasis on the effects of ethanol. 2. The alcohols increased the amplitude and duration of miniature end‐plate potentials. It is shown that this effect was due to the prolongation of the decay phase of miniature end‐plate currents (m.e.p.c.s). There was no effect of alcohols on the growth phase of m.e.p.c.s. 3. The prolonged decay of m.e.p.c.s in ethanol remained exponential and was normally sensitive to membrane potential. Prolonged m.e.p.c.s were associated with an equivalent prolongation of the mean duration of elementary events, as determined from power spectra of acetylcholine noise in 0–5 M ethanol. 4. The relationship betweeen the time constant of decay of m.e.p.c.s (tau) and the concentration of an alcohol of carbon chain length N (C‐N) was exponential, conforming to the equation tau equals tau‐s exp (B‐N‐C‐N), in which tau‐s is the decay time constant in standard solution and B‐N is a constant, different for each alcohol. 5. There was also an exponential relationship between B‐N and N, which closely followed the relationship between membrane‐buffer partition coefficient and carbon chain length for the different alcohols, indicating that the alcohols are active in the lipid phase of the post‐synaptic membrane. 6. It is suggested that the alcohols act by causing a change in the dielectric constant of the post‐synaptic membrane which forms the environment of the rate‐limiting reaction responsible for the decay of the end‐plate conductance. On the assumption that this reaction involves dipoles, it is shown that the small changes in dielectric constant, calculated from the partition coefficients of the alcohols and by assuming an initial lipid dielectric constant of 3, would give an exponential relationship between the time constant of decay of m.e.p.c.s and alcohol concentration. 7. The results support the hypothesis that the decay (but not the onset) of acetylcholine‐induced conductance changes is rate‐limited by a first‐order reaction which involves dipoles and occurs in the lipid environment of the post‐synaptic membrane.
Physiological properties of junctions between nerve and muscle developing during salamander limb regeneration.
Authors: Dennis M J
Published: December 2014

1. Physiological properties of developing nerve‐muscle junctions were studied in regenerating limbs of adult salamanders. 2. During the period of synapse formation the muscle fibres had diameters of 4‐10 mum, resting potentials of minus 90 to minus 100 mV and input resistances of 10–50 Momega. Some, but not all, pairs of adjacent muscle fibres were electrically coupled. 3. At the stage when muscle fibres could first be identified, some of them were not innervated, at least as determined by electrophysiological criteria. 4. During muscle innervation the neuromuscular synapses were encountered in several intermediate phases of maturity. (i) At the least mature junctions small spontaneous synaptic potentials occurred, but stimulation of the motor nerve trunk did not evoke synchronous transmitter release. (ii) At other junctions maximal nerve stimulation evoked only a single end‐plate potential of low quantum content. (iii) More mature fibres received synaptic input from as many as four motor neurons, which could be distinguished by their discrete stimulus thresholds. 5. During this period of synapse development the fibres lacked an action potential but often showed a prolonged response to depolarization. 6. Fibres in normal adult muscles had from one to three synaptic inputs, were not electrically coupled, and responded to depolarization with an action potential.
The effect of a chronic lesion in cortical area 17 on the visual responses of units in area 18 of the cat.
Authors: Donaldson I M , Nash J R
Published: December 2014

1. Lesions were made in cortical Area 17 (Visual I) of eight cats which were then allowed to recover. 2. During acute experiments between 1 and 11 weeks after the lesion the activity of Area 18 (Visual II) units was recorded and the results were compared with those obtained in normal cats. 3. The receptive fields were similar in size and distribution in the two groups but the lesioned animals had a much higher proportion of units unaffected by a visual stimulus and a higher proportion of the visually responsive units lacked specific direction or orientation preference. 4. Of six units which were tested in Area 18 of cats with lesions five showed variability of their direction or orientation preference with time. 5. The effects described above are most probably due to destruction of the corticocortical pathway which connects Areas 17 and 18. Some units in Area 18 appear to be driven by visual stimuli via their geniculate input alone. The corticocortical (Area 17 to 18) pathway may normally confer additional specificity on some of these units.