bluuebunny/crossref_metadata_2025 huggingface dataset:
Adrenal and pancreatic endocrine responses to hypoxia and hypercapnia in the calf.
Authors: Bloom S R , Edwards A V , Hardy R N
Published: December 2014

1. Adrenal and pancreatic endocrine responses to hypoxia and hypercapnia, of differing degrees of intensity, have been examined in conscious, unrestrained calves 3‐5 weeks after birth. 2. The outputs of cortisol and corticosterone from the right adrenal gland were found to vary inversely with arterial Po2 between 17 and 55 mmHg. Significant increase in mean adrenal blood flow was not observed at arterial oxygen tensions above about 30 mmHg. 3. Release of physiologically effective amounts of catecholamines from the adrenal medulla occurred only in response to intense hypoxia (arterial Po2 17‐1 +/‐ 2‐8 mmHg) and was effectively abolished by section of both splanchnic nerves. Release of pancreatic glucagon in response to such intense hypoxia was unaffected by section of both splanchnic nerves and administration of atropine. In contrast, the rise in plasma pancreatic glucagon concentration during less intense hypoxia was abolished by autonomic blockade. 4. Hypercapnia produced by inhalation of either 5% or 10% CO2 for 30 min stimulated maximal release of adrenal glucocorticoids and caused a substantial rise in plasma glucagon concentration. In contrast, the adrenal medulla was found to be extremely resistant to hypercapnia. Significant release of catecholamines was only observed during intense hypercapnia (inhalation of 10% CO2) and noradrenaline was invariably found to be the predominant amine. 5. The results of these experiments show how endocrine responses to hypoxia and hypercapnia are graded in the conscious calf. Of the mechanisms we have examined the pituitary‐adrenal cortical axis is the most sensitive and the adrenal medulla the most resistant, while the pancreatic alpha cell occupies an intermediate position.
The control of shivering and non‐shivering thermogenesis in the rat.
Authors: Banet M , Hensel H
Published: December 2014

1. The effect of intraperitoneal administration of propranolol (4, 8 and 12 mg/kg) on colonic temperature was studied in twelve rats during exposure to ambient temperatures of 30, 15 and 5 degrees C. 2. At 30 degrees C, propranolol had no effect on colonic temperature; at 15 and 5 degrees C, however, 4 mg propanolol/kg induced a fall in colonic temperature of about 0‐8 degrees C, whereas 8 and 12 mg propanolol/kg induced a fall of about 1‐5‐2‐0 degrees C. 3. Assuming that the temperature regulations system of the rat has a proportional controller and that the effect of propranolol was due to the blockade of non‐shivering thermogenesis, the results are interpreted as showing that shivering is activated only when heat loss exceeds the capacity for non‐shivering thermogenesis.
Pancreatic acinar cells: localization of acetylcholine receptors and the importance of chloride and calcium for acetylcholine‐evoked depolarization
Authors: Iwatsuki N. , Petersen O. H.
Published: December 2014

1. Intracellular micro‐electrode recordings of acinar cell membrane potential and resistance were made from the mouse pancreas superfused in vitro. The acinar cells under investigation were stimulated by micro‐iontophoretic ACh application from an extracellular AChCl‐filled micro‐electrode.

2. Passing short‐lasting ejecting current pulses through the AChCl‐electrode caused acinar cell depolarization when the electrode was in an extracellular position not far (< 50 μm) from an acinus impaled by a KCl micro‐electrode. After insertion of the AChCl electrode into a neighbouring acinar cell, electrically coupled to the acinar cell already impaled by the KCl‐electrode, ejecting ACh current pulses only affected the membrane potential in a direct electrical manner whereas there was no sign of an effect of ACh on the membrane potential.

3. Replacing extracellular chloride by sulphate caused a marked increase in the amplitude of the ACh‐evoked depolarization. If the membrane potential was recorded with a KCl electrode ACh continued to evoke very large depolarizations even after more than 1 hr exposure to Cl‐free solution. If the membrane potential was recorded with a K‐citrate electrode the effect of Cl‐removal was only transient. Removal of Na+ during exposure to Cl‐free solution reduced the amplitude of the ACh‐evoked depolarization somewhat. Readmission of Cl after more than 1 hr of Cl deprivation caused an immediate reversal of the ACh effect into a hyperpolarization.

4. Removal of extracellular Ca2+ caused a marked reduction in the amplitude of small depolarizations evoked by just suprathreshold doses of ACh, whereas there was very little effect on larger depolarizations evoked by maximal or supramaximal ACh ejections. The effect of Ca removal was fully reversible. Addition of Mn after Ca‐deprivation was as efficient as Ca in restoring normal electrophysiological responses to small doses of ACh.

5. The acinar cell membrane seems only to be responsive to ACh added to the extracellular side and ACh probably causes an increase in membrane Cl permeability in addition to the previously described effects on Na and K permeability. Ca may be important in determining ACh receptor sensitivity.
The dependence of the electrical potentials across the membranes of the frog skin upon the concentration of sodium in the mucosal solution.
Authors: Nagel W
Published: December 2014

1. The dependency of the transmembranal potential differences upon the [Na] of the mucosal bathing solution was investigated in frog skin. Semilogarithmic linear correlations were obtained between [na]0 and the transepithelial potential difference (slope: 28‐4 +/‐ 1‐8 mV/dec [Na]0), the potential differences across the outer and the inner membrane under open circuit conditions (slope: 33‐4 +/‐ 1‐8 and 4‐8 +/‐ 1‐5 mV/dec [Na]0, respectively) and the intracellular potential under short circuit conditions (slope: 33‐3 +/‐ 3‐4 mV/dec [Na]0). 2. No difference could be observed between skins incubated in Cl‐ or SO4‐Ringer. 3. The results are not in accordance with the Koefoed‐Johnsen & Ussing hypothesis. Neither the polarity of the postulated Na electrode at the outer border could be obtained nor the expected slope of the dependency between potential gradient and [Na] of the mucosal bathing solution. 4. Current recirculation through paracellular shunt pathways is suggested to explain the deviation, at least in part. In addition, the I‐R‐drop resulting from Na entry across the outer border might account for part of the changes of potential gradients. 5. Under all conditions, Na uptake occurs energetically downhill, but permeability changes of the outer border must be postulated to explain the observed dependency of net Na transport upon [Na]0.
Active Na—K transport and the rate of ouabain binding. The effect of insulin and other stimuli on skeletal muscle and adipocytes
Authors: Clausen Torben , Hansen Otto
Published: December 2014

1. The effect of stimulation or inhibition of active Na—K transport on [3H]ouabain binding has been investigated in isolated soleus muscles and adipocytes.

2. In rat soleus muscle, the ouabain‐sensitive component of 42K influx was stimulated by insulin (100 m‐u/ml.), adrenaline (6 × 10−6
M), and by pre‐incubation with veratrine (10−5
M) or in a K‐free buffer. In all of these instances, the rate of ouabain binding was increased by 41‐113%. Conversely, pre‐treatment with tetracaine (0·2 m
M) decreased the 42K‐influx and diminished the rate of [3H]ouabain binding by 36%.

3. Neither insulin, adrenaline or tetracaine produced any detectable change in the total number of ouabain‐binding sites (as measured under equilibrium conditions) in rat soleus muscle.

4. In mouse and guinea‐pig soleus muscle and in fat cells isolated from rats, insulin also increased the rate of [3H]ouabain binding without producing any significant change in the total number of ouabain‐binding sites.

5. Both in soleus muscle and the epididymal fat pad of the rat, there was a linear correlation between 42K influx and the initial rate of [3H]ouabain binding.

6. It is concluded that the rate of ouabain binding is determined significantly by the rate of active Na—K transport, but within the time intervals studied (4‐6 hr) stimulation or inhibition of the Na pump does not lead to any appreciable change in the total number of Na pumps. It seems unlikely that the stimulation of active Na—K transport by insulin or adrenaline is due to unmasking or de novo synthesis of Na pumps.
Action potentials in slow muscle fibres of the frog during regeneration of motor nerves.
Authors: Schmidt H , Stefani E
Published: December 2014

1. Pyriformis muscles of Rana temporaria were denervated by crushing the sciatic nerve inside the pelvis. At different times during regeneration of the nerve, slow muscle fibres were examined for the presence of all‐or‐none responses. 2. During the early period of re‐innervation (35‐60 days), slow muscle fibres were found to be non‐selectively re‐innervated by (foreign) fast‐conducting motor axons. All slow fibres during this period were able to produce full sized action potentials, with overshoot. 3. Action potentials markedly decreased in amplitude and eventually disappeared completely between day 61‐110 following denervation; during this period, slow muscle fibres were re‐innervated by slowly‐conducting motor axons. 4. Functional re‐innervation by slowly‐conducting motor axons, in the late stages of re‐innervation, was not a necessary condition for the suppression of the action potential. Slow fibres innervated by fast motor axons, as well as denervated slow fibres, lost the action potential simultaneously with slow fibres which were re‐innervated by slowly‐conducting motor axons. 5. It is suggested that (small) slowly‐conducting motor axons can exert a 'trophic' influence on the slow fibre membrane, independent of their synaptic function.
Developmental changes in the inward current of the action potential of Rohon‐Beard neurones
Authors: Baccaglini Paola I. , Spitzer Nicholas C.
Published: December 2014

1. Rohon‐Beard cells in the spinal cord of Xenopus tadpoles have been studied in animals from early neural tube to free‐swimming larval stages. The onset and further development of electrical excitability of these neurones has been investigated in different ionic environments, to determine the ionic species carrying the inward current of the action potential.

2. The cells appear inexcitable at early stages (Nieuwkoop & Faber stages 18‐20) and do not give action potentials to depolarizing current pulses.

3. The action potential is first recorded at stage 20. (A) The inward current is carried by Ca2+ at stages 20‐25, since it is blocked by m
m quantitites of La3+, Co2+ or Mn2+ and is unaffected by removal of Na+ or the addition of tetrodotoxin (TTX). (B) The action potential is an elevated plateau of long duration (mean 190 msec at stages 20‐22). The duration decreases exponentially with repetitive stimulation. (C) The specific Ca2+ conductance (gCa) at the onset of the plateau of the action potential is 2·6 × 10−4 mho/cm2. Calculations show that a single action potential raises [Ca2+]1 by more than 100‐fold.

4. At later times (stages 25‐40), the inward current of the action potential is carried by both Na+ and Ca2+: the action potential has two components, an initial spike which is blocked by removal of Na+ or addition of TTX, followed by a plateau which is blocked by La3+, Co2+ or Mn2+.

5. Finally (stages 40‐51), the inward current is primarily carried by Na+, since the action potential is blocked only by removal of Na+ or addition of TTX, and the overshoot agrees with the prediction of the Nernst equation for a Na‐selective membrane. When the outward current channel is blocked and cells exposed to Na‐free solutions, 67% of cells at the latest stages studied were incapable of producing action potentials in which the inward current is carried by divalent cations.

6. The duration of the action potential decreases from a maximum of about 1000 msec to about 1 msec during development. The maximum input resistance (Rin) decreases from ca. 1000 to 100 MΩ.

7. The calcium action potential may play a role in the development of excitability and the growth of the neurones.
Brain stem stimulation and the acetylcholine‐evoked inhibition of neurones in the feline nucleus reticularis thalami
Authors: Dingledine Raymond , Kelly J. S.
Published: December 2014

1. In cats anaesthetized with halothane and nitrous oxide, the responses to iontophoretically applied acetylcholine (ACh) and to high‐frequency stimulation of the mid‐brain reticular formation (MRF) were tested on spontaneously active neurones in the nucleus reticularis thalami and underlying ventrobasal complex.

2. The initial response to MRF stimulation of 90% of the ACh‐inhibited neurones found in the region of the dorsolateral nucleus reticularis was an inhibition. Conversely, the initial response of 82% of the ACh‐excited neurones in the ventrobasal complex was an excitation. Neurones in the rostral pole of the nucleus reticularis were inhibited by both ACh and RMF stimulation.

3. The mean latency (and
s.e. of mean) for the MRF‐evoked inhibition was 13·7 ± 3·2 ms (n = 42) and that for the MRF‐evoked excitation, 44.1 ± 4.2 ms (n = 35).

4. The ACh‐evoked inhibitions were blocked by iontophoretic atropine, in doses that did not block amino acid‐evoked inhibition. In twenty‐four ACh‐inhibited neurones the effect of iontophoretic atropine was tested on MRF‐evoked inhibition. In all twenty‐four neurones atropine had no effect on the early phase of MRF‐evoked inhibition but weakly antagonized the late phase of inhibition in nine of fourteen neurones.

5. Interspike‐interval histograms showed that the firing pattern of neurones in the nucleus reticularis was characterized by periods of prolonged, high‐frequency bursting. Both the ACh‐evoked inhibitions and the late phase of MRF‐evoked inhibitions were accompanied by an increased burst activity. In contrast, iontophoretic atropine tended to suppress burst activity.

6. The possibility is discussed that electrical stimulation of the MRF activates an inhibitory cholinergic projection to the nucleus reticularis. Since neurones of the nucleus reticularis have been shown to inhibit thalamic relay cells, activation of this inhibitory pathway may play a role in MRF‐evoked facilitation of thalamo‐cortical relay transmission and the associated electrocortical desynchronization.
The effect of indomethacin on autoregulation of renal blood flow in the anasthetized dog.
Authors: Beilin L J , Bhattacharya J
Published: December 2014

1. Renal blood flow autoregulation was studied in anaesthetized greyhounds, using an electromagnetic flowmeter, before and after the administration of the prostaglandin‐synthesis inhibitor, indomethacin, or phosphate buffer. 2. Indomethacin caused a reduction in renal blood flow at all levels of perfusion pressure, but did not affect the ability of the kidney to autoregulate. 3. The aburpt reinstatement of renal perfusion pressure from previously reduced levels caused a triphasic transient response in flow. Peak hyperaemia at the beginning of the transient was not affected by indomethacin. After indomethacin, the second phase of this flow transient showed an oscillatory pattern during which flow fell initially to levels significantly lower than control. 4. It is concluded that although indomethacin did not abolish steady‐state autoregulation, renal prostaglandins may damp rapid oscillations in renal blood flow and thus contribute to the efficiency of autoregulation.
A long‐lasting potentiation of transmitter release related to an increase in transmitter stores in a sympathetic ganglion
Authors: Birks R. I.
Published: December 2014

1. High frequency preganglionic nerve stimulation increases the acetylcholine (ACh) stores of the cat superior cervical ganglion. The increase reaches a maximum 20 min following 60 min conditioning stimulation at 20/s. The effect of this conditioning on ACh release in ganglia perfused with plasma and test stimulated at 4 or 5/s has been studied, and the relationship of ACh stores to ACh release in conditioned ganglia determined.

2. The rate of ACh release in response to test stimulation at 5/s for 15 min, starting 20 min following conditioning, was 174% of the rate found in unconditioned ganglia. The ACh stores of the conditioned ganglia at the end of the test were calculated to be 173% of the control ganglion stores.

3. When test stimulation at 4/s was started 5 min following conditioning, the rate of ACh release showed a variable pattern of increase and decrease over a 75 min period. The mean peak rate of release was about 150% of the control rate, and the duration of potentiation was about 75 min.

4. When conditioned, unperfused ganglia were tested by stimulation at 4/s the ACh stores were found to increase and decrease in parallel with the increase and decrease in ACh release rates found in the perfusion experiments.

5. It was found also that the magnitude of the increase in ACh stores and ACh release was related to the amount of ACh in the ganglionic stores at the onset of conditioning, being greater for the ganglia with the smaller initial stores.

6. It is concluded that the potentiation of ACh release in ganglia conditioned in this way is directly related to the accompanying increase in ACh stores.

7. The possible significance of alterations of ACh stores and ACh release as a mechanism of modulatory control of ganglionic transmission is discussed.
Quantitative aspects of responses in trigeminal relay neurones and interneurones following mechanical stimulation of sinus hairs and skin in the cat
Authors: Gottschaldt K.-M. , Young D. W.
Published: December 2014

1. Stimulus‐response relationships in discharges of trigeminal relay‐ and interneurones were investigated in the barbiturate anaesthetized cat using controlled sinus hair or skin displacements.

2. In comparison with discharges in slowly adapting primary afferent fibres the responses in all higher order neurones were considerably reduced in firing rate and often revealed modifications suggesting the interaction of mechanisms actively modulating the afferent input.

3. In relay neurones with or without a tonic discharge component the ‘dynamic on’ response during a trapezoidal displacement of sinus hairs was found to be determined entirely or predominantly by the movement velocity and to be independent of the deflexion angle of a stimulus. In contrast, the static response in tonic relay neurones was determined by both the movement velocity and the displacement amplitude.

4. Spatial summation of afferent input caused either only quantitative changes in the responses of relay neurones leaving the general discharge properties unaltered or caused both qualitative and quantitative changes in the responses.

5. Interneurones consisted of two functional groups. In about 25% of them the responses were not or only slightly dependent on the intensity of the applied stimulus, often burstlike and of an all or nothing character. In the second group of interneurones the responses showed a quantitative dependence on the applied stimuli. In this group of interneurones responses often increased with the spatial extension of the peripheral stimulus revealing spatial summation of the afferent input.
The pH of brain extracellular fluid in the cat
Authors: Cragg Patricia , Patterson Lillian , Purves M. J.
Published: December 2014

1. The blood supply to the medulla was determined by the injection of indian ink via the vertebral arteries. Virtually the whole medulla was supplied by penetrating vessels from the ventral surface. The highest density of small arterioles and venules was found close to the roots of XII and on the ventrolateral surface.

2. The pH of extracellular fluid (pHe.c.f.) was measured with pH microelectrodes of tip size 1‐3 μm in cortex and medulla in seventeen cats, anaesthetized with pentobarbitone or a chloralose—urethane mixture. Parallel measurements were made of the pH of c.s.f. and plasma, the DC potential between plasma and brain and ventilation or phrenic nerve discharge.

3. In the majority of tests under steady conditions, the pH of e.c.f. was found to be lower than that of c.s.f. by between 0·03 and 0·08 units. No systematic pH gradients could be found to a depth of 5 mm beneath the surface of either medulla or cortex.

4. When plasma PCO2 was altered, pHe.c.f. changed with a latent period and speed of response related to the density of blood vessels. In vascular areas of the medulla and in the cortex, the latent period of 4 sec and the change of pHe.c.f. coincided with changes in ventilation. Changes in pHc.s.f. over the same areas were invariably slower.

5. CO2 buffering capacities were in the order plasma > e.c.f. > c.s.f. Typical values were respectively, ‐2·2, ‐2·1 and ‐1·6.

6. The pH of e.c.f. was unaffected by the intravenous injection of H+ and only slowly by the injection of HCO3‐. Only up to a depth of 1 mm beneath the surface was pHe.c.f. affected by superfusion of mock c.s.f. in the range 6·8‐8·0 units. This response had a latent period of 2‐3 min and was complete in 15 min.

7. The pH of e.c.f. fell with hypoxia after a latent period of > 1 min and if all vasosensory nerves had been cut, pHe.c.f. was markedly affected by changes of blood pressure.

8. These results indicate that even under steady conditions, the pH of e.c.f. and c.s.f. is not identical, that pHe.c.f. is more obviously affected by changes in Pa, CO2 than pHc.s.f. and that putative H+ sensors which drive respiratory neurones are likely to be similarly affected.
Changes in excitability of the cell membrane during 'differentiation without cleavage' in the egg of the annelid, Chaetopterus pergamentaceus.
Authors: Hagiwara S , Miyasaki S
Published: December 2014

1. The egg of the polychaete, Chaetopterus pergamentaceus, differentiates parthenogenetically without cleavage after 1 hr in a high K+ solution. The changes in the electrical properties of the membrane during differentiation have been investigated. 2. The treatment with the K solution for 40‐60 min made unfertilized eggs become amoeboid cells in 4‐5 hr and finally ciliated unicellular embryos in 14‐16 hr. 3. In the untreated egg the action potential is Ca dependent and no Na component is found. The steady‐state current‐voltage relation has a marked inward rectification and shows a less marked outward rectification. 4. There are no significant changes in these properties of the cell membrane immediately after 40‐60 min K treatment. 5. In the amoeboid cell stage (4‐5 hr) the outward rectification increases significantly. 6. In the ciliated unicellular embryo the action potential is Ca and Na dependent. 7. The result suggests that Ca channels are present in the egg initially, K channels appear next and Na channels appear later.
Synaptic actions of individual vestibular neurones on cat neck motoneurones
Authors: Rapoport S. , Susswein A. , Uchino Y. , Wilson V. J.
Published: December 2014

1. Unitary synaptic potentials evoked by the activity of single vestibulocollic neurones were recorded by means of spike‐triggered signal averaging in neck extensor motoneurones of decerebrate cats. Properties of the vestibulocollic neurones which produced the potentials were examined.

2. Vestibulocollic neurones were first identified as projecting to the C3 grey matter by antidromic microstimulation within the C3 extensor motoneurone pool. The spontaneous or glutamate‐driven activity of the vestibulocollic neurones was then used to trigger the averaging computer. In this way ten inhibitory and two excitatory neurones were identified (20% of neurones tested).

3. Action potentials in local branches of vestibulocollic neurones were usually recorded in the vicinity of motoneurones. Mean orthodromic conduction time from the foot of the extracellular spike, recorded in the vestibular nuclei, that triggered the averager was 0·72 msec. Mean synaptic delay was 0·4 msec.

4. I.p.s.p.s had a mean time to peak of 0·81 msec and were readily reversed by injection of hyperpolarizing current. These data, together with the shape indices of i.p.s.p.s indicate that they are generated proximally on motoneurones.

5. All vestibulocollic neurones making synapses with motoneurones were monosynaptically driven by stimulation of the ipsilateral vestibular nerve. Four out of seven tested were inhibited by stimulation of the contralateral vestibular nerve (commissural inhibition).

6. Two excitatory neurones were located in Deiters' nucleus or on the Deiters'‐descending border. Inhibitory neurones were found relatively medially in the vestibular complex in the medial, descending and Deiters' nuclei.

7. Vestibulocollic neurones acting on motoneurones were tested for axon branching to more caudal levels of the spinal cord with electrodes placed at C5‐7. Both of the excitatory and two out of nine inhibitory neurones branched.
The role of adrenergic receptor blockade in serotonin‐induced changes in the pulmonary circulation.
Authors: Rapaport E , Rolston W A , Stern S
Published: December 2014

1. In dogs i.v. injection of serotonin caused a rise in pulmonary artery pressure and pulmonary arteriocapillary resistance that persisted even after alpha‐ and beta‐adrenergic receptor blockade; pulmonary venous resistance also increased, but this was abolished by pretreatment with either propranolol or phenoxybenzamine. 2. The injection of serotonin into the ascending aorta produced an immediate rise in systemic, pulmonary arterial and pulmonary venous pressures and pulmonary venous resistance. After phenoxybenzmine, the rise in systemic and pulmonary arterial pressures remained unchanged, but previously observed increases in pulmonary venous pressure and resistance were blocked. In contrast, propranolol failed to abolish the rise in pulmonary venous resistance after serotonin injection into the ascending aorta. 3. These results confirm the observation that the vasoconstrictor effect attributed to intravenously injected serotonin on the arterial side of the pulmonary circulation is independent of the known sympathetic pathways. The data suggest that the pulmonary venoconstriction induced by intravenous serotonin is of reflex origin, abolished by alpha and beta receptor blockade, whereas the efferent arm of the reflex pulmonary venoconstriction following injection of serotonin into the ascending aorta is mediated via alpha‐adrenergic receptors.
Some electrical properties of the rabbit anococcygeus muscle and a comparison of the effects of inhibitory nerve stimulation in the rat and rabbit
Authors: Creed Kate E. , Gillespie J. S.
Published: December 2014

1. Simultaneous recordings of mechanical activity and membrane potential of individual smooth muscle cells have been made in the rabbit anococcygeus muscle and the effect of field stimulation on these examined.

2. In the absence of tone the mean resting membrane potential was ‐ 48 mV. In the stretched muscle spontaneous tone and rhythmic activity quite frequently appeared and this was associated with depolarization of the muscle cells.

3. The response to field stimulation depended on the frequency of stimulation, the level of membrane potential and the presence of myogenic tone. The usual response to single pulses or low frequency stimulation was a hyperpolarization of up to 30 mV (mean 14±6·8 mV) after a latency of 185 msec and accompanied by muscle relaxation. Higher frequencies (over 8 Hz) produced an initial depolarization often with a spike potential and followed by hyperpolarization. The mechanical response in these instances was contraction or contraction followed by relaxation. At all frequencies rebound depolarization and an associated contraction followed the end of stimulation).

4. Phentolamine (5×10−6
M) and guanethidine (10−6
M) blocked the initial depolarization and contraction but had no effect on hyperpolarization, muscle relaxation or rebound depolarization and contraction.

5. The effect of field stimulation in the presence of guanethidine (4×10−5
M) was re‐examined in the rat anococcygeus. Single pulses were ineffective, repetitive stimulation produced muscle relaxation but no hyperpolarization comparable to the rabbit. Any oscillations in membrane potential were damped during field stimulation and sometimes a small hyperpolarization was produced with a maximum amplitude of 13 mV and a mean of 1·9±1·2 mV.

6. The transmembrane potential at the peak of hyperpolarization in the rabbit was rarely more than ‐70 mV. Passive displacement of the membrane potential by current pulses altered the amplitude of the hyperpolarization and suggested that there was a reversal potential at between ‐80 and ‐90 mV.

7. No change in input resistance could be measured during inhibitory nerve stimulation in either the rabbit or the rat but measurements based on electrotonic potentials indicated a reducation in membrane resistance, small in the rat but greater in the rabbit.

8. These experiments suggest that in both species muscle relaxation is associated with an increase in ionic permeability and a move, at least in the rabbit muscle, towards an equilibrium potential of ‐80 to ‐90 mV. In view of the much smaller effect in the rat it is not clear whether this is the cause or at least the sole cause of the muscle relaxation.
Voltage sensitive calcium channels in the presynaptic terminals of a decrementally conducting photoreceptor
Authors: Ross W. N. , Stuart Ann E.
Published: December 2014

1. Intracellular recordings were made from the presynaptic regions of the photoreceptors of the median ocellus of the giant barnacle, Balanus nubilus.

2. Millivolt changes in membrane potential near the dark resting level in the terminals elicit post‐synaptic activity and consequently must be sufficient to modulate transmitter release from these endings.

3. In normal saline the terminal voltage usually changes in a graded manner to increasing intensities of illumination of the cell. When the terminal region is superfused with saline containing TEA, 3‐AP or high concentrations of K, an all‐or‐none action potential can be elicited consistently by light or injected current.

4. The peak value of this action potential depends on the Ca concentration in the saline. The action potential can be generated if Sr or Ba ions replace Ca, but is reduced or blocked if Mg, Co, or Mn ions are added to the saline. It is virtually unaffected by TTX or replacement of Na with TMA ions in the saline. These results suggest that Ca carries most or all of the inward current during the action potential.

5. The action potential is followed by a large undershoot which can last several seconds. The amplitude and duration of the action potential and the duration of the undershoot all grow in increasing concentrations of TEA up to 400 m
M, the highest concentration tested. The threshold for the action potential decreases as the concentration of TEA is increased to 10 m
M; increasing the concentration further has no effect on the threshold. These observations suggest that TEA blocks a voltage‐sensitive potassium conductance at low concentrations but has less effect on the current responsible for the undershoot.

6. Electrophysiological and pharmacological evidence suggests that the Ca channels are concentrated in the presynaptic terminals of this photoreceptor.
Formation and elimination of foreign synapses on adult salamander muscle
Authors: Dennis M. J. , Yip J. W.
Published: December 2014

1. Synapses by flexor nerve were induced on denervated extensor muscle in adult salamander forelimbs. Excitatory potentials evoked by these ‘foreign’ synapses were at first small but increased to normal amplitude within several weeks, in the absence of correct nerve reinnervation.

2. Upon return of the correct nerve the efficacy of foreign synaptic transmission began to decline. The time of initiation of this decline correlated well with the resumption of correct nerve transmission. The suppression of foreign transmission involved a reduction in mean quantal content of transmitter release.

3. Suppression of foreign synapses was sufficiently thorough that most ceased transmitting entirely. Before reinnervation by the correct nerve 97% of the extensor muscle fibres received functional foreign synapses while 4‐6 months after correct nerve return only 35% of the fibres retained foreign synapses, with weak transmission.

4. Two lines of evidence indicate that suppressed foreign synapses are lost from the muscle: (a) a second correct nerve lesion 6‐8 months after the initial denervation produced no significant increase in the proportion of fibres with foreign transmission and (b) four muscles which showed complete suppression of foreign transmission were bathed in medium containing horseradish peroxidase (h.r.p.) and the correct nerve was stimulated repetitively. Subsequent histochemical staining for h.r.p. and examination of synapses by electron microscopy revealed that 94% of the axon terminals had h.r.p. incorporated in vesicles. Thus at least that percentage of all identifiable synapses were from the correct nerve.

5. This ability to eliminate incorrect synapses in favour of correct ones is speculated to be a general characteristic of embryonic nervous systems, which in adulthood is retained by salamanders but lost by most other animals.
Lability of renal papillary tissue composition in the rat.
Authors: Atherton J C
Published: December 2014

1. The acute effects of (a) a minor operative procedure using ether as the anaesthetic, and (b) the administration of 0.9% saline as a single I.V. injection in the conscious rat, on renal tissue composition were studied in hydropenic and normally hydrated rats. 2. The operative procedure and anaesthesia induced a rapid and transient decrease in papillary osmolality in both hydropenic and normally hydrated animals, the important contributing factor being a significant decrease in urea content. 3. Administration of a small volume of saline caused a rapid decrease in urea content, and an increase in water content. 4. It is concluded that papillary composition is extremely labile, large changes being produced by relatively minor experimental procedures.
The effect of disuse on cholinergic enzymes.
Authors: Butler I J , Drachman D B , Goldberg A M
Published: December 2014

1. The effects of disuse on the activity of choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) have been investigated in the sciatic nerve and leg muscles of the rat. 2. Disuse was produced by blockade of nerve conduction by repeated subperineurial injection of tetrodotoxin (TTX), and the effects were compared to those of denervation. 3. After 8 days of disuse there was no change in neural ChAT activity in the sciatic nerves, anterior roots or intramuscular terminals. By contrast, surgical section of the sciatic nerve resulted in a marked decrease of ChAT in the nerve terminals. 4. Similarly, after 8 days of disuse there was no change in neural AChE activity in the sciatic nerves or anterior roots. 5. AChE activity in the disused muscles decreased by more than 50%, which was comparable to the effect of surgical denervation. 6. These results indicate that disuse produced by TTX blockade of nerve conduction does not affect the cholinergic enzymes ChAT and AChE in nerves, but does lead to a significant decrease in muscle AChE.
Action of fatty acids on the exocrine pancreatic secretion of the conscious rat: further evidence for a protein pancreatic inhibitory factor.
Authors: Demol P , Sarles H
Published: December 2014

The existence of a delayed inhibition of the secretion of protein by the rat pancreas after intraduodenal injection of oleic acid has been confirmed. 1. This phenomenon is not dependent on the presence or absence of bile or pancreatic juice in the intestine. 2. The action of oleic acid is not a pathological phenomenon due to lesions of the gut mucosa because isotonic solutions of Na oleate dispersed into polysorbate 80 or olive oil (rich in oleic acid) plus pancreatic juice have the same effect. 3. Fatty acids must be free or saponified but not esterified in the form of triglycerides. Triglycerides are only effective if pancreatic juice is simultaneously reintroduced into the duodenum. 4. Oleic acid (C18 monoéne) is more efficient than caprylic acid (C8) and butyric acid (C4) is ineffective. The effect of chain length in releasing the inhibitory factor is therefore approximately the same as in CCK‐PZ release. 5. Intraduodenal infusion of hypertonic glucose solution does not inhibit pancreatic protein secretion indicating that release of enteroglucagon is probably not responsible for the inhibition. The inhibitory action of hypertonic NaCl solution is not explained.
The synaptic connexions to intercostal motoneurones as revealed by the average common excitation potential.
Authors: Kirkwood P A , Sears T A
Published: December 2014

1. The hypothesis is advanced that the joint occurrence of unitary e.p.s.p.s evoked in motoneurones by branches of common stem presynaptic fibres causes, on average, transient depolarization in one motoneurone at the time of discharge in another motoneurone of the same pool. 2. The hypothesis was tested in anaesthetized, paralysed cats by averaging the naturally occurring synpatic noise of thoracic inspiratory motoneurones with an averager triggered by spikes from other inspiratory motoneurones. These spikes were obtained as efferent discharges in nerve filaments supplying the proximal regions of the external intercostal muscles. 3. A transient depolarization centred around the time of the trigger spikes was consistently observed and was designated the average common excitation (a.c.e.) potential. 4. The peak depolarization lay between ‐1.0 and +4.6 msec (mean +0.7 msec) with respect to the trigger spikes and the rise times of its most prominent component ranged from 4 to 16 msec (mean 8.4 msec). 5. The amplitudes of the a.c.e. potentials ranged from 6 to 104 muV (mean 32 muV) when the trigger spikes were derived from a filament in the same segment as the relevant motoneurones, and from 3 to 42 muV (mean 19 muV) when the filament was two segments rostral to the motoneurone. 6. Cells innervating the proximal region of the intercostal space gave larger a.c.e. potentials than those innervating more distal regions and also showed larger central respiratory drive potentials. 7. A.c.e. potentials were observed for either alpha or gamma spikes as triggers. The potentials were usually smaller for the gamma than for the alpha spikes, the mean ration being about 0.6. The presence of the a.c.e. potentials from the gamma spikes was taken as evidence for alpha‐gamma coactivation by common presynaptic axons. 8. A theory is developed which quantitatively accounts for the main features of both the a.c.e. potential and the short term synchrony observed by Sears & Stagg (1976). 9. The theory includes the proposition that the raised probability of firing of a motoneurone due to a unitary e.p.s.p. has a time course which may be described by the sum of the e.p.s.p. time course and its time differential. Thus, via the measurements, the theory predicts at least to a first approximation the expected probability of firing due to e.p.s.p.s of various shapes and sizes.
Identification of intrafusal muscle fibres activated by single fusimotor axons and injected with fluorescent dye in cat tenuissimus spindles.
Authors: Barker D , Bessou P , Jankowska E , Pagès B , Stacey M J
Published: December 2014

1. Intrafusal muscle fibres of cat tenuissimus spindles have been injected with the fluorescent dye Procion Yellow and identified histologically after recording their changes in membrane potential during 1/sec stimulation of single static or dynamic gamma axons. 2. Thirteen intrafusal muscle fibres innervated by static gamma axons were identified as eight bag2 and five chain fibres. The fact that none proved to be a bag1 fibre is not regarded as significant, for reasons given in the Discussion. 3. In one spindle Procion Yellow was injected into two intrafusal muscle fibres activated by the same static gamma axon; they were identified as a bag2 and a chain fibre. 4. Nine intrafusal muscle fibres innervated by dynamic gamma axons were identified as seven bag1 fibres, one bag2 fibre, and one long chain fibre. 5. In one spindle two bag fibres were injected, one activated by a dynamic gamma axon, the other by a static gamma axon; the former proved to be a bag1 fibre, the latter a bag2 fibre. 6. Stimulation of static gamma axons elicited junctional potentials in seven bag2 fibres and one damaged chain fibre, and action potentials in one bag2 and four chain fibres. In the whole sample of impaled intrafusal muscle fibres (identified and unidentified) activated by static axons, junctional potentials were recorded from twenty‐three (62.2%), and action potentials from fourteen (37.8%). Stimulation of dynamic gamma axons always elicited junctional potentials. 7. In a number of instances it was possible to examine the ultrastructure of motor endings belonging to the stimulated gamma axon. The myoneural junctions of trail endings supplied by static gamma axons to bag2 and chain fibres were both smooth and folded; the deepest and most regular folding occurred on chain fibres. The terminals of p2 plates supplied to bag1 fibres by dynamic gamma axons had smooth myoneural junctions.
Exchange of 5‐hydroxyindoleacetic acid between the spinal cord and lumbar cerebrospinal fluid.
Authors: Bulat M , Zivković B
Published: December 2014

1. After inhibition of 5‐hydroxyindoleacetic acid (5‐HIAA) transport by repeated administration of probenecid in cats, this acid accumulates linearly in the lumbosacral cord, lumbar cerebrospinal fluid (c.s.f.) and cisternal fluid during 5 hr of experiment. 2. A simple mathematical analysis of these results shows that (a) the rates of 5‐HIAA accumulation in the lumbar c.s.f. and cisternal c.s.f. are faster than in the cord, (b) about 22% of 5‐HIAA formed in the cord diffuses into lumbar c.s.f. and (c) by measuring 5‐HIAA in the lumbar c.s.f. the concentration and turnover of 5‐HIAA and turnover of serotonin in the lumbosacral cord can be calculated as well as the changes of 5‐HIAA in the cisternal c.s.f. predicted. 3. These results suggest that it is possible to calculate the level and turnover of endogenous substances in the central nervous system on the basis of their measurement in the c.s.f.
Effects of glucose on water and sodium reabsorption in the proximal convoluted tubule of rat kidney.
Authors: Bishop J H , Green R , Thomas S
Published: December 2014

1. The effects of glucose on sodium and water reabsorption by rat renal proximal tubules was investigated by in situ microperfusion of segments of proximal tubules with solutions containing glucose or no glucose, with and without phlorizin. 2. Absence of glucose did not significantly alter net water flux. Sodium flux was reduced by about 10% but this was not statistically significant. 3. In the absence of glucose in the perfusion fluid net secretion of glucose occurred. 4. Phlorizin reduced either net reabsorption or net secretion of glucose; and net water flux. 5. The data suggest that in later parts of the proximal convoluted tubule some sodium may be co‐transported with glucose, but that this represents only a small fraction of the total sodium reabsorption. 6. It is suggested that the glucose carrier is reversible and in appropriate circumstances could cause glucose secretion. 7. Although phlorizin alters net water flux the underlying mechanisms are not clear. 8. The calculated osmolality of the reabsorbate was significantly greater than the perfusate osmolality and greater than plasma osmolality although this was not quite significant statistically.
A barbiturate induced intensification of the inhibitory potential in slices of guinea‐pig olfactory cortex.
Authors: Scholfield C N
Published: December 2014

1. A study has been made of the effect of barbiturates on membrane constants and synaptic potentials of neurones in the isolated guinea‐pig olfactory cortex slice. 2. Normally, a long depolarizing i.p.s.p. follows the e.p.s.p. Pentobarbitone (0.1 mM) produced a tenfold increase in the duration of the high conductance phase of this i.p.s.p. 3. The i.p.s.p. was potentiated increasingly with higher barbiturate concentrations from 0.02 to 1.0 mM‐pentobarbitone and 0.2 to 5 mM‐phenobarbitone. 4. The resting membrane conductance, the initial phase of the e.p.s.p. and the threshold for the action potential were unaffected at lower concentrations. 5. The highest barbiturate doses increased the resting membrane conductance. This was associated with a depolarization of about 14 mV maximally and resulted in smaller synaptic potentials. The effect was probably generated by the same mechanism as the i.p.s.p. 6. This fortifies the idea that barbiturates have a primary action on prolonging inhibition rather than a depression in the excitatory potential.
Blocking of the squid axon potassium channel by external caesium ions.
Authors: Adelman W J , French R J
Published: December 2014

1. The blocking by external Cs of inward tail currents though the K channel of the squid giant axon, as seen by the effect of Cs on the 'instantaneous' I‐V curve is described. 2. Block onset is complete within 50‐‐100 musec of a step in voltage. The block produces a negative slope region in the inward current quadrants of the I‐V plots. 3. The experiments were performed in the presence of external concentrations of 240 mM‐K and 0‐200 mM‐Cs, with the external ionic strength maintained by substituting Tris or Na for the Cs. Essentially the same results were obtained with either Tris or Na as the substitute ion. 4. The concentration of Cs required to block 50% of the K channels at zero transmembrane voltage, in intact axons, was estimated to be approximately 1 M. 5. The slope of the dose‐response curve is steeper than expected for a blocking reaction with 1:1 stoichiometry when membrane voltage is in the neighbourhood of 100 mV. 6. With Cs concentrations greater than or approximately 50 mM, the voltage dependence of the block is too steep to be accounted for by the binding of a single Cs ion per channel within the membrane electric field. 7. In perfused axons, the block occurred at less negative internal voltage when internal K concentration was reduced. 8. These observations are qualitatively consistent with a multisite channel showing single file properties.
The dependence of membrane potential on extracellular chloride concentration in mammalian skeletal muscle fibres.
Authors: Dulhunty A F
Published: December 2014

1. The steady‐state intracellular membrane potential of fibres in thin bundles dissected from mouse extensor digitorum longus or soleus muscles or rat sternomastoid muscles was measured with 3 M‐KCl glass micro‐electrodes. The steady‐state membrane potential was found to depend on the extracellular concentrations of Na, K and Cl ions. 2. The resting membrane potential (3.5 mM‐[K]o, 160 mM‐[Cl]o) was ‐74 +/‐ 1 mV (mean +/‐ S.E.) and a reduction in [Cl]o to 3.5 mM caused a reversible steady‐state hyperpolarization to ‐94 +/‐ 1 mV (mean +/‐ S.E.). 3. The steady‐state membrane potentials recorded in fibres exposed to different [K]o and zero [Cl]o were consistent with potentials predicted by the Goldman, Hodgkin & Katz (GHK) equation for Na and K. The results of similar experiments done with Cl as the major external anion could not be fitted by the same equation. 4. The GHK equation for Na, K and Cl did fit data obtained from fibres in solutions containing different [K]o with Cl as the major external anion if the intracellular Cl concentration was allowed to be out of equilibrium with the steady‐state membrane potential. 5. It is suggested that an active influx of Cl ions controls the intracellular Cl concentrations in these fibres and hence maintains the Cl equilibrium potential at a depolarized value with respect to the resting membrane potential. 6. The steady‐state membrane potential of rat diaphragm fibres was independent of [Cl]o and it seems likely that the intracellular Cl concentration of these fibres is not controlled by active Cl transport.