bluuebunny/crossref_metadata_2025 huggingface dataset:
Dopamine, noradrenaline and isoprenaline: secretory and electrophysiological effects in vitro on mouse pancreas.
Authors: Berger Z , Laugier R
Published: December 2014

The amylase release from mouse pancreatic fragments was studied after dopamine (DA), and alpha‐ or beta‐sympathomimetic agonist application. The electrical parameters of the acinar cell membrane were also monitored. Both DA (from 5 X 10(‐6) to 10(‐4) M) and beta‐stimulants (isoprenaline from 5 X 10(‐6) to 5 X 10(‐5) M; noradrenaline from 3 X 10(‐4) to 10(‐3) M) evoked an increase in amylase release, while noradrenaline in alpha‐receptor stimulating doses failed to have any effect. The stimulatory effect of DA was blocked by ganglion blockers (Arfonad 10(‐5) M; pentamethonium 3 X 10(‐5) M) in a competitive manner and a dual antagonism was observed with atropine (10(‐7) M, 10(‐9) M). An alpha‐receptor antagonist (phentolamine 10(‐5) M) and a beta‐receptor antagonist (propranolol 10(‐5) M) had no influence on the dopamine response. Moreover, the DA‐induced stimulation was dependent on the presence of extracellular calcium. Perfusion with 10(‐4) and 10(‐3) M‐DA or local application (from 77 micrograms to 4.3 mg), resulted in marked membrane depolarization with diminution of the input resistance. This effect was blocked by atropine (10(‐5) M) and pentamethonium (10(‐4) M), but not by propranolol (10(‐5) M) or phentolamine (10(‐5) M). The isoprenaline‐ (IP) and noradrenaline‐ (NA) induced increase in amylase release was competitively blocked by propranolol (10(‐5) M) but not by phentolamine (10(‐5) M). Atropine caused a dose‐dependent (10(‐7) M, 10(‐6) M) decrease in the maximal response (non‐competitive antagonism), while the ganglion blocker pentamethonium (10(‐4) M) was without effect. NA caused membrane depolarization accompanied by a decrease in the input resistance after local application (from 77 micrograms to 1.6 mg). This effect persisted in the presence of 10(‐5) M‐phentolamine but was abolished by 10(‐5) M‐propranolol. IP perfusion (10(‐4) and 10(‐3) M) or local application (0.3 M; from 32 to 130 micrograms) caused the same electrical changes as those induced by NA and DA. The effect of IP persisted in the presence of 10(‐5) M‐phentolamine, 10(‐4) M‐pentamethonium and 10(‐4) M‐domperidone, but was abolished by propranolol (10(‐5) M) and tetrodotoxin (5 X 10(‐6) M) and markedly diminished by atropine (10(‐5) M).(ABSTRACT TRUNCATED AT 400 WORDS)
Effects of apomorphine and haloperidol in fetal lambs.
Authors: Bamford O S , Dawes G S , Ward R A
Published: December 2014

Injections of 100 micrograms apomorphine (I.A.) in intact unanaesthetized fetal lambs resulted in the onset of low‐voltage electrocortical activity if not already present, onset or an increase in amplitude of fetal breathing movements, and in about 50% of experiments, onset or an increase in skeletal muscle activity. These responses also occurred during isocapnic hypoxia, though the stimulation of breathing was less than in normoxic lambs. Apomorphine had no consistent effects on the blood gases, pH, heart rate or blood pressure. In fetal lambs with the carotid nerves and vago‐sympathetic trunks sectioned, apomorphine had the same effects as in intact lambs, except that there was a small fall in arterial O2 pressure (Pa,O2). Haloperidol (0.5‐1 mg I.V.) had no effect on spontaneous breathing movements or electrocortical activity, but blocked all responses to apomorphine for several hours. Dopamine (up to 4 mg I.V.) caused an increase in arterial pressure accompanied by bradycardia, but had no effect on breathing movements or electrocortical activity. After suprapontine brain‐stem transection, the electrocortical response to apomorphine was reduced. The respiratory response was lost or reversed, with apomorphine causing a reduction in amplitude of breathing. Haloperidol reduced the incidence of breathing movements for several hours in brain‐stem‐transected fetuses. We conclude that there is a central pathway, including at least one dopaminergic synapse and with components above the pons, which can stimulate fetal motor activity and breathing. It does not appear to be tonically active and its normal function is unknown.
Evidence for interneuronally mediated Ia excitatory effects to human quadriceps motoneurones.
Authors: Fournier E , Meunier S , Pierrot-Deseilligny E , Shindo M
Published: December 2014

The possibility was investigated that interneuronal pathways contribute to Ia excitation of quadriceps motoneurones in normal man. Two techniques were used: the indirect spatial facilitation technique for investigating summation of Ia excitatory effects in interneurones which may be interposed in pathways to quadriceps motoneurones; the post‐stimulus time histogram method for time course measurement of the firing probability of voluntarily activated motor units following femoral nerve stimulation. The spatial facilitation technique was applied while using the quadriceps H reflex to assess the excitability of the whole motoneurone pool: the comparison was made between the excitatory effects of two conditioning stimuli applied either separately or together. Summation of effects at a premotoneuronal level is suggested if facilitation of the reflex evoked on combined conditioning stimulation is larger than the algebraic sum of facilitations evoked by separate stimuli. Quadriceps tendon tap and electrical stimulations applied to either the femoral nerve or to two of its branches, the nerves to the vastus lateralis and vastus medialis muscles, were used as conditioning stimuli. Since these stimuli were very weak (their strength being about at the threshold for facilitation of the test reflex), it can be assumed that they activated predominantly Ia fibres. The facilitation of the quadriceps H reflex evoked on combined stimulation was significantly larger than the algebraic sum of facilitations evoked by separate stimuli. In many experiments, although conditioning stimuli did not evoke any reflex facilitation when applied alone, a significant facilitation appeared on combined stimulation. This 'extra' facilitation of the reflex on combined stimulation appeared with a central latency of 4‐5 ms. It is argued that the only mechanism compatible with such a latency is summation at a premotoneuronal level. Post‐stimulus time histograms (p.s.t.h.s) of voluntarily activated quadriceps motor units were made following femoral nerve stimulation. Stimulation was triggered at a fixed delay time after the activation of the motor unit. A special attempt was made to set this delay so that the motoneuronal after‐hyperpolarization following the spike would partially prevent the discharge evoked by a monosynaptic excitatory post‐synaptic potential (e.p.s.p.). At stimulus strengths near motor threshold, femoral nerve stimulation regularly evoked an early increase in firing probability of motor units with the same latency as the H reflex.(ABSTRACT TRUNCATED AT 400 WORDS)
The secondary spikes of climbing fibre responses recorded from Purkinje cell somata in cat cerebellum.
Authors: Campbell N C , Hesslow G
Published: December 2014

Extracellularly recorded climbing fibre responses in Purkinje cell somata in the cerebellar cortex were investigated in cats deeply anaesthetized with barbiturate. The effects on the amplitude of initial and secondary spikes of preceding climbing fibre activation, on‐beam parallel fibre activation and off‐beam parallel fibre activation were studied. When a climbing fibre response was preceded by climbing fibre activation there was a decrease in the amplitude of the initial spike of the second response at intervals up to 25 ms and little effect at longer intervals. Secondary spike amplitude was greatly increased at intervals up to 100 ms. When a complex spike was preceded by on‐beam parallel fibre activation there was a decrease in the initial spike amplitude at short intervals and an increase in the amplitude at long intervals. Secondary spike amplitude was increased up to 150 ms after an on‐beam parallel fibre volley. When a complex spike was preceded by off‐beam parallel fibre stimulation there was an increase in initial spike amplitude at intervals up to about 200 ms and a decrease in secondary spike amplitude at intervals up to about 150 ms. The results show that the amplitude of the secondary spikes can be modified by a preceding input to the Purkinje cell. The results also suggest that the secondary spikes are generated in the Purkinje cell dendrites and the initial spike in the soma.
Intracellular tetraethylammonium ions enhance group Ia excitatory post‐synaptic potentials evoked in cat motoneurones.
Authors: Clements J D , Nelson P G , Redman S J
Published: December 2014

Single fibre group Ia excitatory post‐synaptic potentials (e.p.s.p.s) were recorded in cat spinal motoneurones after the neurones were injected with tetraethylammonium (TEA) ions. TEA injection increased the peak amplitude of most e.p.s.p.s. The time course of e.p.s.p.s generated at the soma was unaffected, but the time course of e.p.s.p.s generated in the dendrites was prolonged. The membrane time constant did not change after TEA injection. Somatic e.p.s.p.s were voltage clamped after TEA was injected. The reversal potential for these e.p.s.p.s was more positive than for e.p.s.p.s unaffected by TEA. Composite e.p.s.p.s added linearly, or greater than linearly, whereas in motoneurones without TEA they added linearly or less than linearly. The enhanced amplitude and prolonged time course observed in dendritic e.p.s.p.s after TEA injection was reduced by small hyperpolarizing currents. Greater than linear summation of composite e.p.s.p.s was converted to linear summation by small hyperpolarizing currents. The increase in somatic e.p.s.p.s was attributed to a more positive reversal potential for the e.p.s.p.s. We suggest that TEA decreases the relative permeability of K+ in the subsynaptic channels. We propose that in the presence of TEA, dendritic depolarization activates an inward current which amplifies and prolongs synaptic potentials spreading towards the soma.
The conductance and density of sodium channels in the cut‐open squid giant axon.
Authors: Bekkers J M , Greeff N G , Keynes R D
Published: December 2014

Non‐stationary Na current fluctuations in small voltage‐clamped patches of cut‐open squid giant axon were analysed by an ensemble‐average technique to yield the single Na channel conductance gamma Na and the Na channel density in the patch. gamma Na appeared to be voltage independent over the range ‐30 to +40 mV and had a mean value of 4.4 +/‐ 1.1 pS in 514 mM‐Na/20 mM‐Na at 5 kHz band width and temperature between 3.5 and 5.0 degrees C. gamma Na did not change significantly at band widths to 20 kHz. gamma Na in reduced Na solutions, 103 mM‐Na/4 mM‐Na, at 3.5‐5.0 degrees C had a mean value of 1.2 +/‐ 0.3 pS. Internal solutions containing 50 mM‐tetraethylammonium (TEA) depressed both gamma Na and the mean Na currents by roughly the same factor, compared with solutions without TEA. The reduced gamma Na had a mean value of 2.2 +/‐ 0.7 pS. The mean Na channel density in the standard 514 mM‐Na/20 mM‐Na solution was estimated to be 180 +/‐ 100 microM‐2. The densities in the other solutions mentioned above were not significantly different from this value.
Acid secretion through the Rana esculenta skin: involvement of an anion‐exchange mechanism at the basolateral membrane.
Authors: Duranti E , Ehrenfeld J , Harvey B J
Published: December 2014

Kinetic and electrophysiological studies were carried out to characterize the efflux of HCO3‐ (or OH‐) across the basolateral membrane of the proton‐secreting cells of the frog skin epithelium bathed with dilute saline mucosal solutions. In control conditions, the acidification of the mucosal solution (JnH+) was correlated directly with serosal alkalinization. Cl‐ substitution in the serosal Ringer (by gluconate or methylsulphate ions) induced an inhibition of proton excretion (70% inhibition). Measurements of the basolateral membrane potential with conventional micro‐electrodes and of cell Cl‐ activity (aCli) and proton activity with double‐barrelled ion‐sensitive micro‐electrodes recorded a basolateral membrane depolarization of 5.1 +/‐ 0.7 mV (n = 12), a decrease in aCli from 14.5 +/‐ 1.6 mequiv l‐1 to 1.8 +/‐ 0.3 mequiv l‐1 (n = 12), and a cell pH increase from 7.18 +/‐ 0.04 to 7.32 +/‐ 0.06 (n = 12) after serosal Cl‐ replacement. 4,4'‐diisothiocyanostilbene‐2‐2'‐disulphonic acid (DIDS) (10(‐4) M) and meclofenamate (5 X 10(‐5) M) inhibit JHn+ by 34% and 53% respectively whereas bumetanide did not block JHn+. Depolarization of the basolateral membrane (2 mM‐Ba2+ addition to the serosal solution) did not block proton excretion. We show that cell Cl‐ activity is maintained at a higher level than that predicted by the equilibrium potential, by a mechanism located at the basolateral membrane of the epithelium since the apical solution was Cl(‐)‐free. This mechanism is not sensitive to potential changes at the basolateral membrane in the range tested. An electroneutral Cl(‐)‐HCO3‐ exchange mechanism is the simplest hypothesis which can account for our results.
Secretion control for active and inactive renin: effect of ouabain on release from rabbit kidney cortex slices.
Authors: Ginesi L M , Noble A R
Published: December 2014

Release of active and inactive renin by rabbit kidney cortex slices was investigated. Inactive renin was estimated as the increase in renin activity after acidification (pH 2.8) of slice supernatant solutions. For kidney slices incubated in complete Krebs bicarbonate buffer, the Na‐K‐ATPase inhibitor ouabain (100 microM) reduced the secretion of both active (‐19.2%) and inactive (‐78.9%) forms of renin. In low Na buffers ([Na+] = 23 mM) active renin release was increased and inactive renin was suppressed. Both of these changes were abolished by addition of ouabain (100 microM). The reduction in inactive renin secretion produced by ouabain in complete Krebs buffer did not occur in low [Na+] buffers. In zero Ca2+ buffers containing EGTA (5 mM), secretion of both active and inactive renin was increased but these changes were abolished by addition of ouabain (100 microM). Incubating kidney slices in low Na+, zero Ca2+ media revealed differences between the secretion control mechanisms for the two forms of renin. The separate stimulatory effects of low Na+ and low Ca2+ were not additive for the release of active renin and inclusion of ouabain resulted in similar secretion rates to those under control conditions. For inactive renin secretion, in the absence of Ca2+ release mechanisms still respond to reduction in Na+ with decreased secretion. Conversely, in low Na+ buffers, removal of Ca2+ still promotes inactive renin secretion. These changes were abolished by the addition of ouabain (100 microM). Slices did not change in weight during incubation in media which did not contain ouabain. Addition of this inhibitor to control buffers and low Na buffers did result in an increase in weight. This correlated with the presence of Ca2+ in the buffer and did not appear to be related to [Na+]. These studies again show that the mechanisms regulating the secretion of active and inactive renin are not identical and support the hypothesis that Na+ have differing roles to play in the regulation of these two forms of renin.
Activation of acetylcholine receptor channels by covalently bound agonists in cultured rat myoballs.
Authors: Chabala L D , Lester H A
Published: December 2014

Kinetic and equilibrium aspects of receptor activation by two irreversibly bound ('tethered') agonists, QBr and bromoacetylcholine (BrACh), were examined in cultured embryonic rat muscle. Myoballs were treated with dithiothretitol (2 mM), washed, exposed to BrACh or QBr, and then washed again. Voltage‐clamp recordings were made both in the whole‐cell mode and with excised outside‐out patches at 15 degrees C. Whole‐cell voltage‐jump relaxations resembled those observed with reversibly bound agonists. The relaxation time constants were 5 ms for tethered QBr and 10 ms for tethered BrACh (‐100 mV, 15 degrees C). At more positive membrane potentials, the relaxation rate constants increased and the conductance decreased. Whole‐cell light‐flash relaxations with tethered QBr were also studied. The conductance was increased and decreased, respectively, by cis‐‐‐‐trans and trans‐‐‐‐cis photoisomerizations. The relaxation time constants equalled those for voltage jumps. The functional stoicheiometry of tethered QBr was investigated by studying the relaxations in response to light flashes that produced known changes in the mole fractions of the two isomers. It is concluded that the open state of each receptor channel is controlled by the isomeric state of a single tethered QBr molecule. In single‐channel recordings, tethered agonists opened channels with the same conductance as reversibly bound agonists (30 pS at 15 degrees C and ‐100 mV). More than 80% of the conductance was contributed by a population of openings with an average burst duration (lifetime) of 5 ms for QBr and 10 ms for BrACh. Thus the single‐channel and macroscopic currents seem to be dominated by the same type of channel; these are presumably monoliganded receptors. About 30% of the openings belonged to a population with an average lifetime of about 0.5 ms. This population contributed less than 5% of the conductance. There were also more long openings (greater than 50 ms) than expected from a simple exponential distribution. A few patches from BrACh‐treated cells showed openings with a conductance of 45 pS (‐100 mV) and an average duration of approximately 2 ms. These data allow one to assess whether the agonist‐receptor binding step plays a role in generating the brief openings. The main population of openings (burst durations 5 ms with QBr and 10 ms with BrACh) seem to be contributed by monoliganded receptors. One can therefore rule out the hypothesis that the brief channels arise exclusively from mono‐ and biliganded receptors, respectively.
Renal vasoconstrictor response to hypertonic saline in the dog: effects of prostaglandins, indomethacin and theophylline.
Authors: Gerber J G , Nies A S
Published: December 2014

The role of prostaglandins in the mechanism of the tubuloglomerular feed‐back was examined in the anaesthetized dog using the infusion of hypertonic saline to increase renal plasma sodium concentration by 30 mmol/l as the stimulus to activate the tubuloglomerular feed‐back. Two sequential infusions of hypertonic saline into the renal artery for 10 min separated by 90 min resulted in equivalent reductions in renal blood flow (264 +/‐ 32 to 174 +/‐ 20 ml/min first time; 280 +/‐ 29 to 200 +/‐ 15 ml/min second time). Administration of indomethacin, 8 mg/kg, between the two infusions did not alter the renovascular response to hypertonic saline (319 +/‐ 26 to 226 +/‐ 35 ml/min vs. 288 +/‐ 32 to 202 +/‐ 24 ml/min). Infusion of either prostaglandin E2 (PGE2) or prostaglandin I2 (PGI2) during the second hypertonic saline infusion period also resulted in no change in the renovascular response (251 +/‐ 37 to 141 +/‐ 31 ml/min vs. 297 +/‐ 53 to 184 +/‐ 51 ml/min; and 223 +/‐ 31 to 162 +/‐ 35 ml/min vs. 254 +/‐ 33 to 186 +/‐ 39 ml/min, respectively). Intrarenal theophylline, to a concentration of 40 micrograms/ml, however, totally abolished the renovascular response to hypertonic saline (279 +/‐ 20 to 209 +/‐ 13 ml/min control vs. 390 +/‐ 26 to 402 +/‐ 17 ml/min during theophylline). The systemic hypertensive response during the infusion of hypertonic saline was unaltered by indomethacin or prostaglandins but was totally abolished by theophylline.(ABSTRACT TRUNCATED AT 250 WORDS)
Quantal analysis of action of hemicholinium‐3 studied at a central cholinergic synapse of Aplysia.
Authors: Baux G , Poulain B , Tauc L
Published: December 2014

The effects of hemicholinium‐3 (HC‐3) on cholinergic transmission were studied on central identified inhibitory (H‐type post‐synaptic cell, Cl‐ channels) and on excitatory (D‐type post‐synaptic cell, cationic channels) synapses of Aplysia californica. In the H‐type post‐synaptic cell, the amplitude and the decay time of miniature post‐synaptic currents (m.p.s.c.s.) were calculated by statistical analysis of long duration induced post‐synaptic current (l.d.i.p.s.c.) due to 3 s depolarizations of the presynaptic neurone in the presence of tetrodotoxin. On H‐type receptors, with respect to acetylcholine (ACh), HC‐3 acted as an agonist and a blocker whereas on D‐type receptors, it acted only as a blocker. At low concentration of bath‐applied HC‐3, in the H‐type synapse, the decay time of the evoked inhibitory post‐synaptic current (i.p.s.c.) as well as that of the m.p.s.c. was lengthened. These changes were rapidly reversible by wash. The decay time of excitatory post‐synaptic current (e.p.s.c.) at the D‐type synapse was not affected. On the inhibitory synapse, HC‐3 applied in the bath at the concentration of 10(‐5) M, reduced considerably the size of the m.p.s.c.s whereas the evoked i.p.s.c.s and the l.d.i.p.s.c.s were only slightly affected pointing to an increase of the quantal content of both responses. After wash, both i.p.s.c.s and l.d.i.p.s.c.s showed a clear facilitation which persisted for several tens of minutes. The presence of presynaptic receptors was considered. Similar facilitation of e.p.s.c.s by HC‐3 was observed at the D‐type synapse. The comparison of the degree of depression by HC‐3 of the m.p.s.c.s and of the responses to ionophoretically applied ACh, indicated that the size of the quantum was not changed. Intracellular injection of HC‐3 into the presynaptic neurone of the H‐type synapse led to a decrease of transmitter release which affected solely the quantal content of the responses. As the synaptic transmission could not be restored by injection of exogenous ACh into the presynaptic neurone, it was concluded that the depression of transmission was not due to a decrease of ACh synthesis.
Responses of phrenic motoneurones of the cat to stimulation of medullary raphe nuclei.
Authors: Lalley P M
Published: December 2014

Responses of phrenic motoneurones to stimulation of the three medullary raphe nuclei (raphe magnus (r. magnus), raphe obscurus (r. obscurus) and raphe pallidus (r. pallidus] were recorded in anaesthetized and decerebrated cats. Stimulation of r. magnus or r. obscurus depressed phrenic motoneurones. Stimulation at 100 Hz reduced action potential frequency within each inspiratory burst, without appreciable changes in inspiratory duration, or number of inspiratory bursts per unit time. The depression was proportional to the stimulus intensity (40‐160 microA) and frequency (12‐100 Hz) and lasted throughout the period of stimulation. Intracellular recording revealed concomitant depression of central respiratory drive potentials (c.r.d.p.s) and increased membrane input resistance during r. obscurus or r. magnus stimulation. In motoneurones which discharged action potentials during expiratory as well as inspiratory phases following intracellular chloride injection, stimulation of r. magnus or r. obscurus depressed cell firing during both phases. Both c.r.d.p.s and reversed inhibitory post‐synaptic potentials (i.p.s.p.s) were depressed. These findings indicate that the depression is not related to post‐synaptic inhibition of phrenic motoneurones. Stimulation (100 Hz) of r. pallidus produced discharges of action potentials in phrenic motoneurones. Stimulation lengthened the duration of each inspiratory discharge in proportion to stimulus intensity. Continuous firing occurred throughout the period of stimulation with maximal intensities. Intracellular recordings revealed sustained depolarization and reduction in membrane input resistance during the discharge. Responses were recorded extracellularly from medullary inspiratory neurones of the dorsal respiratory group (d.r.g.) and ventral respiratory group (v.r.g.) and from vagal axons which fired in phase with phrenic nerve activity. Responses to raphe stimulation were similar to those recorded from phrenic motoneurones. Evidence is presented that the responses are not related to stimulation of decussating bulbo‐spinal axons from d.r.g. or v.r.g. neurones. It is suggested that medullary respiratory neurones receive inhibitory and excitatory synaptic inputs from medullary raphe neurones. Hypercapnia (5% CO2 in O2) or hypoxia (15% O2 in N2) reduced markedly the inhibition produced during stimulation of r. obscurus or r. magnus, and restored expiratory‐linked silent periods during stimulation of r. pallidus. Activation of Hering‐Breuer or baroreceptor reflexes did not alter responses to r. pallidus stimulation.(ABSTRACT TRUNCATED AT 400 WORDS)
Fluid and electrolyte handling in Long Evans and Brattleboro rats following injection of polyethylene glycol.
Authors: Bennett T , Gardiner S M
Published: December 2014

1. Intake and output of water, Na+ and K+ were measured in Long Evans and Brattleboro rats (deficient in hypothalamic and pituitary vasopressin) before and after subcutaneous injection of polyethylene glycol (PEG) sufficient to cause a substantial hypovolaemia. 2. In the Long Evans rats an initial fluid retention (due to oliguria and polydipsia) was accompanied by Na+ retention and K+ loss. On the second day there was a diuresis but Na+ retention persisted until days 3 and 4 when there was a natriuresis. 3. Brattleboro rats initially also showed fluid retention but this was achieved by hypodipsia with a greater oliguria; there was an accompanying retention of Na+ and K+. On the second day, a reduced fluid balance was still accompanied by Na+ retention but associated with kaliuresis. Diuresis and natriuresis occurred on the third day after PEG injection. 4. Thus, rats deficient in vasopressin respond to hypovolaemia by retaining fluid. The renal actions of aldosterone do not explain fully the changes in renal electrolyte handling.
Multiple receptor sites for a molluscan peptide (FMRFamide) and related peptides of Helix.
Authors: Cottrell G A , Davies N W
Published: December 2014

1. The membrane actions of some tetrapeptide amides and heptapeptide amides chemically related to the molluscan neuropeptides Phe‐Met‐Arg‐Phe‐NH2 (FMRFamide) and p‐Glu‐Asp‐Pro‐Phe‐Leu‐Arg‐Phe‐NH2 (pQDPFLRFamide) were tested and compared on identified neurones of Helix aspersa. 2. The C‐terminal sequence ‐Phe‐NH2 was an important requirement for each of the four different actions studied: slow increase in K conductance (gK), fast increase in gK, increase in Na conductance (gNa) and decrease in gK. 3. The response of some neurones involved a combination of such actions. 4. The tetrapeptide amides FMRFamide, Phe‐Leu‐Arg‐Phe‐NH2 (FLRFamide) and Phe‐Ile‐Arg‐Phe‐NH2 (FIRFamide) were more potent than the heptapeptide amides at producing the slow increase in gK and also produced the increase in gNa, not seen at all with the heptapeptide amides. 5. The heptapeptide amides induced the fast increase in gK which was not observed with the tetrapeptide amides. 6. Evidence is presented that each of the tetrapeptide amides tested acts on the same receptor type which mediates the increase in gNa and on which the heptapeptides were inactive. 7. The results are interpreted in terms of multiple receptors each of which however appears to require the C‐terminal sequence Phe‐Met(or Leu)‐Arg‐Phe‐NH2, as has been shown for some molluscan muscle preparations which react to these peptide amides (Price & Greenberg, 1980).
A comparison of sodium currents in rat and frog myelinated nerve: normal and modified sodium inactivation.
Authors: Neumcke B , Schwarz J R , Stämpfli R
Published: December 2014

1. Sodium currents were measured under voltage‐clamp conditions in Ranvier nodes of rat and frog nerve fibres at 20 degrees C. Voltage errors due to the resistance in series with the nodal membrane were minimized by reducing sodium currents with tetrodotoxin in the extracellular solutions. 2. The stationary and kinetic properties of sodium activation and inactivation were determined for a wide range of potentials (V) from ‐40 to 160 mV with respect to the initial holding level (V = 0 mV). 3. The curves m infinity(V) and h infinity(V) of stationary sodium activation and inactivation were not different in rat and frog fibres. 4. The time constants tau m, tau h of sodium activation and inactivation were normally larger in the rat than in the frog. At moderate depolarizations (0 less than or equal to V less than or equal to 80 mV) tau m in the rat was 15‐50% larger; the ratio of the rat to the frog tau h values was usually smaller. Thus tau m/tau h = 0.116 for the rat and 0.0965 for the frog at V = 60 mV (potential with maximum peak sodium inward current). 5. Sodium inactivation in rat nerve was slowed and became incomplete by application of intra‐axonal iodate or by treatment with external Anemonia toxin II (ATX II), chloramine‐T or Ruthenium Red. Peak sodium currents were not increased by these substances. 6. Wash‐out of ATX II from frog nerve was rapid and complete but partly irreversible in rat nerve. This suggests different properties or accessibilities of sodium channels in frog and rat nodes.
Fibre sizes and histochemical staining characteristics in normal and chronically stimulated fast muscle of cat.
Authors: Donselaar Y , Eerbeek O , Kernell D , Verhey B A
Published: December 2014

1. Normal and chronically stimulated peroneus longus muscles of the cat's hind limb were studied with respect to fibre size and staining properties for myofibrillar (myosin) adenosine triphosphatase (ATPase) and succinate dehydrogenase (SDH) activity. The intensity of staining for SDH activity was measured by microphotometry from the central portions of the muscle fibres ('core‐SDH staining'). For comparison, histochemical properties were also studied in non‐stimulated soleus muscles. 2. On account of the pH sensitivity of their myofibrillar ATPase, about 18% of the fibres in normal peroneus longus muscles were classified as type I, and about half of the remainder as II A and II B respectively. 3. In the normal peroneus longus muscles, the mean diameter of single muscle fibres generally varied between about 25 and 75 micron, whereby the average size of type I less than type II. 4. In the normal peroneus longus muscles the staining intensity for core SDH varied over a wide range. The average heaviness of staining was clearly ranked in the order type I greater than type II A greater than type II B. 5. Chronic stimulation was given to the deafferented common peroneal nerve by aid of a portable and remotely controlled mini‐stimulator. The stimulation was delivered in 'tonic' patterns (greater than or equal to 50% of total time taken up by activity) of 'fast' (20 or 40 Hz) or 'slow' (5 or 10 Hz) rates. 6. Prior to the period of long‐term stimulation, the cats had been subjected to a dorsal rhizotomy and hemispinalization on the ipsilateral (left) side. In the absence of chronic stimulation, these operations had no evident effects on the sizes or staining properties of peroneus longus fibres. 7. After 8 weeks of treatment with tonic patterns of stimulation, the fibres of peroneus longus muscles clearly became more similar to each other with respect to their diameter as well as their staining for ATPase and SDH activity. With respect to ATPase staining, however, the chronically stimulated peroneus longus fibres had become more similar to non‐stimulated soleus fibres than to non‐stimulated type I fibres of peroneus longus. With respect to the staining for core SDH, the chronically stimulated fibres all became similar to normal II A fibres of peroneus longus. The 'fast' and 'slow' patterns of chronic stimulation had the same effects on the staining properties. 8. Chronically stimulated peroneus longus muscles showed a decrease in fibre diameter which corresponded, roughly, to the concomitant decrease in muscle weight.(ABSTRACT TRUNCATED AT 400 WORDS)
Actions of trains and pairs of impulses from single primary afferent fibres on single spinocervical tract cells in cat.
Authors: Brown A G , Koerber H R , Noble R
Published: December 2014

1. In cats under chloralose anaesthesia single lumbosacral dorsal root ganglion cells of hair follicle afferent fibres were stimulated intracellularly to produce trains or pairs of impulses. At the same time, single spinocervical tract (s.c.t.) neurones were recorded extracellularly, from their axons in the upper lumbar spinal cord. Afferent fibre‐neurone pairs were chosen in which the receptive field of the fibre was contained within the excitatory receptive field (firing zone) of the neurone. 2. Trains of impulses of 2.0 Hz were less effective in increasing the probability of s.c.t. cell firing than trains at 0.67 Hz, and this latter rate was usually less effective than trains at 0.33 Hz. 3. Successive responses to individual members of a train of hair follicle afferent impulses were variable. In some pairs of units succeeding responses declined until a fairly consistent plateau was reached. In others there was no decline and the responses remained irregular. 4. Pairs or short trains of impulses revealed two phenomena: over the first 5 ms or so following an impulse in a group II hair follicle afferent fibre, a second or small group of impulses produced a greater response from the s.c.t. neurone but at intervals of 25‐200 ms there was a profound depression of the responses evoked by the second member of a pair of impulses. For A delta afferent fibres the early facilitation lasted for at least 25 ms. 5. It is concluded that a single impulse in a single hair follicle afferent fibre from within the excitatory receptive field of a s.c.t. neurone has complex actions on transmission through that neurone. An initial excitatory influence is followed by a long‐lasting depression that influences transmission through the system for at least 1500 ms. Possible mechanisms underlying this depression are discussed.
The effect of splanchnic nerve stimulation on adrenocortical activity in conscious calves.
Authors: Edwards A V , Jones C T
Published: December 2014

1. Right adrenal and various cardiovascular responses to stimulation of the peripheral end of the right splanchnic nerve have been investigated in the presence and absence of exogenous adrenocorticotrophin, ACTH1‐24, (5 ng min‐1 kg‐1). The adrenal‐clamp technique was employed in conscious calves in which the pituitary stalk had been cauterized 3‐4 days previously. 2. The I.V. infusion of ACTH1‐24 increased mean plasma ACTH concentration by about 1200 pg/ml and mean right adrenal cortisol output by about 500 ng min‐1 kg‐1. Stimulation of the peripheral end of the right splanchnic nerve at 4 Hz for 10 min produced a further rise in cortisol output, amounting to about 400 ng min‐1 kg‐1 (P less than 0.01). These changes in output were reflected accurately by changes in peripheral plasma cortisol concentration. 3. Closely similar amounts of adrenaline were released in response to splanchnic nerve stimulation in the presence and absence of exogenous ACTH. In the presence of ACTH the average mean output of noradrenaline (58 +/‐ 2 ng min‐1 kg‐1) was significantly less than that of adrenaline (102 +/‐ 4 ng min‐1 kg‐1; P less than 0.001), whereas the corresponding values were not significantly different in the absence of ACTH. 4. These results also confirm the fact that the fall in adrenal vascular resistance which occurs during splanchnic nerve stimulation is substantially reduced by ACTH, as is the rise in met5‐enkephalin output. 5. It is concluded that the splanchnic innervation is capable of enhancing the secretion of adrenal glucocorticoids in response to ACTH under physiological conditions in the conscious calf.
Slow membrane currents in bursting pace‐maker neurones of Tritonia.
Authors: Smith S J , Thompson S H
Published: December 2014

1. Membrane ionic currents in bursting pace‐maker neurones of the marine mollusc Tritonia were studied in voltage‐clamp experiments with emphasis on slow tail current relaxations after depolarizing pulses. 2. The slow tail current undergoes a complex transition from an initially inward current to an initially outward current as the duration of the depolarizing pulse is lengthened. It was found that the slow tail current is the sum of two separate and independent ionic currents. Methods were devised to study each current in isolation. 3. A slow inward tail current, termed IB, is activated by depolarization and decays exponentially on return to ‐55 mV with a time constant of 2‐4 s. The voltage dependence and kinetics of IB activation were measured. Current amplitude is sensitive to removal of both Na+ and Ca2+ from the bathing medium but the current is not blocked by either tetrodotoxin (TTX) or replacement of Ca2+ by Co+. The amplitude of the current is independent of the external K+ concentration. 4. A slow outward tail current, termed IC, is also activated by depolarization. It is shown to be a K+ current whose activation results from an increase in the cytoplasmic Ca2+ concentration during depolarization. The decay of IC on repolarization requires more than 30 s to reach completion. 5. The slow rates of relaxation of IB and IC tail currents suggest that they are important determinants of the slow membrane potential variations characteristic of burst firing. IB activates more rapidly than IC during depolarization and is thought to be important for maintaining the depolarized phase of the burst cycle and for producing the depolarizing after‐potential after each spike. IC activates more slowly but reaches greater amplitudes. It is thought to be important for adaptation in spike frequency during the burst, for burst termination, and for determining the duration of the interval between bursts.
The receptive‐field spatial structure of cat retinal Y cells.
Authors: Enroth-Cugell C , Freeman A W
Published: December 2014

1. Y‐type ganglion cells in the cat's retina were stimulated with bars of light and grating patterns at photopic luminances. Stimuli were stationary, and luminance at each point was varied sinusoidally in time at 2 Hz. Impulse rates were recorded from single cells. 2. When the stimulus was a narrow bar of light, the impulse rate approached a sinusoidal function of time as contrast was reduced. The linear behaviour of each cell was therefore characterized by taking the limit of response parameters as contrast approached zero. 3. The ratio of surround strength to centre strength varied widely between cells but the two strengths were approximately equal on average. The difference between surround phase and centre phase averaged 168 deg. 4. As contrast increased, responses became rectified. Rectifier output was well described by a power law of stimulus amplitude, where the power was usually 1.4 or 1.5. 5. Response phase advanced with increasing contrast, and at high response amplitudes grew less than proportionally with contrast. These effects were assumed due to the contrast gain control described by Shapley & Victor (1978). 6. Gratings in which luminance varied sinusoidally with distance were used to determine Y cell spatial resolution. The second‐harmonic amplitude of the response diminished rapidly with increasing spatial frequency: the radius of the best‐fitting Gaussian mechanism was about 0.25 deg for a cell at 10 deg eccentricity. 7. This spatial resolution is close to the linear resolution of X cells as determined by Linsenmeier, Frishman, Jakiela & Enroth‐Cugell (1982). 8. A receptive field model incorporating both linear and non‐linear elements is described. The model consists of an array of subunit pathways, each of which has a centre‐surround organization followed by a rectifier; a pool weights and sums subunit outputs, and signals are then passed through a contrast gain control. 9. The model accounts qualitatively for the over‐all centre‐surround organization of Y cell linear responses, the dependence of frequency‐doubled responses on spatial frequency, and impulse rate as a function of time for a variety of bar and grating stimuli.
Two types of synaptic selectivity and their interrelation during sprouting in the guinea‐pig superior cervical ganglion.
Authors: Liestøl K , Maehlen J , Njå A
Published: December 2014

1. The synaptic connexions of the guinea‐pig superior cervical ganglion were examined after collateral sprouting provoked by cutting the preganglionic nerve supply from spinal segments T3‐T7. The selective properties of the connexions made by the remaining segments C8, T1 and T2 were explored both with respect to the segmental origin of the preganglionic axons (Njå & Purves, 1977 a) and with respect to their conduction velocity (Wigston, 1983). 2. After sprouting, the ventral root T1 elicited strong sympathetic effects on both the eye and the ear, while the normal response is largely confined to the region of the eye. This effect on the expressed selectivity was confirmed by intracellular recording in vitro, which showed that virtually all the ganglion cells were now innervated by T1. 3. However, neurones that received dominant innervation from T1 were more frequently innervated by sprouted axons from C8 than were neurones whose dominant innervation derived from T2. This indicates that basic mechanisms promoting segmental selectivity were still functioning. 4. The selective innervation of ganglion cells with respect to the conduction velocity of the preganglionic axons was well maintained after sprouting. 5. These results show that during sprouting from a restricted set of preganglionic axons the synaptic partners are still matched according to both types of selectivity. This suggests that the recognition mechanisms which guide neural development are preserved in adult life, but that the differences in the available sets of preganglionic axons lead to different competitive interactions and different resulting patterns of innervation.
On the role, inactivation and origin of endogenous adenosine at the frog neuromuscular junction.
Authors: Ribeiro J A , Sebastião A M
Published: December 2014

1. The effects of adenosine deaminase, inosine, alkylxanthines (8‐phenyltheophylline (8‐PT), theophylline and isobutylmethylxanthine (IBMX], dipyridamole, alpha, beta‐methylene ADP (AOPCP) and ATP analogues (alpha, beta‐methylene ATP and beta, gamma‐methylene ATP) on evoked end‐plate potentials (e.p.p.s) were investigated in innervated sartorius muscles of the frog, in which twitches had been prevented with tubocurarine. The effects of 8‐PT and IBMX on the amplitude and quantal content of e.p.p.s were also investigated in innervated sartorius muscles of the frog, in which twitches had been prevented with high‐magnesium solutions. 2. Adenosine deaminase reversibly increased the amplitude of e.p.p.s and prevented the reduction caused by exogenously applied adenosine on e.p.p. amplitude. The increase caused by adenosine deaminase was equivalent to the decrease caused by 12 +/‐ 5.8 microM‐adenosine on e.p.p. amplitude. 3. Inosine, the product of adenosine deamination, was virtually devoid of effect on e.p.p.s. 4. The adenosine receptor antagonists at the frog neuromuscular junction, 8‐PT and theophylline, increased in a concentration‐dependent manner the amplitude of e.p.p.s in the presence of tubocurarine. 8‐PT increased the amplitude and quantal content of e.p.p.s in the presence of high magnesium. IBMX, which does not behave as an adenosine receptor antagonist at the frog neuromuscular junction, decreased the amplitude of e.p.p.s in the presence of tubocurarine or high‐magnesium solutions. 5. Dipyridamole, an adenosine uptake blocker, decreased the amplitude of e.p.p.s, and in a concentration that did not affect neuromuscular transmission potentiated the depressing effect of adenosine, but not that of 2‐chloroadenosine, on the amplitude of e.p.p.s. 6. AOPCP, an inhibitor of 5'‐nucleotidase, increased the amplitude of e.p.p.s and markedly attenuated the depressing effect of ATP, but not that of adenosine, on e.p.p. amplitude. 7. The ATP analogue, alpha, beta‐methylene ATP, which is not a substrate for 5'‐nucleotidase, was virtually devoid of effect on e.p.p.s. beta, gamma‐Methylene ATP, which can be a substrate for 5'‐nucleotidase, mimicked the depressing effect of ATP on e.p.p. amplitude, an effect which was also reduced by AOPCP. 8. It is concluded that in conditions in which the initial quantal content is assumed to be normal (1) endogenous adenosine depresses neuromuscular transmission, (2) at the neuromuscular junction adenosine is inactivated through a dipyridamole‐sensitive uptake process, and (3) released adenine nucleotides might contribute to the pool of endogenous adenosine which modulates neuromuscular transmission.
The transfer of visual information across the corpus callosum: spatial and temporal properties in the cat.
Authors: Berardi N , Bisti S , Maffei L
Published: December 2014

1. The spatial and temporal characteristics of the visual information transmitted across the corpus callosum have been studied in normal cats by recording directly from the corpus callosum and in split‐chiasm cats by means of visual evoked potentials (v.e.p.s) and single‐unit recordings at the 17/18 border. 2. The modulation transfer functions (m.t.f.s) obtained by recording from the corpus callosum are comparable to the m.t.f.s evaluated by various techniques for the whole visual system of the cat. The spatial and temporal acuities, however, do not reach the values obtained behaviourally or estimated with cortical evoked potentials. 3. In split‐chiasm cats, both v.e.p.s and single‐unit recordings indicate that the contrast gain of the callosal pathway is considerably lower than the gain of the direct, geniculo‐cortical system. Spatial and temporal acuities are lower for the callosal than for the direct system. 4. The same differences in contrast gain between the spatial m.t.f. obtained for the callosal and the direct system have been found in alert split‐chiasm cats. 5. Our data suggest that the cross‐talk between the hemispheres taking place across the corpus callosum is nearly abolished at low contrasts and high spatial and temporal frequencies.
Parasympathetic nervous control of tracheal vascular resistance in the dog.
Authors: Laitinen L A , Laitinen M V , Widdicombe J G
Published: December 2014

1. The dog trachea has a copious subepithelial vasculature supplied at the cranial end by arteries from the superior thyroid artery. The parasympathetic innervation is partly in the superior laryngeal nerves, stimulation of which causes vasodilatation on both sides. 2. Section of these nerves causes a small dilatation, suggesting that there is no significant resting parasympathetic dilator tone. 3. The dilator response to nerve stimulation is about halved when atropine is given, indicating a cholinergic mechanism. 4. The residual vasodilatation on nerve stimulation in the presence of atropine is reduced but not abolished by hexamethonium, suggesting that an antidromic vasodilator pathway can be activated. 5. Stimulation of the nerves increased tracheal mucosal thickness at the same time as vascular resistance decreased. Thus vasodilator mechanisms of parasympathetic origin may contribute to tracheal mucosal swelling and hyperaemia. 6. There is considerable vascular anastomosis between the two sides of the trachea, and possibly also a crossing‐over of the parasympathetic innervation.