Showing papers in "Japanese Journal of Physiology in 1973"

Pentylenetetrazol-induced intracellular potential changes of the neuron of the Japanese land snail Euhadra peliomphala.

Abstract: The effect of Pentylenetetrazol (PTZ, Metrazol) upon the identified neurons of Japanese land snail was studied.1) In the pleuro-parieto-visceral ganglion of Japanese land snail, Euhadra peliomphala, three types of cells can be differentiated morphologically and functionally as those; depolarized by acetylcholine (D-cell), hyperpolarized by acetylcholine (H-cell) and indifferent to acetylcholine (I-cell).2) PTZ produces a phasic depolarization followed by a sustained depolarization in the D- and H-cells.3) PTZ has no specific effect upon the I-cell.4) By application of d-tubocurarine, atropine and hexamethonium, the typical phasic activity evoked by PTZ is not affected in either the D- or H-cells, suggesting that the effect of PTZ is not of synaptic origin but of endogeneous origin.5) Neither cholinergic nor noncholinergic inhibitory input to the Dand H-cells are affected even at the peak of PTZ activity.

Pharmacological properties of cat's collicular auditory neurons.

Abstract: Effects of various drugs on the collicular auditory neurons were examined by means of pressure microinjection and microelectrophoresis methods.1. Acetylcholine had stimulating action on 67% of the nuerons tested. Most of them showed a relatively fast onset and a slow recovery.2. Monosodium-L-glutamate excited 85% of the neurons tested. The action was exerted with a relatively fast time course and by smaller doses than those required for acetylcholine.3. L-aspartic acid also had an excitatory action. It was clearly much weaker than L-glutamate.4. Eserine sulphate stimulated 60% of the neurons tested.5.γ-Aminobutyric acid exerted a potent inhibitory action on both spontaneous discharges and tone-induced responses. The recovery required a much longer time than that needed for the onset of the effect.6. Glycine caused a powerful depression comparable to that of GABA. The neurons tested were of a fast time course of action.7. Atropine sulphate, dihydro-β-erythroidine hydrobromide and d-tubocurarine blocked tone-induced excitation. Atropine had the strongest action among these cholinergic antagonists.8. Disinhibitory effect by picrotoxin was observed with 43% of the “on” type neurons examined, that is, “on” responses were changed to sustained responses. The action of picrotoxin was time-limited in duration to 40-80 msec and mainly affected the discharges during the beginning of the stimulation period.9. Strychnine sulphate was found to have no effect upon “on” type neurons.10. 5-Hydroxytryptamine was also found to have no effect.11. Irreversible blocking effect was observed with tetrodotoxin.12. It is suggested that the receptor sites of the collicular auditory neurons are cholinergic in nature for mediating the excitatory process. GABA may be a principal candidate as an inhibitory transmitter which may produces “on” type responses in the inferior colliculus.

Effects of iontophoretic application of 5-hydroxytryptamine, noradrenaline and acetylcholine upon hypothalamic temperature-sensitive neurones in rats

Abstract: 1) Temperature-sensitive neurones in the preoptic region of rats anesthetized with urethan were examined for responsiveness to iontophoretically applied monoamines and acetylcholine. Investigation was performed on 55 temperature-sensitive neurones (40 warm and 15 cold cells) and 18 temperature-insensitive ones.2) 5-hydroxytryptamine had an excitatory effect on 11 out of 22 warm cells and caused a depression of firing rate in 2 out of 8 cold cells.3) Reduction of activity following noradrenaline administration was observed in 6 out of 20 warm cells, while in the cold cells 3 out of 10 had an increased discharge rate.4) Acetylcholine produced either a decrease or an increase in activity of warm cells and cold cells, but depression was predominant.5) About one-third of temperature-sensitive neurones did not respond to any drugs.6) Interspike interval histograms of spike trains recorded during the thermally steady state of brain showed gamma distribution in most of the responsive cells responding to monoamines and acetylcholine.

Maximum cardiac output related to sex and age.

Abstract: Maximum cardiac output (Qmax) was determined for 233 males (aged 9 through 53 years) and 102 females (aged 9 through 20 years) by the carbon dioxide rebreathing technique during bicycle exercise. Maximum cardiac output of the males progressively increased from 12.5 to 22.0 liter/min until age 17 through 18 years and was maintained at this level until age 24 years. From age 25 years a decrease in Qmax to 16.7 liter/min by age 53 years was observed. Qmax of the females increased from a level of 10.5 liter/min at age 9 years to a Qmaximum of 15.5 liter/min at age 18 years, maintaining this level through age 20 years. Male Qmax for comparable ages above 18 years was 30 % higher than female Qmax . Using the average Qmax value of males of 23-24 years as an optimum value, the decrement in Qmax with each year was approximately 0.9 %.

Effect of caffeine on the neuromuscular junction of the frog, and its relation to external calcium concentration.

Abstract: The effect of caffeine on the neuromuscular transmission was investigated by recording the end-plate potential (e. p. p.) of the frog sartorius muscle using an intracellular microelectrode.2. Caffeine increased the e. p. p. amplitude. The threshold concentration was about 0.5-1×10-4g/ml. The amplitude of e. p. p. was 158±16 of control size in the presence of 3×10-4g/ml caffeine.3. The quantum content was increased in the presence of 2×10-4g/ml and 2.5×10-4g/ml caffeine by factors of about 1.5 and 2, respectively.4. The frequency of the miniature end-plate potential (m. e. p. p.) was in creased by about 3-fold with 3×10-4g/ ml caffeine without an appreciable increase of m. e. p. p. size.5. The potentiating effect of caffeine became more marked when calcium concentration of the external medium was lowered, but the effect was usually transient when the calcium concentration was below 1/10 of the normal value.6. After a train of stimuli at 50 Hz for 30 sec post-tetanic potentiation occurred in the presence of caffeine with the same time course as in the control Ringer's solution.7. It is suggested that caffeine acts on the presynaptic nerve terminal and facilitates the release of calcium from the stored site within the nerve terminal.

Release of glucose from perfused liver preparation in response to stimulation of the splanchnic nerves in the toad

Abstract: 1. The effects of stimulation of the peripheral ends of the splanchnic nerve have been studied in isolated toad liver.2. An increase in glucose concentration in perfusate in response to splanchnic nerve stimulation as well as adrenaline or noradrenaline application was observed.3. Relationship between stimulus frequency and release of glucose was studied. From the experiments it was found that the amount of glucose released from the liver is closely related to the number of electrical pulses applied to the nerve.4. Perfusate accumulated during splanchnic nerve stimulation in an isolated liver preparation showed a vasoconstrictor effect on blood vessels in the rabbit ear. Perfusate accumulated from reserpinized toad liver showed no vasoconstrictor effect.5. Reserpine blocked the effect of nerve stimulation on release of glucose but not that of adrenaline application. Propranolol blocked the effect of stimulation as well as that of adrenaline injection. Dibenamine showed no blocking effect.6. It is concluded that without vagal influence the release of glucose occurs in the liver as the result of splanchnic nerve stimulation via the hepatic innervation in toad.

Effects of caffeine on tension development in dog papillary muscle under voltage clamp.

Abstract: 1. Effects of caffeine on tension in the dog papillary muscle were investigated using a voltage clamp with the double sucrose-gap method.2. An S-shaped relationship between membrane potential and developed tension was obtained in Tyrode solution. An increase of the external calcium concentration produced an upward shift of the relationship and a decrease of calcium, a downward shift.3. Caffeine (10 mM/liter) reduced the peak tension at inside positive potentials in Tyrode solution, but scarcely changed the tension at inside negative potentials.4. An administration of caffeine retarded the relaxation phase at first, but the contraction phase was also gradually slowed.5. The magnitude of tension elicited by an action potential after repetitive voltage clamp pulses was dependent on the magnitude of tension during prior clamp pulses in Tyrode solution, but the dependency disappeared in caffeine-treated preparations.6. It was suggested that a tension development in the dog papillary muscle is largely regulated by the sarcoplasmic reticulum and that caffeine reduces the amounts of Ca taken up by and released from the reticulum.

Depth-electroencephalograms of chickens in wakefulness and sleep

Abstract: Spontaneous EEG activities of the hyperstriatum accessorium, archistriatum, paleostriatum augmentatum and primitivum, dorsal and ventral hippocampus, area entorhinalis, area paraentorhinalis, and optic tectum were recorded simultaneously in unanaesthetized chickens during sleep and wakefulness and subjected to frequency analyses. The results obtained are as follows.1. No regular slow waves such as seen in the hippocampus of mammals during arousal and paradoxical sleep were observed in the hippocampus of chickens.2. No high-voltage fast waves appeared in the archistriatum during arousal.3. Regular alpha-like waves of 8-13 Hz appeared in the paleostriatum primitivum during slow-wave sleep.4. In association with rapid eye movements, monophasic spikes were recorded in the optic tectum of chickens during the paradoxical-sleep phase.5. Frequency analyses revealed that the EEGs of the hyperstriatum accessorium of chickens during arousal and paradoxical sleep contained more developed components of slow waves than in the EEGs of the neocortex of mammals.

The enhancing action of 5'-ribonucleotide on rat gustatory nerve fiber response to monosodium glutamate.

Abstract: Responses of single chorda tympani fibers of rats to gustatory stimulations by monosodium glutamate (MSG) of varying concentrations with or without the presence of a fixed amount of sodium 5'-guanylate (5'-GMP) were recorded. The effect of addition of 5'-GMP to MSG differs according to the response characteristics of the unit. In units predominantly responsive to NaCl, little enhancement was observed in the response magnitude with the addition of 5'-GMP, but in units responding well to sucrose a marked enhancement occurred. In a majority of these units, not only a synergistic enhancement in the response magnitude but also a marked lowering of threshold was obtained after the addition of 5'-GMP. The relative magnitude of enhancement was greater at a lower concentration of MSG, and decreased with increasing concentration. Analysis of the concentration-response magnitude relationships suggests that the synergistic action of MSG and 5'-GMP on gustatory receptors is a mechanism known as ‘competitive and noncompetitive’ sensitization.

Electrical activity of the olfactory bulb in the postnatal rat.

Abstract: The electrical activity of the olfactory bulb (OB) was first clearly observed around 5 days after birth in albino rats it generally consisted of (a) rhythmic “induced” waves, appearing in bursts after inspiration, and (b) “intrinsic” waves of lower amplitude and fast frequency, occurring independently of nasal air flow. The first cortical activity was also observed around the same time, and was very similar to the OB activity, especially to the induced waves. This similarity, however, diminished daily as the rats grew. In adult rats, little correspondence between the two structures was found.A series of experiments suggested the dependence of the cortical activity upon OB induced waves because (1) the latter activity occurred with an almost fixed temporal relation to the former, (2) both cortical and OB activities were simultaneously enhanced in amplitude by (a) strong olfactory stimulation with amyl acetate or xylene as well as (b) higher doses (20 mg/kg) of pentobarbital injected intraperitoneally (i. p.), and (3) the cortical rhythmic activity, appearing in synchrony with the OB induced activity was almost completely abolished (a) when the inspired air was made to by-pass the nasal cavity and (b) after the OB was removed bilaterally.

Release of acetylcholine from perfused cerebral ventricles in unanaesthetized dogs during waking and sleep.

Abstract: The cerebral ventricles were perfused with sterile artificial cerebrospinal fluid in unanaesthetized dogs from a cannula in the lateral ventricle to a cannula either in the upper cervical subarachnoid space or in the aqueduct of Sylvius. The perfusate was assayed for acetylcholine on rat blood pressure or frog rectus muscle. Even when no eserine was added to the perfusion fluid the output of acetylcholine in 475 samples taken during wakeful state was between 0.01 to 5ng/min in 354 (74.5%) and above 5 ng in 53 (11.2%). No acetylcholine was detected in 68 samples (14.3%). In 129 samples obtained during sleep (excluding periods of REM sleep) no acetylcholine was detected in 75 (58%) samples and an output of less than 1 ng/min was observed in the rest. Acetylcholine appeared in the effluent of samples taken during sleep when rapid eye movements occurred or before waking.

Concentration of pancreozymin as a determinant of the exocrine-endocrine partition of pancreatic enzymes

Abstract: 1. Recent evidence suggests that the pancreatic digestive enzymes are secreted not only into the digestive tract via the gland lumen (exocrine), but also into the blood stream (endocrine). This dual secretion has been designated the ‘exocrine-endocrine partition’ of enzymes and their precursors, and was investigated in both the isolated and perfused rat pancreas, and the rat pancreas in situ.2. The release of amylase was accompanied by the release of precursors of proteolytic enzymes either into the common duct or into the portal vein, and it was measured as a representation of release of pancreatic enzymes.3. When the isolated pancreas was perfused with Krebs-Henseleit solution containing pancreozymin 0.2u./ml, the amylase output into the common duct was markedly increased, whereas the output into the vein was slightly increased. When the concentration of pancreozymin was increased up to 1.5u./ml, the output into the vein was markedly increased in contrast to a small increase in the output into duct.4. Corresponding with the increase in output into the vein, acinar cells exhibiting high effective membrane resistances increased in number during perfusion of pancreozymin at a high concentration.5. Enhanced release due to pancreozymin into the vein and into the duct was negated when calcium was omitted from the perfusing medium.6. As a high dose of pancreozymin was injected repeatedly into the rat in situ, the blood concentration of amylase became higher but the increase in the output into the common duct became lower.7. It is concluded that pancreatic enzymes and precursors preserved in zymogen granules may be extruded into the acinar lumen by the common calcium-dependent cellular processes; then, some of the secretory products may leak into the portal vein via enlarged intercellular spaces when a high concentration of pancreozymin is present.

Effects of external Na and Ca on the mouse myometrium in relation to the effects of oxytocin and carbachol.

Abstract: Depolarizing action of 10-3U/ml oxytocin and 10-4g/ml carbachol on pregnant mouse myometrium in ionic solutions containing various concentrations of external Na and Ca was studied.1) Excess Ca (10mM) caused hyperpolarization in normal and in low Na (15.5mM) solutions, and decreased membrane conductance.2) The membrane was depolarized by about 10 mV in low Na solutions (15.5mM) and membrane conductance was decreased. Reduction of external Ca to 0.25 mM caused further depolarization and an increase membrane conductance.3) Depolarization caused by carbachol was reduced in solutions containing low Na or excess Ca. The depolarizing action was restored by reducing external Ca to 0.25mM in low Na solutions. The peak depolarization produced by oxytocin was little affected in any of the above ionic solutions.4) In Na-free solutions, where the membrane was depolarized to -25 mV and contracture was produced, neither oxytocin nor carbachol was effective in producing changes in membrane potential or in tension development.

Effects of reducing the extracellular calcium concentration on the resting potential of frog's skeletal muscle fibers

Abstract: Exposing one end of a frog's toe muscle (ex. dig. long. IV) in a sucrose gap apparatus to a Ca++ -free Ringer solution resulted in a depolarization of about 15 mV in about 20-25 min (or 40-45 min in a choline Ringer solution) with very little further depolarization with continued exposure (1 hr or more). As little as 0.05mm Ca++ was sufficient to prevent or greatly reduce the depolarization. Means and frequency histograms of membrane potentials recorded with intracellular microelectrodes were plotted for fixed time periods of exposure to 0-Ca++ The mean depolarizations were between 12 and 35mV when tested 15 min after exposure to 0-Ca++ but were only about 10-15mV when first tested after a 1-hr exposure; the maximum fall observed was about 55 mV after 90 min and 4 periods of sampling. The most consistent change produced by 0-Ca++ was a flattening and broadening of the frequency histogram. These results suggest that the large falls (>20 mV) in frog' skeletal muscle membrane potentials in 0-Ca++ solutions seen here and often reported by other workers are an artifact produced by the intracellular microelectrodes on the cell membranes made fragile by the reduction in membrane Ca++.

Impulse propagation through the cardiac junctional regions of the axolotl and the turtle.

Abstract: In isolated preparations from the axolotl and turtle hearts thepropagation of impulses through different cardiac tissues was studied. Intracellular records were taken from the various types of fibers. Notchedaction potentials were recorded in two junctional regions: the atrioventricularring (A-V. R.) and the ventricle-bulbus cordis (V-B. C.).The action potential recorded in either the A-V. R. or the V-B. C.regions has a notch in its depolarization phase. The temporal occurrenceof the notch was determined by the activation of the correspondingneighboring tissues. The two components given by the notch can beseparated out by using different experimental variables.The A-V. R. and the V-B. C. junctional regions are constitutedby groups of horizontal fibers. When these are severed from the otheradjacent cardiac tissues, it can be seen that the junctional fibers presentspontaneous activity and that the action potential recorded from themis characterized by a slow rate of rise, absence of a notch, and a slowdiastolic depolarization.In these junctional regions it was found that the conduction velocitywas lower than that of any of the other cardiac tissues (Table 1). Thesejunctional regions are preferential sites for delays and blockages inpropagation.The morphological studies revealed that the cells of the A-V intermediateregion are characterized by:(a) small cross sectional diameter ofcytoplasmic extensions;(b) isolated and scanty myofibrils;(c) abundantglycogen deposits; and (d) sparsity of junctional contacts.The electrophysiological and ultrastructural characteristics reportedhere, point towards the conclusion that in the axolotl and turtle hearts themechanisms that underlie the delays in propagation in the junctional regions are similar to those of the mammalian in spite of the absenceof specialized conductive tissues in the lower species.

The action potential of the myocardial cells of the golden carp.

Abstract: The action potentials of the atrial, ventricular and sinoatrial pacemaker cells of the golden carp were recorded by means of a microelectrode technique. Acetylcholine (10-6g/ml) decreased the slope of the diastolic depolarization of the pacemaker cells. It shortened the action potential duration and caused the hyperpolarization of the atrial fibers. Ventricular fibers are insensitive to acetylcholine. Adrenaline (10-6g/ml) increased the slope of the diastolic depolarization of the pacemaker cells. It increased the amplitude of the plateau phase of both the atrial and ventricular fibers and prolonged their action potential duration. In the atrial fibers the acetylcholine effect was blocked by atropine, while the adrenaline effect was blocked by propranolol, but not by phenoxybenzamine. The pacemaker cells were more resistant to tetrodotoxin than the atrial fibers, while the reverse was true for manganese ions. These results indicate that the action potentials of the myocardial cells of the golden carp are similar to those of mammals or amphibians.

The inhibitory action of caffeine on the smooth muscles of mouse myometrium and guinea pig ileum.

Abstract: The effects of caffeine on mouse myometrium and guineapig ileal muscle were investigated by recording the contractile responseand the membrane activity with an intracellular microelectrode.1) Caffeine in concentrations of 2 to 20mM suppressed the spontaneouscontraction of mouse myometrium. In the ileal muscle, low concentration (2 to 6 mM) caused an initial potentiation of contraction, then a resulting decay. With high concentration (20 mM), the dominanteffect was a relaxation. K contracture of both tissues was suppressedby all caffeine concentrations.2) In mouse myometrium, caffeine caused a hyperpolarization, anincrease in membrane conductance and the suppression of spontaneousspike activity. With high concentration, the response evoked by externalcurrent stimulation became abortive.3) The spike potential in the guinea pig ileal muscle had an amplitudeof about 30 to 50mV and was followed by positive afterpotential. Lowconcentration of caffeine accelerated the normal pattern spike discharge. With high concentration, the membrane was only slightly depolarized, but the frequency of spike discharge increased. The amplitude of spikepotential became larger, and the repolarization slower.4) The different membrane responses to caffeine in mouse myometriumand guinea pig ileal muscle due to their dependence on the interactionbetween the membrane and Ca are discussed.

Effect of water temperature on bradycardia during nonapneic facial immersion in man.

Abstract: Bradycardiac response to nonapneic facial immersion in man was examined at water temperatures of 10, 20, 30, 35, 40, and 47°C. The response was mainly dependent on the water temperature. In general, the colder the water, the greater the response. However, the least response was noted at 40°C; at 47°C the bradycardia was greater than at 40°C. The bradycardiac response was generally more marked in trained swimmers and divers than in subjects unaccustomed to swimming. The magnitude of changes in facial skin temperature appeared to have an additional influence on the cardiac slowing. Heart rate reached the minimum value in 20-30 sec, then tended to return toward the initial rate during immersion. Stimulation of cutaneous cold receptors is assumed to be most responsible for the development of bradycardia on nonapneic facial immersion, and the return of heart rate during immersion may be attributed to adaptation of these receptors.

Spectral analysis of olfactory bulbar responses in rainbow trout.

Abstract: The olfactory bulbar responses induced by chemical stimulation of the nares of rainbow trout were computer analyzed into frequency components. The spontaneous activity of the bulb was predominated by low-frequency components (2-6 Hz). Upon stimulation this immediately shifted to high-frequency components (7-11 Hz). The peak frequency pattern was characteristic of each single chemical tested regardless of the stimulus intensity. Multi-peak spectra were obtained on stimulation with compound stimuli such as food extract. The frequency component coding mechanism for olfactory receptive discriminatory function in the olfactory bulb is discussed.

Desensitization of smooth muscle cells in the guinea pig taenia coli to prolonged application of carbachol.

Abstract: To investigate the mechanism of desensitization to carbachol (Carb) in smooth muscle, the effects of prolonged applications of Carb on the electrical and mechanical properties of the guinea pig taenia coli were examined by either the microelectrode method or the double sucrose gap method.1. Prolonged application of Carb (10-5 g/ml; 5.5×10-5 M) initially depolarized the membrane, reduced the membrane resistance and evoked contracture. These responses did not, however, continue but a desensitization to Carb then developed, i. e. the membrane was gradually repolarized, membrane resistance increased, and the muscle relaxed in spite of the presence of Carb.2. During the repolarization phase in the presence of Carb (10-5 g/ml), repeated current pulses transiently produced larger electrotonic potentials than those expected from the electrical displacement of the membrane potential. This transient increase of the membrane resistance was not directly related to the desensitization and it might be accounted for by a reduction of K permeability in the extrareceptor region at the depolarized condition.3. Desensitization was accelerated in modified Krebs solutions with reduced Na or excess Ca, but was suppressed in solutions either with reduced Ca, or with reduced Cl or with excess K.4. Procaine (27×10-5 g/ml; 1 mM) supPressed both the depolarization and the desensitization induced by Carb. Hypertonic Krebs solution also suppressed the action of Carb on the taenia coli.5. The contrast between the actions of Carb on the taenia coli and frog motor endplate has been discussed in terms of the ionic mechanisms involved.

Evidence for the osmotic flow across dog submaxillary gland epithelia as a cause of salivary secretion

Abstract: In order to clarify the nature of the secretory process of water in dog's submaxillary glands, the following experiments were carried out:(1) measurement of the secretory pressure, (2) measurement of osmolarity of saliva secreted against a high intraluminal pressure, and (3) observation of the effect on the intraluminal pressure of retrograde injection of a hypertonic sucrose solution or an isotonic NaCl solution. It was found that when the secreted saliva was lead to a vertical polyethylene tube the secretion continued until the salivary column reached a height of more than 350 cm with continuous stimulation of the chorda tympani. The osmotic pressure of saliva was examined when it was secreted by stimulation of the chorda tympani into a closed luminal system with a pressure transducer. Under the influence of high luminal pressure (250 mmHg), the osmotic pressure was found to be 350 mOsm, the value being significantly hypertonic as compared with serum. By using the equation ΔP=δRTΔC, which is applicable to the gland system under zero flow conditions, the value of a of the system for salt (probably NaCl) was calculated to be about 0.23. From these findings, it is concluded that the osmosis across some parts of the gland, probably the acinus and the intercalated duct, is very important in water secretion of dog's submaxillary glands, as proposed in the osmotic flow model of Lundberg, Petersen, and Slegers and van't Hof-Grootenboer.

Gustatory coding in the cat chorda tympani fibers sensitive and insensitive to water.

Abstract: 1. Impulse discharges in single chorda tympani fibers of the cat in response to gustatory and thermal stimulations of the tongue were recorded. Fibers were classified into water-sensitive and -insensitive ones; the magnitudes of responses to 0.5 M LiCl, NaCl, CaCl2 and SrCl2 were significantly greater in the latter than in the former.2. The water response in water-sensitive fibers was depressed when a small amount of salts was added to water. The maximum depressing effects were compared among cations of Cl salts and the following order was obtained: Li+>Na+>Sr++>K+>Mg++>Ca++>NH4+. An approximately inverse order was obtained regarding the stimulating action of these cations on water-sensitive fibers.3. Statistical calculations of the frequency of responses of chorda tympani fibers to single gustatory stimuli or combinations of stimuli were made, assuming that responsiveness to any one stimulus is independent of that to other stimuli. No evidence of relatively specific sensitivity to a particular stimulus or a particular combination of stimuli was obtained in the cat.4. Across-fiber correlation coefficients between the degrees of response to a pair of stimuli were calculated. Highly significant correlations were found between HCl and cooling, LiCl and NaCl, CaCl2 and SrCl2, and KCl and either MgCl2 or NH4Cl.

Effects of background illumination on the receptive field organization of single cortical cells in area 18 of the immobilized cat

Abstract: Averaged responses to photic stimuli were recorded from single cortical cells in a circumscribed small region of the nonstriate area (F0-3 and L2-3 in H-C coordinates) of cats. The retinas were stimulated monocularly by various stimuli, such as a diffuse light flash, an intermittent light spot, or a moving light slit, of different sizes and shapes under various conditions of dark and light adaptations. Studies were made on a total of 86 units.1) The cortical cells had relatively large receptive fields, usually about 20°C×20°C. They were responsive to a diffuse flash, and responsiveness was influenced by background illumination.2) The responses of 27 units to a moving slit were suppressed and those of 13 units were facilitated by background illumination.3) Four units showed a reversal of the preferred direction.4) Three units that had no preferred orientation in the dark developed it in the presence of background illumination.5) The response patterns of 39 units were unaltered by background illumination.

The effect of procaine on the urinary bladder smooth muscle of bullfrogs

Abstract: The effect of procaine on the bullfrog urinary bladder smooth muscle was studied with the Rapid Cooling technique, with the following results.1. Procaine induced contracture in the bullfrog urinary bladder smooth muscle in normal Ringer's solution, but it induced a relaxing effect in isotonic potassium Ringer's solution.2. Procaine-induced contracture was inhibited in a low pH Ringer's solution and potentiated in a high solution.3. Mn++ inhibited the procaine-induced contracture, but tetrodotoxin produced no effect.4. The bullfrog urinary bladder smooth muscle contracted in normal and potassium Ringer's solutions when the temperature of the solution was lowered rapidly from 26-28° to 2-4°(Rapid Cooling Contracture, RCC).5. The RCC of the bullfrog urinary bladder in normal and potassium Ringer's solutions was potentiated by procaine, and was inhibited by Mn++.6. The mechanism of the procaine-induced contracture and the effect of Mn++ are discussed with respect to the origin of Ca++. It is postulated that the effect of procaine on bullfrog urinary bladder smooth muscles was produced by mobilization of intracellular bound Ca++, and the inhibitory effect of Mn++ on the procaine-induced contracture and the rapid cooling contracture may be produced by inhibition of its mobilization.

Graphical analysis and experimental determination of the active state in frog skeletal muscle

Abstract: 1) The time course of the active state was calculated bymathematical analysis based on the three-component model and comparedwith the experimental curve determined by quick release or stretchin the small bundle preparation dissected from frog semitendinosusmuscle at 10°C.2) The three-component model contains a contractile component, which consists of a force generator and a viscous-like component, and aseries elastic component. The active state as the force of the force generatoris determined by substituting the tension and velocity curves of thecontractile component for the force-load-velocity relation.3) By this analytical method, the entire active state curve can be determinednot only in the isometric but also in the isotonic contraction.4) The active state of the isometric twitch does not reach its full extentof Po but only 0.7-0.8 Po.5) In the isotonic contraction the duration of the active state decreaseswith decreasing load, and the rate of rise of the active state increasesat the transition from isometric to isotonic contraction.6) The active state curve determined by quick release or quick stretchagrees approximately with the curve determined by the analytical methodwhen the amount of release or stretch is less than 2% of the muscle length, although the experimental curve varies with the amount of release orstretch.