Showing papers in "Journal de physiologie in 1978"

Visual tracking and neuron activity in the post-arcuate area in monkeys.

Abstract: 1. A visual tracking task from a predetermined zone to another predetermined zone with use of a hand was trained in 3 macaque monkeys. They rotated the handle at the wrist joint by flexing or extending. A total of 88 neurons in the posterior bank of the arcuate sulcus, contralateral to the hand used, was related to the task. These neurons were designated as (post-arcuate-) FB neurons, following von Bonin and Bailey's terminology. 2. The FB neurons were classified into 4 types according to their discharge patterns during the task; (1) non-reciprocally, visually coupled neurons (6 neurons); (2) non-reciprocally movement-coupled neurons (41 neurons); (3) reciprocally movement-coupled neurons (17 flexion type and 8 extension type); and (4) finally, non reciprocally movement-coupled depression type neurons (15 neurons). These activations started before the movement onset, as detected in the displacement trace, and were not correlated to the EOG. 3. A possible functional significance of these neurons was discussed. A suggestion was made that in the FB area, after receiving the visual cue information, a function for the later movement direction and tis initiation are produced and sent to the motor apparatus within the brain so that effective tracking task can be performed.

Physiological roles of adenosine derivatives which are released during neurotransmission in mammalian brain.

Abstract: 1. Experiments using synaptosome beds suggested that ATP was released from presynaptic sites and degraded to adenosine in the synaptic cleft and that the resulting adenosine was taken up again into nerve endings where it was re-phosphorylated to ATP. 2. Adenosine derivatives in the synaptic cleft inhibited the postsynaptic potentials in olfactory cortex slices in vitro, presumably by the inhibition of Ca2+ influx into nerve endings which resulted in the reduction of transmitter release. 3. The adenosine derivatives also increased the level of cyclic AMP in the slices under the same conditions as above. 4. Although the nature of the "adenosine receptors" for both functions was remarkably similar, the increase of cyclic AMP did not mediate the inhibitory action, but the presynaptic increase of cyclic AMP induced by adenosine derivatives might mediate the facilitation observed in the olfactory cortex. 5. Possible physiological roles of extracellular adenosine derivatives in mammalian brain were classified, at different sites of action around the synapses, with different time courses and modes of action, directly or via the increase of intracellular cyclic AMP.

Discharge of red nucleus neurons during voluntary muscle contraction: Activity patterns and correlations with isometric force

Abstract: Discharges of red nucleus neurons were analyzed in the cat during voluntary muscle contractions performed under isometric and anisometric conditions. The observations established: (1) that neurons of the red nucleus modulate their firing in advance of the motor output under both conditions; (2) that increased activity of these neurons is specific to the direction of the force exerted ; (3) that this increase is primarily related to the magnitude of the rate of force change generated by the animal.

Activity of pre-entral neurones in conscious monkeys: effects of deafferentation and cerebellar ablation.

Abstract: After limb deafferentation, there was no gross alteration in the initiation and performance of a sound-triggered ballistic movement. The pattern of neuronal discharge in the arm area of the motor cortex was not significantly modified. In the absence of cerebellum, the reaction time of motor cortex cells was about 150 msec longer than the reaction time observed in normal and deafferented animals. This was associated with an equal retardation in the onset of ENG changes in the limb muscles. This observation is compatible with the idea that the motor cortex is normally situated downstream to the cerebellum in the initiation of some movements. However, the motor cortex is necessary for the initiation and execution of simple sound-triggered movements since its removal results in a permanent inability to perform the task. Finally, in the absence of peripheral feedback, the pattern of motor output to the agonistic and antagonistic muscles was initiated normally and thus appeared to be preprogrammed centrally. The importance of the motor cortex as a "reflex center" in the control of slower movements is obviously not challenged by these observations since the motor task that we have used depends very little or not at all on sensory feedback (Stark, 1968). What these results indicate, however, is that the execution of some voluntary fast ballistic movements can be entirely preprogrammed independently of peripheral and cerebellar influences, and that the program, which is mainly concerned with generating velocity signals, appears to require the integrity of the motor cortex for its execution.

Muscle responses and monosynaptic reflexes in falling monkey. Role of the vestibular system.

Abstract: The free fall has been used in our laboratory as a way to test vestibular function in baboons in order to quantify vestibular compensation in the hemilabyrinthectomized animal. This study presents only those results that concern the contribution of the vestibular system to muscle responses due to sudden fall. EMG activity was recorded from the fully conscious animal using chronic electrodes implanted in various muscles. Spinal monosynaptic reflexes (Hoffmann's and tendon reflexes) were studied in the soleus muscle. Baboons were seated in a special chair suspended from an electromagnet and unexpectedly dropped 90 cm. Experiments were performed in normal, unilateral and bilateral vestibular neurectomized baboons. 1. In normal baboons, results showed a first short-latency response in all tested muscles, followed by a second peak of EMG activity in these muscles. Comparison with data from bilateral vestibular neurectomized baboons demonstrates that normal vestibular function is essential for the appearance of the first peak; the second peak rapidly disappears in our experimental situation where the animal's fall is mechanically braked and interrupted, so the animal does not have to make the postural adjustments necessary for landing, It is suggested that the first peak is concerned with the automatic and reflex control of landing, the second with the voluntary breaking of landing. 2. The modulation of monosynaptic spinal reflexes is closely related to the EMG response in soleus muscle. Facilitation of the H-reflex begins just prior to the onset of the EMG activity and continues as long as the baboon is falling. The T-reflex modulation presents a similar time course except in its early phase where it is depressed. Decrease in T and increase in H-reflexes suggest that the EMG response is most likely due to direct activation of alpha-motoneurons and not by means of the gamma-loop. 3. In unilateral vestibular neurectomized baboons, EMG and reflexological data show the classical asymmetry characterized by a strong decrease of the responses on the side of the lesion, and by a pronounced increase on the contralateral side. It is concluded that this represents the imbalance between the resting discharge of the vestibular neurons, and discloses the influence of labyrinthine afferences at the spinal level. We suggest consequently the use of EMG responses and modulation of spinal reflexes to fall in order to quantify vestibular compensation.

Slow inward and outward currents of rat ventricular fibers under anoxia.

Abstract: Voltage and current clamp experiments were performed on rat ventricular strips under anoxia. 1. Under the influence of anoxia the membrane depolarized by 5 to 10 mV and the action potential amplitude decreased by 15 mV. The plateau disappeared and the duration of the action potential was shortened. 2. The slow inward current was reduced by 50 to 80% and its reversal potential became more negative by about 31 mV. The conductance of the slow inward channel decreased by 26%. 3. The net outward current was slightly depressed.

An intracortical microstimulation study of output organization in precentral cortex of awake primates.

Abstract: We investigated the output organization of the forelimb control area in primate precentral cortex by using low-current (less than 30 microamperemeter) intracortical microstimulation (ICMS). Movement about a joint was selected as the index of response. Penetrations perpendicular to the cortical surface and deep into the rostral bank of the central sulcus were made in two awake unanesthetized monkeys (Macaca arctoides). Cortical areas were designated by the joint about which movements occurred. 1. ICMS loci which produced movements about finger joints were found to tightly cluster in a central zone, and were surrounded by loci controlling movement about the wrist. This wrist zone was in turn approximately encircled by an elbow zone, which itself was enclosed by a shoulder zone. 2. Appreciable overlap between these zones controlling movements about contiguous joints was observed. 3. The observations indicate a nested-ring organization of the forelimb output zones of precentral cortex, such that a cortical zone controlling movement of a more distal joint is partly encircled by the zone controlling a more proximal joint.

Red nucleus cell activity in awake cats during a placing reaction.

Abstract: It is known that the discharges of the posterior red nucleus (RN) cells are modulated during locomation (Orlovsky, 1972). The aims of the present investigation were to look for a possible relationship between the unitary activity of RN cells and movements as well as postural reactions of the forelimbs. In the experimental arrangement used, the cat stood on four transducers which recorded to forces on each limb. The animal was restrained by a hammock supporting a part of the total body weight. A horizontally moving plate touched one forepaw and pushed it backwards until a placing mavement was induced. During the first part of the sequence, the mechanically stimulated limb was actively unloaded just prior to the placing movement, while the contralateral forelimb simultaneously presented a loading postural reaction. The results can be summarized and interpreted in the following way: 1. The RN cells exhibit large variations of discharge frequencies during phasic muscular activities linked to movement and to postural adjustments, but no correlations can be established between tonic cell activity and static postural forces exerted by the limb. 2. During the swing phase, the neuronal activity of some RN cells is maximal during flexion, while for others the maximum is during extension. 3. When there is a modification in frequency at the onset of the placing reaction relative to activity during the unloading reaction, the beginning of this change occurs after the onset of the movement as recorded by a potentiometer placed at the elbow joint. 4. The increases of frequency are higher during reciprocal muscle activation (during the movement) than during coactivation of antagonistic muscles (during the postural loading reaction). 5. During the loading reaction (with mostly extensor activation) the frequency of firing of those neurones discharging during the flexion phase. Thus the data may indicate that the RN is included in a feed-back loop which is linked not to muscle activities but rather to phasic spinal reflexes.

Does the supplementary motor area play a part in modifying motor cortex reflexes

Abstract: Neuronal activity in the supplementary motor area was recorded from a monkey performing a trained motor task that required readiness for proper usage of sensory inputs. Thirty-two neurons exhibited activity changes, which supports the hypothesis that the SMA is part of the system involved in modulating responsiveness of the motor cortex to sensory inputs in association with learned movements.

Developing role of sensorimotor cortex and pyramidal tract neurons in contact placing in kittens.

Abstract: Unilateral or bilateral removal of kitten sensorimotor (SM) cortex prior to the fourth postnatal week was followed by recovery of contact placing (CP) to stimulation of any of the four forepaw cutaneous fields. However, immediately after a removal under ethyl chloride, CP was depressed contralaterally, especially to lateral stimulation (lateral CP). When the operated kitten aged to 5--9 weeks, the likelihood of CP secondarily declined contralateral to the SM cortical extirpation, but was restored by administration of d-amphetamine. An initial extirpation after the fifth postnatal week was followed by a severe deficit in CP. 2. Cooling the SM cortex, internal capsule or bulbar pyramid during the 2nd and 3rd week was followed by reversible, contralateral loss of lateral CP, extension of the forelimb and, later, by reduced movements. Lateral CPs were often hypermetric prior to loss. By contrast, cooling SM cortex in the first week was usually ineffective. Thus, during the 2nd week, lateral CP developed a dependence on SM cortex, and in particular on PT neurons. 3. After a delay usually of 1 or more min, cooling the SM cortex reduced the resting discharge of individual neurons in buried motor cortex; the antidromic conduction time in PT neurons was significantly increased and the spike height was reduced.

Effects of denervation on the reduction of sarcomere number in cat soleus muscle immobilized in shortened position during seven days.

Abstract: 1) Immobilization of cat soleus muscle in shortened position for only seven days was sufficient to elicit a marked reduction in the sarcomere number of individual muscle fibres and a considerable decrease in extensibility. 2) These effects were similar to those observed in previous experiments (TABARY et al., 1972) during which the muscles were immobilized for four weeks. 3) When a denervation was made just prior to immobilization, then one noted a marked difference in the change: the sarcomere number was only slightly reduced and there was a very small change of extensibility. The contralateral non denervated side showed the expected reduction of sarcomere number and decrease of extensibility. 4) These results contrast with previous observations made on denervated muscles immobilized for a period of four weeks. 5) It is proposed that the differences in sarcomere number adaptation observed in denervated and non denervated immobilized soleus are caused by differences of sarcomere length between the two muscles caused by the absence of presence of muscle contraction.

The release of ATP triggered by transmitter action and its possible physiological significance: retrograde transmission.

Abstract: 1. When a slice of electric organ of Torpedo is stimulated and superfused with a solution containing a firefly lantern extract, it is possible to measure the release of ATP after each nerve impulse as a light emission. 2. The postsynaptic action of released ACh induces the release of ATP by the postsynaptic cell. Most of the released ATP is of postsynaptic origin. 3. Ion fluxes associated with depolarization, or depolarization itself, trigger the release of ATP from postsynaptic and presynaptic membranes (synaptosomes). 4. ATP is able to block ACh release; a postsynaptic "retrograde transmission" able to control presynaptic transmitter release is possible.

Mechanisms of depression of neuromuscular transmission by ATP and adenosine.

Abstract: 1. The effects of ATP in the presence of theophylline and imidazole were investigated on the twitch tension of a partially magnesium blocked rat phrenic nerve-diaphragm preparation. Both theophylline and imidazole facilitate the neuromuscular transmission and prevent the effects of ATP. 2. The effects of adenosine in solutions with low calcium concentrations in the frog-sartorius and in solutions with very low calcium concentrations in the rat-diaphragm were studied on the miniature end-plate potentials. Adenosine caused a similar reduction of the frequency of the miniature end-plate potentials in both low and very low calcium concentrations. 3. The results are discussed in relation to the cyclic AMP and calcium hypothesis.

Is the rhythm amplitude related to the ability to phase-shift circadian rhythms of shift-workers?

Abstract: The magnitude of the circadian acrophase adjustment deltaphi to a phase shift of socio-ecologic synchronizers (as in shift-work) varies from subject to subject. According to J. Aschoff, the ability to adjust rapidly to a phase-shift could be associated with having a small amplitude for certain circadian rhythms. To test this hypothesis, the correlation coefficient (r) between the mean circadian rhythm amplitude A and the acrophase shift deltaphi (measured after the first night-shift) were calculated from estimates of chronobiological time series analyses (Halberg's single cosinor method). Data were obtained from two groups of selected shift-workers (20 and 5 subjects, respectively). A negative correlation between A and deltaphi (the smaller the amplitude, the greater the delpaphi) was observed in the circadian rhythms of the following variables: oral temperature (r = .63;P less than .01), peak expiratory flow (r = . 53: P less than . 01), and urinary 17-OHCS (r = . 60; P less than . 01), but not for other variables such as : grip strength, urinary K+ and Na+. The small amplitude of certain circadian rhythms could be considered as an index of an individual's ability to phase-shift easily. However, chronobiological characteristics, other than the small circadian rhythm ampliture, remain to be identified, for both a better detection of one's ability to do shift-work and a better knowledge for practical applications.

Properties of the pyramidal tract neuron system within the precentral wrist and hand area of primate motor cortex.

Abstract: 1. To obtain basic anatomical data that will be useful in interpreting the results of studies of primate pyramidal tract neurons (PTNs), extracellular, single-unit recording techniques were used to determine a number of the properties of the PTN population within the electrically defined, precentral wrist zone of the monkey's motor cortex. 2. Recordings were obtained from a total of 1,375 antidromically identified PT and corticospinal tract (CST) cells. A mathematical model was then used to correct the statistics of the sample for variations in the probability of unit detection, which arise from variations in neuronal size and extracellular field dimensions. 3. Both the experimentally observed and theoretically corrected results suggest that the PT projection from this cortical zone is derived principally from slowly conducting, and presumably small to medium-sized cells (an estimated 85% of the resident PTN population). 4. Both the fast and slow cell subpopulations were found to be concentrated within cortical layer V, where they tend to congregate in small, mixed clusters of 2 to 5 neurons. Estimates of the total packing density of PTNs within layer V of this cortical zone suggest that they account for only 10-20% of the neurons within this major efferent layer. 5. 70% of the slow and 82% of the fast PT neurons within this cortical area were found to send their axons into the contralateral, lateral corticospinal tract. Thus, in futur functional studies of PTNs in this cortical area, it can be assumed that three of every four neurons will in fact influence segmental cells of one category or another directly. 6. Extensive data are also presented on the incidence of axon collateral branching from PT and CST cells to the red nucleus, the medial medullary reticular formation and the cuneate nucleus. 7. Some general implications of these findings for the design of future functional studies of anatomically identified motor cortex cell systems are then discussed.

Adenine nucleotides in cholinergic transmission: presynaptic aspects.

Abstract: 1. Isolated nerve terminals (T-sacs and synaptosomes) prepared from the purely cholinergic Torpedo electric organ have been studied for their ability to incorporate and metabolise [2-3H] adenosine and to degrade 5'-AMP to adenosine. 2. A temperature-dependent, saturable uptake system for adenosine was found with kinetic properties similar to nucleoside transport systems in other cells. The uptake system in Torpedo nerve terminals was inhibited by 2'-deoxyadenosine, a known inhibitor of adenosine transport. 3. Intraterminal adenosine is rapidly metabolised to a number of products including AMP, ADP and ATP. 4. Isolated nerve terminals contain considerable 5'-nucleotidase activity, most of which resides on the outer face of the external membrane. The Km of the enzyme is congruent to 5 micron and it is inhibited by a phosphonate analogue of ADP, alpha-beta-methylene-ADP. It is suggested that this 5'-nucleotidase plays an important role in the production of adenosine from a nucleotide pool in the synaptic cleft.

Propriospinal neurones as a relay system for transmission of cortico-spinal influences.

Abstract: 1. Synaptic organization and transmission have been studied in the lateral group of short propriospinal neurones of the lumbar and cervical regions of the cat spinal cord. Special attention was paid to their role in the transmission of cortico-spinal volleys. 2. The majority of these neurones are mono- or oligosynaptically excited after pyramidal tract stimulation. Convergence of excitatory actions from rubrospinal and lateral reticulospinal tracts was typical for these cells. Neurones with relatively low-level and delayed effects from segmental afferents are frequent in this population. 3. Temporal summation is important for the transmission of descending vlleys through these neurones. Mutual excitatory and recurrent inhibitory connections are supposed to play a substantial role in their function. 4. Possible participation of the short lateral propriospinal system in the transmission, transformation and re-distribution of corticofugal signals to the segmental spinal mechanisms is discussed.

Effects of cold adaptation and re-adaptation upon the mitochondrial phospholipids of brown adipose tissue.

Abstract: 1. A study of the mitochondrial phospholipids, phospholipid fatty acid patterns and enzyme activities was investigated in brown tissue (B.A.T.) from rats chronically exposed to cold and/or treated with thyroxine. 2. The total activities of the oxidative enzymes were increased after cold exposure, but not after thyroxine treatment. 3. Cold exposure increased the amount of phosphatidylethanolamine, phosphatidylcholine, cardiolipin and lysophospholipids, the effect being greatest for phosphatidylethanolamine. At the same time, there were marked alterations in the fatty acid composition of the mitochondrial phospholipids (decrease of palmitic, palmitoleic and oleic acids ; increase of stearic, linoleic and arachidonic acids). 4. All these cold-induced alterations were reversed by re-adaptation of the animal to a normal temperature range. 5. The alterations of the fatty acid composition of phospholipids could be explained by changes in the rate of individual fatty acid biosynthesis.

Effects of progesterone and 17-beta-oestradiol treatments on the pancreatic B cell castrated female rats. Biochemical variations.

Abstract: The biochemical effects of progesterone and/or oestradiol treatments on castrated female rats have been compared to those of control olive-oil injections. 1. The steroid treatments used produced physiological concentrations of the two hormones in peripheral plasma, comparable to those obtained during pregnancy. 2. Glycemia remains within a normal range for all the treatments. 3. Circulating immunoreactive insulin (IRI) increases in the steroid-treated rats and the values reach those of the pregnant animals. 4. It was concluded that the biochemical modifications that occur during the steroid treatment (especially with the combined treatment) are quite comparable to what happens during pregnancy and explain, at least in part, the altered carbohydrate and lipid metabolism, and the hyperactivity in the B cell, resulting in an increased insulin secretion.

[Electrotonic transmission in the mammalian central nervous system (author's transl].

Abstract: The aim of this review is to present the electrophysiological data, obtained in the mammalian central nervous system, which show that depolarisations recorded intracellularly, under certain experimental conditions can be interpreted in terms of electrotonic coupling. The results were obtained from very different structures: primary sensory nuclei, sensori-motor integration centres and motor nuclei. The association of the phenomenon of electrotonic transmission with a known ultrastructural substrate--the "gap junction"--has been defined by the term electrotonic coupling. In the cases where it has not been possible to link depolarisations with the presence of gap junctions, other possible morphological correlates have been envisaged. The functional significance of electrotonic interactions are discussed on the basis of information obtained from different experimental approaches.

Supplementary motor area of the monkey: activity of neurones during performance of a learned motor task.

Abstract: 1. Recordings were made of the natural dischages of neurones in the supplementary motor area (SMA) of conscious monkeys trained to perform a stereotyped motor task with either hand. 2. Eighty % of the total population of cells showed modulation of their activity during particular movements of either limb. Two thirds of this group had a similar pattern of modulation regardless of whether the contralateral or ipsilateral hand was used. 3. The number of cells whose activity was related to movements of distal joints was approximately equal to that whose discharges occurred with proximal movements. 4. Only 5% of cells tested sent their axons into the pyramidal tract, and only 15% of units investigated showed responses to passive manipulation of the limbs. The effective afferent input usually was of a rather complex kind. 5. The findings suggest that the discharges of a large number of neurones in SMA are changing during particular movements of either arm, and that only a small number of cells receive afferent sensory input. These results contrast with those obtained in the primary motor area and suggest a different role for SMA the control of movement.

The role of cyclic AMP in the modulation of synaptic efficacy.

Abstract: 1 Heterosynaptic facilitation (modification of synaptic transmission by a neuron influencing the terminals of the presynaptic neuron) was studied in the pleural ganglion of Aplysia Among several identified synapses, heterosynaptic facilitation was observed only in one type (EIPSP synapses) when repetitive stimulation was applied to the tentacular nerve or to a particular identified neuron 2 Serotonin was shown to increase the amplitude of the EIPSP at this synapse; this facilitatory effect was prolonged in the presence of theophylline and mimicked by cyclic AMP 3 When transmission was abolished by calcium-free solution, calcium injected in the region of the synapse caused partial recovery of the EIPSP; when calcium injection was preceded by serotonin injection near the same terminal, the EIPSP was much larger than with calcium injection alone 4 It was concluded that the activation of one neuron (the heterosynaptic neuron) caused it to release serotonin, which activated an adenylate cyclase in the pre-synaptic terminals of another neuron Consequent accumulation of cyclic AMP in these terminals is supposed to have increased their voltage-dependent calcium conductance and hence the amount of transmitter released during an action potential

Extracellular nucleotides in exercise: possible effect on brain metabolism.

Abstract: ATP and other nucleotide derivatives have potent extracellular effects. Sensitive and rapid techniques of ATP detection have shown that ATP is (1) released from active skeletal muscle in vasodilator quantities and (2) released from isolated heart cells in response to hypoxia. Release of nucleotides from active brain tissue has also been demonstrated (Pull and McIlwain, 1972). It is calculated that active cerebral tissue releases sufficient ATP to satisfy local vasodilator requirements in the brain. Intracarotid infusions of ATP have the effect of stimulating oxygen uptake in brain tissue and profoundly increasing the cerebral blood flow. It is not understood how the ATP can exert these effects beyond the blood : brain barrier. Since exercising skeletal muscle releases ATP and other nucleotide derivatives into the circulation, it is postulated that the metabolism of the brain can be significantly affected in exercise. These data, together with the studies by Pritchard et al. (1975) on uptake and supply of purine compounds by the liver, prompt the suggestion that there exists a system of "metabolic communication" in the body mediated by circulating purine compounds.

Some problems of projections and actions of cortico- and rubro-spinal fibres.

Abstract: A review of a number of known, partly known and to be established properties of the cortico- and rubro-spinal tract systems in relation to: (1) multiple projections of individual neurones, or functional subgroups of neurones in the motor cortex and in the red nucleus, (2) identification of spinal target cells of these neurones, and (3) the mechanisms of interactions between the two systems.

Relation of slowly conducting pyramidal tract neurons to specific aspects of forearm movement.

Abstract: PT neurons were recorded from monkeys performing a trained motor task that included tonic maintenance of a limb position, slow and controlled and then quick wrist movements. The results suggest that many of slowly conducting PTNs have preferential relations with specific aspects of slow or tonic motor acts.