The effect of cerebellectomy on motor activity of the stomach in the ray Dasyatis pastinaca]

It has been shown that after cerebellectomy in rays, motor activity of the stomach undergoes significant changes. From the 1st day after the operation, the frequency of stomach contractions diminishes from 8.30+/-0.46 to 6.30+/-0.50/15 min. Individual variability markedly increases. The amplitude of stomach contractions is also diminished. Sham cerebellectomy does not affect neither the frequency, nor the amplitude of stomach contractions.     

Schistosoma mansoni: effects of bromolysergic acid diethylamide, verapamil, and Ca2+-free solution on the motor activity of the isolated male worm induced by electrical stimulation and oxamniquine

Electrical stimulation and oxamniquine effect the motor activity of isolated Schistosoma mansoni. Electrical stimulation produced contractions that increased with stimulus intensity. Oxamniquine (10(-4) M) produced an increase in basal tonus and in the frequency and amplitude of the worm's spontaneous contractions. Incubation in the absence of calcium produced a decrease in the basal tonus, abolished the spontaneous contractions of S. mansoni, and abolished the mechanical response induced by electrical stimulation and oxamniquine. The effects of electrical stimulation and oxamniquine were, respectively, significantly reduced and abolished by 10(-6) M verapamil (a calcium channel blocking agent). Bromolysergic acid diethylamide (3 X 10(-5) M), a serotonin blocking agent, reduced the motor response induced by high intensity electrical stimulation and blocked the response induced by oxamniquine. The effects of low intensity electrical stimulation were not modified in the presence of bromolysergic acid. We think that external Ca2+ is important for basal tonus, for spontaneous motor activity, and for motor responses of S. mansoni induced by electrical stimulation and oxamniquine. Serotonin may be important for mechanical responses induced by high intensity electrical stimulation and for responses induced by oxamniquine.     

Effects of cold and heat on behavior and cerebellar function in goldfish

Summary A similar sequence of behavioral effects was observed for either cooling or heating; most effects occurred on changing temperature of entire fish or of only the cerebellum. On moderate heating or cooling, fish are hyperexcitable, spontaneously hyperactive; on further heating or cooling swimming is uncoordinated; when the subcerebellar structures are heated or cooled, equilibrium is disturbed; on further heating or cooling coma and respiratory failure ensue. Critical temperatures are modifiable by acclimation. The behavioral effects of cerebellectomy are additive with temperature effects on motor centers.Electrical activity of Purkinje neurons changes in the same thermal ranges as behavior. Inhibition via cerebellar interneurons is most sensitive and can be modified by acclimation. Ongoing activity increases with warming up to a blocking temperature; interspike interval histograms show pattern changes during warming. Activation via mossy fibers-granule cells is more sensitive than that via climbing fibers, and antidromic impulses are most resistant.A neuronal model based on inhibitory actions of Purkinje neurons on motor centers and parallel feedback excitatory pathways can explain both behavioral and electrical observations.     

RNA synthesis in different regions of rat brain at various time intervals after cerebellectomy

RNA synthesis was studied in cerebral cortex, thalamus and brain stem of rat, on the 3rd, 8th, 30th and 75th day after cerebellectomy. An increased RNA synthesis was detected in thalamus at the 30th day and in cerebral cortex and brain stem at the 75th day after cerebellectomy. Our findings suggest that motor compensation following the cerebellectomy could be supported by a spatio-temporal organization of macromolecular synthesis in different brain regions.     

Neural regulation of slow-wave frequency in the murine gastric antrum

Gastric peristaltic contractions are driven by electrical slow waves modulated by neural and humoral inputs. Excitatory neural input comes primarily from cholinergic motor neurons, but ACh causes depolarization and chronotropic effects that might disrupt the normal proximal-to-distal spread of gastric slow waves. We used intracellular electrical recording techniques to study cholinergic responses in stomach tissues from wild-type and W/W(V) mice. Electrical field stimulation (5 Hz) enhanced slow-wave frequency. These effects were abolished by atropine and the muscarinic M(3)-receptor antagonist 4-diphenylacetoxy-N-methylpiperidine methiodide. ACh released from nerves did not depolarize antral muscles. At higher rates of stimulation (10 Hz), chronotropic effects were mediated by ACh and a noncholinergic transmitter and blocked by muscarinic antagonists and neurokinin (NK(1) and NK(2))-receptor antagonists. Neostigmine enhanced slow-wave frequency, suggesting that the frequency of antral pacemakers is kept low by efficient metabolism of ACh. Neostigmine had no effect on slow-wave frequency in muscles of W/W(v) mice, which lack intramuscular interstitial cells of Cajal (ICC-IM). These muscles also showed no significant chronotropic response to 5-Hz electrical field stimulation or the cholinergic agonist carbachol. The data suggest that the chronotropic effects of cholinergic nerve stimulation occur via ICC-IM in the murine stomach. The capacity of gastric muscles to metabolize ACh released from enteric motor neurons contributes to the maintenance of the proximal-to-distal slow-wave frequency gradient in the murine stomach. ICC-IM play a critical role in neural regulation of gastric motility, and ICC-IM become the dominant pacemaker cells during sustained cholinergic drive.     

The effect of pentagastrin and ornithine-tetragastrin on motor activity of the stomach in skates and scorpion-fish]

Low doses of pentagastrin (50 mug/kg b. w.) have no physiological effect on motor activity of the stomach in the skate Dasyatis pastinaca. Average doses (100-200 mug/kg) stimulate the activity, whereas high ones (300 mug/kg) inhibit the frequency of stomach contractions, slightly increasing their amplitude. Ornithine tetragastrin in a dose 2000 mug/kg does not affect motor activity of the stomach in skates. In the scorpion-fish Scorpaena porcus, ornithine tetragastrin (1000 and 2000 mug/kg) inhibits motor activity of the stomach.     

Gastric and duodenal motility in the cat: the role of central innervation assessed by transient vagal blockade

Experiments were performed on four cats to characterize fasting gastric and small bowel motility and to assess the role of extrinsic vagal innervation in the control of that motor activity. A multilumen manometry tube was positioned to record pressure changes from the proximal small bowel and stomach. Transient vagal nerve blockade was accomplished by cooling the cervical vagosympathetic nerve trunks, previously isolated in skin loops on each side of the neck. Two characteristic patterns of basal activity were documented in the stomach: (i) regular phasic contractions of variable amplitude in the body of the stomach; and (ii) infrequent, irregular contractions of high amplitude in the distal antrum. In the duodenum, two predominant activity patterns were noted: (i) periods of continuous irregular activity; and (ii) irregular clusters of contractions separated by quiescent intervals. No typical migrating motor complex activity was seen in the basal gastric or small bowel recordings. Bilateral vagal blockade did not consistently change the general pattern of gastric or small bowel activity, but did appear to reduce gastric contractile activity, as measured by motility indices. We conclude that extrinsic vagal innervation does not play a major role in the control of fasting feline gastric and duodenal motility.     

Cholinergic transmission at mechanosensory afferents in the crayfish terminal abdominal ganglion

Electrical stimulation of mechanosensory afferents innervating hairs on the surface of the exopodite in crayfish Procambarus clarkii (Girard) elicited reciprocal activation of the antagonistic set of uropod motor neurones. The closer motor neurones were excited while the opener motor neurones were inhibited. This reciprocal pattern of activity in the uropod motor neurones was also produced by bath application of acetylcholine (ACh) and the cholinergic agonist, carbamylcholine (carbachol). The closing pattern of activity in the uropod motor neurones produced by sensory stimulation was completely eliminated by bath application of the ACh blocker, d-tubocurarine, though the spontaneous activity of the motor neurones was not affected significantly. Bath application of the acetylcholinesterase inhibitor, neostigmine, increased the amplitude and extended the time course of excitatory postsynaptic potentials (EPSPs) of ascending interneurones elicited by sensory stimulation. These results strongly suggest that synaptic transmission from mechanosensory afferents innervating hairs on the surface of the tailfan is cholinergic.Bath application of the cholinergic antagonists, dtubocurarine (vertebrate nicotinic antagonist) and atropine (muscarinic antagonist) reversibly reduced the amplitude of EPSPs in many identified ascending and spiking local interneurones during sensory stimulation. Bath application of the cholinergic agonists, nicotine (nicotinic agonist) and oxotremorine (muscarinic agonist) also reduced EPSP amplitude. Nicotine caused a rapid depolarization of membrane potential with, in some cases, spikes in the interneurones. In the presence of nicotine, interneurones showed almost no response to the sensory stimulation, probably owing to desensitization of postsynaptic receptors. On the other hand, no remarkable changes in membrane potential of interneurones were observed after oxotremorine application. These results suggest that ACh released from the mechanosensory afferents depolarizes interneurones by acting on receptors similar to vertebrate nicotinic receptors.Abbreviations ACh cetylcholine - mns motor neurones - asc int ascending interneurone     

The motor activity of the chick embryo and amnion during embryogenesis

Studies have been made on the motor activity of amnion and chick embryo from the 5th to the 14th day of development. Between the 5th and the 8th day of embryogenesis, when embryonic movements are rather poor, amnion contractions are mainly observed, their frequency being maximum to the 7th day. On further development (8-14 days), with the increase in the mass of the limbs which account for embryonic movements (body extremities), the increase in the intensity of their motor activity is paralleled by the decrease in the frequency of amnion contractions. Therefore, during the intensive growth and development of mainly frontal part of the embryo, the deficiency of motor activity of rather undeveloped body and extremities is presumably compensated by temporal motor activity of the amnion. Between the 8th and the 10th day, synchronous movements of embryo and amnion are observed. Possible mechanisms of synchronization are discussed.     

Sensory interaction with central ‘generators’ during respiration in the dogfish

Summary The activity in sensory and motor nerves of the gills was recorded from selected branches of the vagus nerve in decerebrate dogfish,Scyliorhinus canicula. Vagal motoneuronal activity was observed at the start of the rapid pharyngeal contraction and was followed by sensory nerve activity which preceded the slow expansion phase. Rhythmical vagal motoneuronal activity was still present after all movements had been prevented by curare paralysis although the frequency of the rhythm was higher than in the ventilating fish. Electrical stimulation of vagal sensory fibres had 3 effects on the ventilatory movements. (1) It evoked a reflex contraction of several gill muscles after a latency of about 11 ms. (2) It could reset the respiratory cycle because a stimulus given during expansion delayed the onset of the subsequent contraction. (3) The stimulus could entrain the rhythm if it was given continuously at a frequency close to that of ventilation. The vagal motor rhythm was disrupted by trigeminal nerve stimulation in the paralyzed fish but not if the motor rhythm was being entrained by vagal nerve stimulation. Vagal sensory activity may be important, therefore, in maintaining the stability of the generating circuits.Abbreviation LED Light emitting diode     

Oxygen availability and motor unit activity in humans.

Six men were studied to determine the interrelationships among blood supply, motor unit (MU) activity and lactate concentrations during intermittent isometric contractions of the hand grip muscles. The subjects performed repeated contractions at 20% of maximal voluntary contraction (MVC) for 2 s followed by 2-s rest for 4 min with either unhindered blood circulation or arterial occlusion given between the 1st and 2nd min. The simultaneously recorded intramuscular MU spikes and surface electromyogram (EMG) data indicated that mean MU spike amplitude, firing frequency and the parameters of surface EMG power spectra (mean power frequency and root mean square amplitude) remained constant during the experiment with unhindered circulation, providing no electrophysiological signs of muscle fatigue. Significant increases in mean MU spike amplitude and frequency were, however, evident during the contractions with arterial occlusion. Similar patterns of significant changes in the surface EMG spectra parameters and venous lactate concentration were also observed, while the integrated force-time curves remained constant. These data would suggest that the metabolic state of the active muscles may have played an important role in the regulation of MU recruitment and rate coding patterns during exercise.     

The enhancement of the reflex reactions of the rat spinal cord after ablation of the cerebellum]

The character of evoked monosynaptic responses of spinal cord 3 weeks after total or partial ablation of cerebellum was studied on white rats. There was a substantial increase of amplitude of this response on the side of hemicerebellectomy and of animals with total cerebellectomy. In acute experiments cutting of spinal cord does not remove hyperreflexia.     

Long-term facilitation and long-term adaptation at synapses of a crayfish phasic motoneuron

Stimulation of the phasic (fast) motor axon of the isolated crayfish claw preparation at relatively low frequency (0.1 Hz) leads to depression of the excitatory junction potential (EJP) recorded from single muscle fibers. When the same stimulation is delivered following depression of the EJP at a higher frequency (5 Hz), a potentiated EJP appears, which is more resistant to low frequency depression. The potentiation appears to be analogous to "long-term facilitation" observed after stimulation of a tonic motor axon in crayfish and crabs. Long-term facilitation can be detected in preparations made from claws of animals in which the phasic motoneuron was stimulated at 5 Hz for 2 h in situ. This effect lasts for at least one day after one conditioning trial. Long-term facilitation is observed after stimulation of decentralized axons in situ, indicating that the change is attributable to local changes in terminal regions of the axon, and does not require the cell body. When electrodes are implanted in situ and the phasic motoneuron stimulated at 5 Hz for 2 h each day, synaptic depression becomes less pronounced and initial EJP amplitude becomes smaller over a period of several days. The latter changes, which adapt the neuron to a more tonic activity pattern, usually require several days for completion. Adaptation of fatigability occurs more rapidly than adaptation of initial EJP amplitude, and once established, remains for many days without further superimposed activity. Long-term adaptation does not occur in decentralized axons. Long-term facilitation and long-term adaptation are different responses of the neuron to enhanced activity. The former can occur in isolated or decentralized axons and leads to enhancement of EJP amplitude for a period of several hours to at least one day after a single episode of conditioning. The latter requires more time to be established, and leads to reduction of initial EJP amplitude and to lessened fatigability which persists for many days.     

Effect of neurogenic inactivity on posttetanic responses of rat fast muscle

At a short-term tetanic stimulation of fast muscle in response to subsequent single stimulation there is recorded a temporary increase of the strength of single contractions that returns to the initial background after 6–10 min. This phenomenon is called posttetanic potentiation (PTP) and is recorded only in fast muscles. The goal of the present work was a study of effect of motor innervation on the course of PTP in rat m. extensor digitorum longus (m. Edl). It has been established that the first signs of effect of motor denervation on the PTP course after section of sciatic nerve in the area of popliteal fossa are recorded as early as at the 4th day after denervation and are expressed in a decrease of strength of single contractions after cessation of tetanic stimulation. These changes reach its maximum at the 14–15th day after denervation when effect of PTP in denervated muscle does not appear at all. Pharmacological analysis of the studied phenomenon has shown that dantrolen (10 μM) suppresses amplitude of the single contraction, but does not prevent the appearance of PTP in intact muscle. In the denervated m. Edl, instead of the appearance of PTP, after a brief slight increase, a gradual decrease of the strength of contraction is recorded. Thus, it can be concluded that no significant PTP changes are present under action of dantrolen. It has been established that after the 10-min muscle incubation in Ringer’s solution with caffeine (4 mM), strength of the single contraction in intact and denervated muscles increases by approximately equal value. Tetanization of intact muscle increases strength of the single contraction approximately by 7% more than this occurs after incubation with caffeine, i.e., this substance reduces the capability of muscle for the appearance of PTP. On denervated muscle, caffeine increases strength of singly contraction, but does not potentiate development of PTP. The obtained data allow concluding about the existence of different mechanisms underlying the pretetatnic contraction and posttetanic potentiation of the single contraction. The main difference between two types of contractions can be recruiting of additional DICR-channels in the process of contraction under conditions of PTP.     

Wide-pulse-width, high-frequency neuromuscular stimulation: implications for functional electrical stimulation.

Electrical stimulation (1-ms pulses, 100 Hz) produces more torque than expected from motor axon activation (extra contractions). This experiment investigates the most effective method of delivering this stimulation for neuromuscular electrical stimulation. Surface stimulation (1-ms pulses; 20 Hz for 2 s, 100 Hz for 2 s, 20 Hz for 3 s) was delivered to triceps surae and wrist flexors (muscle stimulation) and to median and tibial nerves (nerve stimulation) at two intensities. Contractions were evaluated for amplitude, consistency, and stability. Surface electromyograph was collected to assess how H-reflexes and M-waves contribute. In the triceps surae, muscle stimulation produced the largest absolute contractions (23% maximal voluntary contraction), evoked the largest extra contractions as torque increased by 412% after the 100-Hz stimulation, and was more consistent and stable compared with tibial nerve stimulation. Absolute and extra contraction amplitude, consistency, and stability of evoked wrist flexor torques were similar between stimulation types: torques reached 11% maximal voluntary contraction, and extra contractions increased torque by 161%. Extra contractions were 10 times larger in plantar flexors compared with wrist flexors with muscle stimulation but were similar with nerve stimulation. For triceps surae, H reflexes were 3.4 times larger than M waves during nerve stimulation, yet M waves were 15 times larger than H reflexes during muscle stimulation. M waves in the wrist flexors were larger than H reflexes during nerve (8.5 times) and muscle (18.5 times) stimulation. This is an initial step toward utilizing extra contractions for neuromuscular electrical stimulation and the first to demonstrate their presence in the wrist flexors.     

Short-term effect of androgen deprivation on intraluminal pressure and contractility of the rat epididymis

Short-term effects of bilateral castration, cyproterone acetate and unilateral efferent duct ligation on intraluminal pressures and spontaneous contractions in different regions of the epididymis were studied in the rat. Ligation of the efferent ducts for 5 days did not alter pressures or spontaneous contractions in any region of the epididymis. However, bilateral castration produced time-dependent changes in pressures and contractions in different segments. In the caput, the amplitude, but not the basal pressure or the frequency, of spontaneous contractions increased by Day 1 after operation. In the corpus, increments in the basal pressure and the amplitude of contractions occurred by Day 5 whilst the frequency of contractions was not changed. Similar effects were observed in the cauda by 3 days after castration. Changes in all regions of the epididymis were also mimicked by cyproterone acetate treatment (10 mg/rat per day, s.c. for 21 days). In addition, this drug increased the amplitude of contractions in the cauda. The effect of castration was abolished by testosterone propionate (0.2 mg/kg per day, i.m. for 5 days). The results support the suggestion that an enhancement of sperm transport through the rat epididymis occurs shortly after castration. The results also suggest that, in normal rats, androgens suppress the contractility of the epididymal tubule to ensure an optimal rate of sperm transport.     

Glutatmine synthetase activity in the chick brain during postnatal growth. Effect of MSO

Glutamine synthetase activity was estimated in the chick cerebral hemispheres, optic lobes and cerebellum between the 1st and the 30th day of postnatal growth. Glutamine synthetase activity is higher in the cerebellum than in the cerebral hemispheres and lowest in the optic lobes at 1 day after hatching; at 30 days after hatching, it is the same in the optic lobes and in the cerebellum and lowest in the cerebral hemispheres. The great increase of glutamine synthetase activity between the 1st and the 4th day after hatching corresponds to the appearance of the heterogeneity of the chick brain glutamate metabolism. The glutamine synthetase activity is inhibited by MSO $\text{in vivo}$ at a concentration of 100 mg kg ^?1 at values of 87, 90 and 89 % in cerebral hemispheres, optic lobes and cerebellum of 1, 2 and 4-day-old chicks. The enzyme inhibition is less pronounced $\text{in vitro}$ and reaches values of about 25 and 75 % for 1 and 10 mM MSO concentrations respectively in the three brain areas of the 1 to 4-day-old chick and values slightly lower in the 30-day-old chick brain.     

Behavior of trout fry <Emphasis Type="Italic">Salmo gairdneri</Emphasis> during swinging

Ten experimental and 10 control experiments on a parallel swing and 4 experiments on a rotating stand were carried out on fries of the trout Salmo gairdneri, strain Rofor. Depending on changes of motor activity the fish can be separated into three groups: (1) the “freezing” fish, in which the mean swimming rate dropped sharply with the beginning of swinging; (2) the shuttleswimming fish, in which the mean swimming rate in the process of swinging practically did not change, but which with beginning of swinging started the from-wall-to-wall swimming in the horizontal plane by changing direction of the movement with a frequency close to the swinging frequency; (3) the “restless” fish, in which significant fluctuations of the mean swimming rate were observed. A decrease of the motor activity in the first group fish seems to be a protective reaction. By “freezing,” they decrease the vestibular apparatus stimulation. Analysis of the available data allows thinking that the shuttle swimming is based on an unconditional rheoreaction characteristic of pelagic fish. Its realization during swinging depends on activity of otolith organs that until now have not been considered a possible sensor for realization of the rheoreaction. Taking into account the principal role of otoliths in this process, we called this rheoreaction variant the otolithotropic reaction. With increase of stimulus strength, the shuttle movement frequency becomes equal to stimulation frequency. At the same time, sharpness of the otolith reaction is gradually deteriorated, which, however, is not associated with the fatigue of the fish. In fish of the third group, the behavioral changes that are as pronounced as those in fish of the two former groups were not revealed. However, the character of behavior of this fish group with increase of time and amplitude of the variable acceleration is to be elucidated. Thus, we have managed for the first time to describe a new fish reaction to swinging—the otolith reaction and to confirm the conclusion that the swinging affects the fish motor activity [1]. We suggest that a sharp decrease of the mean swimming rate and a disturbance of otolith reaction are the signs of the fish motion sickness.     

The effect of extragastric vagotomy on gastric emptying and motility of the small intestine

Selective parasympathetic denervation of small and some large intestine has been performed in dogs. Chronic experiment on these dogs has revealed that this operation: has no effect on frequency and amplitude of intestine contractions during the first phase of the digestive process but it is accompanied by significant relaxation of the motor intestine activity in the second phase, causes a retardation of the rate of evacuation from stomach by 56.0% in dogs subjected to extragastric vagotomy as well as pH of chyme in the duodenum by 1-1.5 units above the norm.     

Behavior of trout fry Salmo gairdneri during swinging

Ten experimental and 10 control experiments on a parallel swing and 4 experiments on a rotating stand were carried out on the fries of the trout Salmo gairdneri, strain Rofor. Depending on changes of motor activity the fish could be divided into three groups: the "freezing" fish, in which the mean swimming rate dropped sharply with the beginning of swinging; (2) the shuttle-swimming fish, in which the mean swimming rate in the process of swinging practically did not change, but which with beginning of swinging started the from-wall-towall swimming in the horizontal plane by changing direction of the movement with a frequency close to the swinging frequency; (3) the "restless" fish, in which significant fluctuations of the meanswimming rate were observed. A decrease of the motor activity in the first group fish seems to be a protective reaction. By freezing, they decrease the vestibular apparatus stimulation. Analysis of the available data allows thinking that the shuttle swimming is based on an unconditional rheoreaction characteristic of pelagic fish. Its realization during swinging depends on activity of otolith organs that until now have not been considered a possible sensor for realization of the rheoreaction. Taking into account the principal role of otoliths in this process, we called this rheoreaction variant the otolithotropic reaction. With increase of stimulus strength, the shuttle movement frequency becomes equal to the stimulation frequency. At the same time, sharpness of the otolith reaction is gradually deteriorated, which, however, is not associated with fatigue of the fish. In fish of the third group, the behavioral changes that are as pronounced as those in fish of the two former groups were not revealed. However, it is to find out the character of behavior of this fish group with increase of time and amplitude of the variable acceleration. Thus, we have managed for the first time to describe a new fish reaction to swinging--the otolith reaction and to confirm the conclusion that the swinging affects the fish motor activity. We suggest that a sharp decrease of the mean swimming rate and a disturbance of otolith reaction are signs of the fish motion sickness.