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The Journal of Physiology May 2015This study examined motoneurone properties during fictive locomotion in the adult rat for the first time. Fictive locomotion was induced via electrical stimulation of... (Comparative Study)
Comparative Study
This study examined motoneurone properties during fictive locomotion in the adult rat for the first time. Fictive locomotion was induced via electrical stimulation of the mesencephalic locomotor region in decerebrate adult rats under neuromuscular blockade to compare basic and rhythmic motoneurone properties in antidromically identified extensor motoneurones during: (1) quiescence, before and after fictive locomotion; (2) the 'tonic' period immediately preceding locomotor-like activity, whereby the amplitude of peripheral flexor (peroneal) and extensor (tibial) nerves are increased but alternation has not yet occurred; and (3) locomotor-like episodes. Locomotion was identified by alternating flexor-extensor nerve activity, where the motoneurone either produced membrane oscillations consistent with a locomotor drive potential (LDP) or did not display membrane oscillation during alternating nerve activity. Cells producing LDPs were referred to as such, while those that did not were referred to as 'idle' motoneurones. LDP and idle motoneurones during locomotion had hyperpolarized spike threshold (Vth ; LDP: 3.8 mV; idle: 5.8 mV), decreased rheobase and an increased discharge rate (LDP: 64%; idle: 41%) during triangular ramp current injection even though the frequency-current slope was reduced by 70% and 55%, respectively. Modulation began in the tonic period immediately preceding locomotion, with a hyperpolarized Vth and reduced rheobase. Spike frequency adaptation did not occur in spiking LDPs or firing generated from sinusoidal current injection, but occurred during a sustained current pulse during locomotion. Input conductance showed no change. Results suggest motoneurone modulation occurs across the pool and is not restricted to motoneurones engaged in locomotion.
Topics: Action Potentials; Adaptation, Physiological; Animals; Cats; Decerebrate State; Electric Stimulation; Female; Hindlimb; Locomotion; Models, Animal; Motor Neurons; Rats; Rats, Sprague-Dawley
PubMed: 25809835
DOI: 10.1113/JP270239 -
Journal of Neurophysiology Jun 2005The c-fos immunohistochemical method of activity-dependent labeling was used to localize locomotor-activated neurons in the adult cat spinal cord. In decerebrate cats,... (Comparative Study)
Comparative Study
The c-fos immunohistochemical method of activity-dependent labeling was used to localize locomotor-activated neurons in the adult cat spinal cord. In decerebrate cats, treadmill locomotion was evoked by electrical stimulation of the mesencephalic locomotor region (MLR). Spontaneous or MLR-evoked fictive locomotion was produced in decerebrate animals paralyzed with a neuromuscular blocking agent. After bouts of locomotion during a 7- to 9-h time period, the animals were perfused and the L3-S1 spinal cord segments removed for immunohistochemistry. Control animals were subjected to the same surgical procedures but no locomotor task. Labeled cells were concentrated in Rexed's laminae III and IV of the dorsal horn and laminae VII, VIII, and X of the intermediate zone/ventral horn after treadmill locomotion. Cells in laminae VII, VIII, and X were labeled after fictive locomotion, but labeling in the dorsal horn was much reduced. In control animals, c-fos labeling was a small fraction of that observed in the locomotor animals. The results suggest that labeled cells in laminae VII, VIII, and X are premotor interneurons involved in the production of locomotion, whereas the laminae III and IV cells are those activated during locomotion due to afferent feedback from the moving limb. c-fos-labeled cells were most numerous in the L5-L7 segments, consistent with the distribution of locomotor activated neurons detected through the use of MLR-evoked field potentials.
Topics: Animals; Cats; Cell Count; Decerebrate State; Exercise Test; Immunohistochemistry; Locomotion; Motor Neurons; Proto-Oncogene Proteins c-fos; Spinal Cord
PubMed: 15634712
DOI: 10.1152/jn.00578.2004 -
British Journal of Pharmacology and... Feb 1964On the isolated vas deferens of the guinea-pig angiotensin potentiated strongly the height of contractions due to electrical stimulation of the hypogastric nerve; it did...
On the isolated vas deferens of the guinea-pig angiotensin potentiated strongly the height of contractions due to electrical stimulation of the hypogastric nerve; it did not affect the responses to noradrenaline and acetylcholine, nor did it elicit any contraction when given alone. Angiotensin likewise potentiated the responses of the cat spleen to nerve stimulation, but it also induced by itself strong contractions of the organ and reduction of the venous outflow. In experiments on the arterial blood pressure of anaesthetized and spinal cats, in which sympathetic postganglionic transmission was temporarily blocked by nicotine or tetramethylammonium, pressor responses to angiotensin were strongly reduced. As with some ganglion-stimulating drugs, the pressor responses, enhanced after a second series of nicotine injections, were reduced to the control level by hexamethonium. These findings indicate the involvement of peripheral sympathetic nerves in the action of angiotensin: the hypothesis is advanced that angiotensin acts at the peripheral nerve endings by promoting a greater output of noradrenaline.
Topics: Acetylcholine; Angiotensins; Animals; Blood Pressure; Cats; Decerebrate State; Electric Stimulation; Guinea Pigs; Hexamethonium Compounds; Humans; Hypogastric Plexus; Male; Nicotine; Norepinephrine; Pharmacology; Physiology; Quaternary Ammonium Compounds; Research; Spleen; Sympathetic Nervous System; Vas Deferens
PubMed: 14126053
DOI: 10.1111/j.1476-5381.1964.tb01561.x -
The Journal of Physiology Mar 19811. Tonic labyrinth and neck reflexes were studied separately and in combination in the decerebrate cat before and after acute cerebellectomy. Reflex effects were...
1. Tonic labyrinth and neck reflexes were studied separately and in combination in the decerebrate cat before and after acute cerebellectomy. Reflex effects were observed as changes in the length of the medial head of triceps in both forelimbs. 2. In the decerebrate cat with an intact cerebellum the tonic labyrinth reflexes, elicited by side-up and side-down head rotations, produced asymmetric length changes in the medial head of triceps in both forelimbs, as described by Lindsay, Roberts & Rosenberg (1976). After cerebellectomy, head movements in either direction produced reflex shortenings in the medial triceps in both forelimbs, in contrast to the normal reciprocal reflex length changes. The presence of the cerebellum is thus required for the occurrence of the normal asymmetric labyrinth reflexes. 3. The direction of the neck reflexes remained unchanged by cerebellectomy. 4. It is suggested that the postural disturbances following cerebellar damage may partly result from the change in the form of the tonic labyrinth reflexes, which in combination with the tonic neck reflexes would no longer act in a stabilizing manner on the trunk.
Topics: Animals; Cats; Cerebellum; Decerebrate State; Ear, Inner; Forelimb; Head; Muscles; Neck Muscles; Posture; Reflex; Rotation
PubMed: 7264988
DOI: 10.1113/jphysiol.1981.sp013619 -
Journal of Neurophysiology Apr 2009One of the characteristics of respiratory motor output is the presence of fast synchronous oscillations, at rates far exceeding the basic breathing rhythm, within a...
One of the characteristics of respiratory motor output is the presence of fast synchronous oscillations, at rates far exceeding the basic breathing rhythm, within a given functional population. However, the mechanisms responsible for organizing phrenic output into two dominant bands in vivo, medium (MFO)- and high (HFO)-frequency oscillations, have yet to be elucidated. We hypothesize that GABA(A)ergic and glycinergic inhibition within the phrenic motor nucleus underlies the specific organization of these oscillations. To test this, the phrenic nuclei (C(4)) of 14 unanesthetized, decerebrate adult male Sprague-Dawley rats were microinjected unilaterally with either 4 mM strychnine (n = 7) or GABAzine (n = 7) to block glycine or GABA(A) receptors, respectively. Application of GABAzine caused an increase in overall phrenic amplitude during all three phases of respiration (inspiration, postinspiration, and expiration), while the increases caused by strychnine were most pronounced during postinspiration. Neither antagonist produced changes in inspiratory duration or respiratory rate. Power spectral analysis of inspiratory phrenic bursts showed that blockade of inhibition caused significant reduction in the relative power of MFO (GABA(A) and glycine receptors) and HFO (GABA(A) receptors only). In addition, analysis of the coherence between the firing of the ipsi- and contralateral phrenic nerves revealed that HFO coupling was significantly reduced by both antagonists and that of MFO was significantly reduced only by strychnine. We conclude that both GABA(A) and glycine receptors play critical roles in the organization of fast oscillations into MFO and HFO bands in the phrenic nerve, as well as in their bilateral coupling.
Topics: Animals; Biophysics; Decerebrate State; Electric Stimulation; Functional Laterality; GABA Antagonists; Glutamic Acid; Glycine; Glycine Agents; Laminectomy; Male; Neural Inhibition; Phrenic Nerve; Pyridazines; Rats; Rats, Sprague-Dawley; Respiration; Respiratory Center; Spectrum Analysis; Strychnine; Time Factors; gamma-Aminobutyric Acid
PubMed: 19225173
DOI: 10.1152/jn.91030.2008 -
Journal of Neurophysiology Dec 1997To further test the hypothesis that some fixed property of motoneurons determines their recruitment order, we quantified the variation in force threshold (FT) for...
To further test the hypothesis that some fixed property of motoneurons determines their recruitment order, we quantified the variation in force threshold (FT) for motoneurons recruited in muscle stretch reflexes in the decerebrate cat. Motor axons supplying the medial gastrocnemius (MG) muscle were penetrated with micropipettes and physiological properties of the motoneuron and its muscle fibers, i.e., the motor unit, were measured. FT, defined as the amount of MG force produced when the isolated motor unit was recruited, was measured from 20 to 93 consecutive stretch trials for 29 motor units. Trials were selected for limited variation in base force and rate of rise of force, which have been shown to covary with FT, and in peak stretch force, which gives some index of motor-pool excitability. Under these restricted conditions, large variation in FT would have been inconsistent with the hypothesis. Analysis of the variation in FT employed the coefficient of variation (CV), because of the tendency for FT variance and mean to increase together. We found that CV was distributed with a median value of 10% and with only 2 of 29 units exceeding 36%. Some of this variation was associated with measurement error and with intertrial fluctuations in base, peak, and the rate of change of muscle force. CV was not significantly correlated with motor-unit axonal conduction velocity, contraction time, or force. In three cases FT was measured simultaneously from two motor units in the same stretch trials. Changes in recruitment order were rarely observed (5 of 121 stretch trials), even when FT ranges for units in a pair overlapped. We suggest that the large variation in recruitment threshold observed in some earlier studies resulted not from wide variation in the recruitment ranking of motoneurons within one muscle, but rather from variation in the relative activity of different pools of motoneurons. Our findings are consistent with the hypothesis that recruitment order is determined by some fixed property of alpha-motoneurons and/or by some unvarying combination of presynaptic inputs that fluctuate in parallel.
Topics: Animals; Biomechanical Phenomena; Cats; Decerebrate State; Female; Male; Motor Neurons; Muscle, Skeletal; Reflex, Stretch
PubMed: 9405527
DOI: 10.1152/jn.1997.78.6.3077 -
American Journal of Physiology.... Jan 2020The exercise pressor reflex is composed of two components, namely the muscle mechanoreflex and the muscle metaboreflex. The afferents evoking the two components are...
The exercise pressor reflex is composed of two components, namely the muscle mechanoreflex and the muscle metaboreflex. The afferents evoking the two components are either thinly myelinated (group III) or unmyelinated (group IV); in combination they are termed "thin fiber afferents." The exercise pressor reflex is often studied in unanesthetized, decerebrate rats. However, the relationship between the magnitude of this reflex and the number of thin fiber afferents stimulated by muscle contraction is unknown. This lack of knowledge prompted us to test the hypothesis that the magnitude of the exercise pressor reflex was directly proportional to the amount of muscle mass activated. Muscle mechanoreceptors were stimulated by stretching the calcaneal tendon. Likewise, muscle metaboreceptors were stimulated by injecting lactic acid into the arterial supply of the hindlimb muscles. In addition, both muscle mechanoreceptors and metaboreceptors were stimulated by statically contracting the hindlimb muscles. We found that simultaneous bilateral (both hindlimbs) stimulation of thin fiber afferents with stretch, lactic acid, and static contraction evoked significantly greater pressor responses than did unilateral (one hindlimb) stimulation of these afferents. In addition, the magnitude of the pressor responses to bilateral simultaneous stimulation of thin fiber afferents evoked by stretch, lactic acid, and contraction was not significantly different from the magnitude of the sum of the pressor responses evoked by unilateral stimulation of these afferents by stretch, lactic acid, and contraction. We conclude that the magnitude of the exercise pressor reflex and its two components is dependent on the number of afferents stimulated.
Topics: Animals; Blood Pressure; Decerebrate State; Hindlimb; Male; Muscle Contraction; Muscle, Skeletal; Rats; Rats, Sprague-Dawley; Reflex
PubMed: 31664869
DOI: 10.1152/ajpregu.00263.2019 -
The Journal of Physiology Aug 2020Epidural electrical stimulation (ES) of the spinal cord restores/improves locomotion in patients. ES-evoked locomotor movements differ to some extent from the normal...
KEY POINTS
Epidural electrical stimulation (ES) of the spinal cord restores/improves locomotion in patients. ES-evoked locomotor movements differ to some extent from the normal ones. Operation of the locomotor network during ES is unknown. We compared the activity of individual spinal neurons during locomotion initiated by signals from the brainstem and by ES. We demonstrated that the spinal network generating locomotion under each of the two conditions is formed by the same neurons. A part of this network operates similarly under the two conditions, suggesting that it is essential for generation of locomotion under both conditions. Another part of this network operates differently under the two conditions, suggesting that it is responsible for differences in the movement kinematics observed under the two conditions.
ABSTRACT
Locomotion is a vital motor function for both animals and humans. Epidural electrical stimulation (ES) of the spinal cord is used to restore/improve locomotor movements in patients. However, operation of locomotor networks during ES has never been studied. Here we compared the activity of individual spinal neurons recorded in decerebrate cats of either sex during locomotion initiated by supraspinal commands (caused by stimulation of the mesencephalic locomotor region, MLR) and by ES. We found that under both conditions, the same neurons had modulation of their activity related to the locomotor rhythm, suggesting that the network generating locomotion under the two conditions is formed by the same neurons. About 40% of these neurons had stable modulation (i.e. small dispersion of their activity phase in sequential cycles), as well as a similar phase and shape of activity burst in MLR- and ES-evoked locomotor cycles. We suggest that these neurons form a part of the locomotor network that operates similarly under the two conditions, and are critical for generation of locomotion. About 23% of the modulated neurons had stable modulation only during MLR-evoked locomotion. We suggest that these neurons are responsible for some differences in kinematics of MLR- and ES-evoked locomotor movements. Finally, 25% of the modulated neurons had unstable modulation during both MLR- and ES-evoked locomotion. One can assume that these neurons contribute to maintenance of the excitability level of locomotor networks necessary for generation of stepping, or belong to postural networks, activated simultaneously with locomotor networks by both MLR stimulation and ES.
Topics: Animals; Brain Stem; Cats; Decerebrate State; Electric Stimulation; Humans; Locomotion; Mesencephalon; Spinal Cord
PubMed: 32445488
DOI: 10.1113/JP279460 -
Evocation of postural atonia and respiratory depression by pontine carbachol in the decerebrate rat.Brain Research Nov 1992To study mechanisms underlying the postural muscle atonia and respiratory depression associated with rapid eye movement (REM) sleep, the cholinergic agonist, carbachol,...
To study mechanisms underlying the postural muscle atonia and respiratory depression associated with rapid eye movement (REM) sleep, the cholinergic agonist, carbachol, was microinjected into the pontine reticular formation in decerebrate, spontaneously breathing rats. Carbachol injection led to a simultaneous depression of neck and tonic intercostal EMG activity (lasting 14.5 min +/- 7.6 (S.D.)) and a reduction of the respiratory rate. Phasic inspiratory intercostal activity was not consistently depressed. After a spontaneous recovery from the atonia and respiratory depression, subsequent carbachol injections at the same site produced similar responses. Thus, the decerebrate rat may provide a useful model for studies of the inhibitory neural mechanisms activated by the increased acetylcholine levels in the pons that occur in REM sleep. Pontine carbachol effects in rats differ from those described in cats in a manner analogous to differences in the patterns of natural REM sleep in these two species.
Topics: Acetylcholine; Animals; Carbachol; Decerebrate State; Depression, Chemical; Electromyography; Injections; Microinjections; Muscle Tonus; Pons; Posture; Rats; Rats, Sprague-Dawley; Respiration; Sleep, REM
PubMed: 1467945
DOI: 10.1016/0006-8993(92)91458-q -
American Journal of Physiology.... Oct 2002In supracollicular decerebrate paralyzed adult rats, neural respiration was monitored by bilateral phrenic recordings. In the study of respiratory cycle timing, the...
In supracollicular decerebrate paralyzed adult rats, neural respiration was monitored by bilateral phrenic recordings. In the study of respiratory cycle timing, the effects of vagal afferent input (lung inflation) on respiratory phase durations resembled those seen in decerebrate cats. 1) Withholding lung inflation during neural inspiration (I) produced lengthening of I phase duration by 46% (mean, n = 11). 2) Maintaining lung inflation during neural expiration (E) produced lengthening of E phase duration by 112% (mean, n = 4). In the study of fast rhythms in inspiratory discharges, phrenic nerve autospectra and bilateral (left-right) phrenic coherences in 16 rats revealed two types of fast rhythm: 1) high-frequency oscillation (HFO), which had significant coherence peaks (n = 9, range 106-160 Hz, mean 132 Hz); and 2) medium-frequency oscillation (MFO), which had autospectral peaks but no distinct coherence peaks (n = 11, range 46-96 Hz, mean 66 Hz). These rhythms resembled MFOs and HFOs in the decerebrate cat, but the modal frequency range was about twice as large. In addition, these frequency values differed markedly from the 20-40 Hz of the rhythms found in earlier studies in neonatal in vitro preparations; the difference may be due to developmental immaturity.
Topics: Afferent Pathways; Animals; Decerebrate State; Electrophysiology; Inhalation; Male; Oscillometry; Periodicity; Phrenic Nerve; Rats; Rats, Sprague-Dawley; Respiratory Physiological Phenomena; Time Factors; Vagus Nerve
PubMed: 12228063
DOI: 10.1152/ajpregu.00117.2002