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Journal of Neurophysiology Jun 2011Studies on brain stem respiratory neurons suggest that eupnea consists of three phases: inspiration, postinspiration, and expiration. However, it is not well understood...
Studies on brain stem respiratory neurons suggest that eupnea consists of three phases: inspiration, postinspiration, and expiration. However, it is not well understood how postinspiration is organized in the diaphragm, i.e., whether postinspiration differs in the crural and costal segments of the diaphragm and what the influence is of postinspiratory neurons on diaphragm function during eupnea. In this in vivo study we investigated the postinspiratory activity of the two diaphragm segments during eupnea and the changes in diaphragm function following modulation of eupnea. Postinspiratory neurons in the medulla were stereotaxically localized extracellularly and neurochemically stimulated. We used three types of preparations: precollicularly decerebrated unanesthetized cats and rats and anesthetized rats. In all preparations, during eupnea, postinspiratory activity was found in the crural but not in the costal diaphragm. When eupnea was discontinued in decerebrate cats in which stimulation in the nucleus retroambiguus induced activation of laryngeal or abdominal muscles, all postinspiratory activity in the crural diaphragm was abolished. In decerebrate rats, stimulation of the midbrain periaqueductal gray abolished postinspiration in the crural diaphragm but induced activation in the costal diaphragm. In anesthetized rats, stimulation of medullary postinspiratory neurons abolished the postinspiratory activity of the crural diaphragm. Vagal nerve stimulation in these rats increased the intensity of postinspiratory neuronal discharge in the solitary nucleus, leading to decreased activity of the crural diaphragm. These data demonstrate that three-phase breathing in the crural diaphragm during eupnea exists in vivo and that postinspiratory neurons have an inhibitory effect on crural diaphragm function.
Topics: Animals; Cats; Decerebrate State; Diaphragm; Electromyography; Female; Homocysteine; Male; Medulla Oblongata; Mesencephalon; Microinjections; Neurons; Rats; Rats, Sprague-Dawley; Respiration; Spectrum Analysis; Stimulation, Chemical; Vagus Nerve Stimulation
PubMed: 21451058
DOI: 10.1152/jn.00168.2011 -
American Journal of Physiology.... Sep 2008Hypothalamic neurons are regarded as essential for integrating thermal afferent information from skin and core and issuing commands to autonomic and behavioral effectors...
Hypothalamic neurons are regarded as essential for integrating thermal afferent information from skin and core and issuing commands to autonomic and behavioral effectors that maintain core temperature (T(c)) during cold exposure and for the control of energy expenditure more generally. Caudal brain stem neurons are necessary elements of the hypothalamic effector pathway and also are directly driven by skin and brain cooling. To assess whether caudal brain stem processing of thermal afferent signals is sufficient to drive endemic effectors for thermogenesis, heart rate (HR), T(c), and activity responses of chronic decerebrate (CD) and control rats adapted to 23 degrees C were compared during cold exposure (4, 8, or 12 degrees C) for 6 h. Other CDs and controls were exposed to 4 or 23 degrees C for 2 h, and tissues were processed for norepinephrine turnover (NETO), a neurochemical measure of sympathetic drive. Controls maintained T(c) for all temperatures. CDs maintained T(c) for the 8 and 12 degrees C exposures, but T(c) declined 2 degrees C during the 4 degrees C exposure. Cold exposure elevated HR in CDs and controls alike. Tachycardia magnitude correlated with decreases in environmental temperature for controls, but not CDs. Cold increased NETO in brown adipose tissue, heart, and some white adipose tissue pads in CDs and controls compared with their respective room temperature controls. These data demonstrate that, in neural isolation from the hypothalamus, cold exposure drives caudal brain stem neuronal activity and engages local effectors that trigger sympathetic energetic and cardiac responses that are comparable in many, but not in all, respects to those seen in neurologically intact rats.
Topics: Adipose Tissue, Brown; Adipose Tissue, White; Animals; Body Temperature; Body Temperature Regulation; Brain Stem; Chronic Disease; Cold Temperature; Decerebrate State; Denervation; Energy Metabolism; Heart Rate; Hypothalamus, Anterior; Male; Neural Pathways; Norepinephrine; Rats; Rats, Sprague-Dawley; Sympathetic Nervous System
PubMed: 18635447
DOI: 10.1152/ajpregu.90394.2008 -
The Journal of Physiology Dec 19951. Our purpose was to determine whether a pneumotaxic centre could be localized to the rostral pons in newborn rats. We recorded efferent activity of the phrenic nerve...
1. Our purpose was to determine whether a pneumotaxic centre could be localized to the rostral pons in newborn rats. We recorded efferent activity of the phrenic nerve in decerebrate, paralysed, vagotomized and ventilated rats, whose age varied from the day of birth to 22 days. 2. The rostral pontine tegmentum was ablated by aspiration and electrolytic lesions. Neuronal activities were blocked by microinjections of the glutamate antagonist MK-801 and were destroyed by the neurotoxins kainic acid and domoic acid. 3. Unilateral ablation or lesions of the pontine tegmentum caused a significant prolongation of the duration of the phrenic burst in animals of all ages. This duration increased further following contralateral destruction and apneusis was established. The period between phrenic bursts increased in most rats whereas peak phrenic height was not consistently altered. 4. Similar changes to those following physical ablations or lesions were recorded after microinjections of MK-801 or neurotoxins. 5. A common region of ablation, lesion and microinjection was the parabrachialis and Köllicker-Fuse nucleus. 6. Exposure to anoxia resulted in an alteration from apnoeusis to gasping. 7. We conclude that from the day of birth, rostral pontine pneumotaxic mechanisms play a significant role in the definition of eupnoea. Moreover, from the day of birth, rats can exhibit the classical ventilatory patterns of eupnoea, apneusis and gasping.
Topics: Age Factors; Animals; Animals, Newborn; Decerebrate State; Efferent Pathways; Female; Inhalation; Male; Phrenic Nerve; Pons; Rats; Rats, Sprague-Dawley; Respiration
PubMed: 8847649
DOI: 10.1113/jphysiol.1995.sp021074 -
Anesthesiology May 2002Isoflurane inhibits baroreflex control of heart rate (HR) by poorly understood mechanisms. The authors examined whether suprapontine central nervous system...
BACKGROUND
Isoflurane inhibits baroreflex control of heart rate (HR) by poorly understood mechanisms. The authors examined whether suprapontine central nervous system cardiovascular regulatory sites are required for anesthetic depression.
METHODS
The effects of isoflurane (1 and 2 rat minimum alveolar concentration [MAC]) on the baroreflex control of HR were determined in sham intact and midcollicular-transected decerebrate rats. Intravenous phenylephrine (0.2-12 microg/kg) and nitroprusside (1-60 microg/kg) were used to measure HR responses to peak changes in mean arterial pressure (MAP). Sigmoidal logistic curve fits to HR-MAP data assessed baroreflex sensitivity (HR/MAP), HR range, lower and upper HR plateau, and MAP at half the HR range (BP50). Four groups (two brain intact and two decerebrate) were studied before, during, and after isoflurane. To assess sympathetic and vagal contributions to HR baroreflex, beta-adrenoceptor (1 mg/kg atenolol) or muscarinic (0.5 mg/kg methyl atropine) antagonists were administered systemically.
RESULTS
Decerebration did not alter resting MAP and HR or baroreflex parameters. Isoflurane depressed baroreflex slope and HR range in brain-intact and decerebrate rats. In both groups, 1 MAC reduced HR range by depressing peak reflex tachycardia. Maximal reflex bradycardia during increases in blood pressure was relatively preserved. Atenolol during 1 MAC did not alter maximum reflex tachycardia. In contrast, atropine during 1 MAC fully blocked reflex bradycardia. Therefore, 1 MAC predominantly depresses sympathetic components of HR baroreflex. Isoflurane at 2 MAC depressed both HR plateaus and decreased BP50 in both groups.
CONCLUSIONS
Isoflurane depresses HR baroreflex control by actions that do not require suprapontine central nervous system sites. Isoflurane actions seem to inhibit HR baroreflex primarily by the sympathetic nervous system.
Topics: Adrenergic beta-Antagonists; Algorithms; Anesthetics, Inhalation; Animals; Atenolol; Atropine; Autonomic Pathways; Baroreflex; Blood Gas Analysis; Decerebrate State; Heart Rate; Hematocrit; Hemodynamics; Isoflurane; Male; Muscarinic Antagonists; Potassium; Rats; Rats, Sprague-Dawley; Sodium
PubMed: 11981163
DOI: 10.1097/00000542-200205000-00026 -
British Journal of Pharmacology and... Dec 1962The effect of 2,4-di(diethylamino)-6-(2-phenylacetylhydrazino)-1,3,5-triazine (Ciba 28882-Ba) injected intravenously on the activity of de-efferented muscle spindles of...
The effect of 2,4-di(diethylamino)-6-(2-phenylacetylhydrazino)-1,3,5-triazine (Ciba 28882-Ba) injected intravenously on the activity of de-efferented muscle spindles of the tibialis anterior and extensor digitorum longus muscles of anaesthetized cats, and on gamma-motoneurones of decerebrate cats, was investigated. The drug depressed both the static activity of muscle spindles and the spontaneous activity of gamma-motoneurones. In contrast, the response of muscle spindles to rapid stretch was not affected. The effect of 28882-Ba on the activity of the muscle spindles resembled that of progressive unloading or shortening of the muscle. 28882-Ba antagonized excitation of the muscle spindle by suxamethonium. The effect of 28882-Ba on the response of the gamma-motoneurones to various driving stimuli was not predictable.
Topics: Animals; Cats; Decerebrate State; Motor Neurons, Gamma; Muscle Relaxants, Central; Muscle Spindles; Muscle, Skeletal; Muscles; Nerve Endings; Succinylcholine; Triazines
PubMed: 13970329
DOI: 10.1111/j.1476-5381.1962.tb01442.x -
Neurourology and Urodynamics Nov 2018To assess bladder smooth muscle function and innervation after long-term lower spinal root transection in canines.
AIMS
To assess bladder smooth muscle function and innervation after long-term lower spinal root transection in canines.
METHODS
Thirteen female mixed-breed hound dogs underwent bladder decentralization, which included transection of all sacral dorsal and ventral roots caudal to L7 and hypogastric nerves, bilaterally (n = 3); all sacral roots and hypogastric nerves plus transection of L7 dorsal roots, bilaterally (n = 4); or a sham operation (n = 6). At a year after initial surgery, bladder function was assessed in vivo by stimulation of the pelvic plexus. The bladder tissue was harvested for ex vivo smooth muscle contractility studies. Remaining bladder was evaluated for nerve morphology immunohistochemically using neuronal marker PGP9.5, apoptotic activity using terminal deoxynucleotidyl transferase dUTP nick end labeling, and histopathology using a hematoxylin and eosin stain.
RESULTS
Sacral root decentralization did not reduce maximum strength of pelvic plexus stimulation-induced bladder contraction, although long-term sacral dorsal and ventral root plus L7 dorsal root transection significantly decreased contraction strength. Electric field stimulation-induced contractions of the detrusor from all decentralized animals were preserved, compared to controls. Viable nerves and intramural ganglia were visualized in the bladder wall, regardless of group. There was no difference in amount of apoptosis in bladder smooth muscle between groups.
CONCLUSION
Bladder smooth muscle cells maintain their function after long-term bladder decentralization. While pelvic plexus-induced bladder contractions were less robust at 1 year after lower spinal root transection, the absence of atrophy and preservation of at least some nerve activity may allow for successful surgical reinnervation after long-term injury.
Topics: Animals; Decerebrate State; Dogs; Electric Stimulation; Female; Hypogastric Plexus; In Situ Nick-End Labeling; Muscle Contraction; Muscle, Smooth; Nerve Regeneration; Spinal Nerve Roots; Urinary Bladder
PubMed: 30024057
DOI: 10.1002/nau.23765 -
Journal of Neurophysiology Mar 2010Hip position and loading of limb extensors are major sensory cues for the initiation and duration of different phases during walking. Although these inputs have pathways...
Hip position and loading of limb extensors are major sensory cues for the initiation and duration of different phases during walking. Although these inputs have pathways projecting to the locomotor rhythm generator, their effects may vary in different parts of the locomotor cycle. In the present study, the plantaris (Pl), sartorius (Sart), rectus femoris (RF), and caudal gluteal (cGlu) nerves were stimulated at group I and/or group II strength during spontaneous fictive locomotion in 16 adult decerebrate cats. These nerves supply muscles that extend the ankle (Pl), flex the hip (Sart, RF), or extend the hip (cGlu). Stimuli were given at six epochs of the locomotor cycle to evaluate when they access the rhythm generator. Group I afferents from Pl nerve always reset the locomotor rhythm; stimulation during extension prolonged cycle period and extension phase duration, while stimulation during flexion terminated flexion and initiated extension. On the other hand, stimulating RF and cGlu nerves only produced significant effects on the rhythm in precise epochs, particularly during mid-flexion and/or mid- to late extension. Stimulating the Sart nerve produced complex effects on the rhythm that were not distributed evenly to all extensor motor pools. The most consistent effect was reduced flexion phase duration with stimulation during flexion, particularly at group II strength, and prolongation of the extension phase but only in late extension. That hip muscle afferents reset the rhythm in only specific epochs of the locomotor cycle suggests that the rhythm generator operates with several subdivisions to determine phase and cycle durations.
Topics: Animals; Cats; Data Interpretation, Statistical; Decerebrate State; Electric Stimulation; Hindlimb; Hip; Instinct; Locomotion; Muscle, Skeletal; Neurons, Afferent
PubMed: 20089809
DOI: 10.1152/jn.01028.2009 -
The Journal of Physiology Oct 1983In high decerebrate unanaesthetized cats (pre-collicular/pre-mamillary) which developed spontaneous co-ordinated locomotor activity, ventilation, breathing pattern,...
In high decerebrate unanaesthetized cats (pre-collicular/pre-mamillary) which developed spontaneous co-ordinated locomotor activity, ventilation, breathing pattern, phrenic nerve, external and internal intercostal electromyogram (e.m.g.) activities were examined. Locomotion was also induced by electrical stimulation of the subthalamic locomotor region and in a few cases the mesencephalic locomotor region. Quadriceps muscle e.m.g. was used to monitor locomotor activity. Spontaneous locomotor activity was associated with an immediate increase in ventilation and shift of the ventilatory CO2 response curve to the left. Tidal volume was smaller and respiratory rate larger at any given level of ventilation during spontaneous locomotion. Increases in respiratory rate were due to reductions in both inspiratory and expiratory duration. Upon cessation of locomotion, these changes abruptly returned to control values. Within the first one or two walking steps of spontaneous locomotor activity, the rate of rise of phrenic activity increased slightly while peak phrenic activity remained relatively constant; peak internal intercostal activity increased markedly while peak external intercostal activity decreased. Similar changes in ventilation, phrenic, external and internal intercostal activities were observed in association with locomotion induced by stimulation within the subthalamic or mesencephalic locomotor regions. In contrast to spontaneous locomotor activity, however, increases in both external and internal intercostal activities were often observed. Peak amplitudes of both external and internal intercostal activities increased linearly with increasing levels of end-tidal PCO2 during rest and during locomotion. However, at any given level of PCO2 peak external intercostal activity was smaller and peak internal intercostal activity larger during locomotion than at rest. With increasing peak quadriceps e.m.g. activity at a constant walking rate, external intercostal activity was progressively inhibited while internal intercostal activity was progressively enhanced. No consistent change in peak phrenic activity was observed with changes in peak quadriceps activity. With increasing walking rate at a constant peak quadriceps e.m.g., peak phrenic and peak internal intercostal activities progressively increased and peak amplitude of external intercostal activity (which was inhibited below the activity observed at rest) also progressively increased. The virtually simultaneous changes in quadriceps activity and respiratory motor activities suggest that the increase in ventilation at exercise onset is neurally mediated. Furthermore, these results suggest that the motor pathways to both the spinal locomotor pattern generators and the pattern-controlling mechanisms for respiration are driven in parallel to provide a quantitative relationship between respiratory motor output and locomotor activity. The functional significance of the alterations in respiratory pattern and participation of the different respiratory muscles is discussed.
Topics: Animals; Cats; Decerebrate State; Electric Stimulation; Electromyography; Intercostal Nerves; Motor Activity; Muscles; Phrenic Nerve; Respiration; Respiratory Function Tests; Thigh
PubMed: 6644612
DOI: 10.1113/jphysiol.1983.sp014878 -
Journal of Neurophysiology Sep 2005An obstacle contacting the dorsal surface of a cat's hind foot during the swing phase of locomotion evokes a reflex (the stumbling corrective reaction) that lifts the... (Comparative Study)
Comparative Study
An obstacle contacting the dorsal surface of a cat's hind foot during the swing phase of locomotion evokes a reflex (the stumbling corrective reaction) that lifts the foot and extends the ankle to avoid falling. We show that the same sequence of ipsilateral hindlimb motoneuron activity can be evoked in decerebrate cats during fictive locomotion. As recorded in the peripheral nerves, twice threshold intensity stimulation of the cutaneous superficial peroneal (SP) nerve during the flexion phase produced a very brief excitation of ankle flexors (e.g., tibialis anterior and peroneus longus) that was followed by an inhibition for the duration of the stimulus train (10-25 shocks, 200 Hz). Extensor digitorum longus was always, and hip flexor (sartorius) activity was sometimes, inhibited during SP stimulation. At the same time, knee flexor and the normally quiescent ankle extensor motoneurons were recruited (mean latencies 4 and 16 ms) with SP stimulation during fictive stumbling correction. After the stimulus train, ankle extensor activity fell silent, and there was an excitation of hip, knee, and ankle flexors. The ongoing flexion phase was often prolonged. Hip extensors were also recruited in some fictive stumbling trials. Only the SP nerve was effective in evoking stumbling correction. Delivered during extension, SP stimulus trains increased ongoing extensor motoneuron activity as well as increasing ipsilateral hip, knee, and ankle hindlimb flexor activity in the subsequent step cycle. The fictive stumbling corrective reflex seems functionally similar to that evoked in intact, awake animals and involves a fixed pattern of short-latency reflexes as well as actions evoked through the lumbar circuitry responsible for the generation of rhythmic alternating locomotion.
Topics: Animals; Cats; Decerebrate State; Dose-Response Relationship, Radiation; Electric Stimulation; Electromyography; Functional Laterality; Locomotion; Lower Extremity; Motor Neurons; Neural Inhibition; Peroneal Nerve; Reaction Time; Reflex; Time Factors
PubMed: 15917325
DOI: 10.1152/jn.00175.2005 -
Experimental Neurology Oct 1995We have studied the locomotor development of kittens that received complete low thoracic spinal cord transections and embryonic spinal cord transplants as newborns....
We have studied the locomotor development of kittens that received complete low thoracic spinal cord transections and embryonic spinal cord transplants as newborns. Embryonic spinal cord (E21-E26) transplanted into the site of a transection integrated well with the host spinal cord and promoted the development of overground locomotion. Spinalized kittens with transplants were first distinguished from spinalized kittens during the 2nd and 3rd postnatal weeks when kittens with transplants positioned their hindlimbs underneath their bodies which promoted support of the hindquarters. By postnatal Week 6, kittens with transplants exhibited overground locomotion characterized by full weight support and moderate balance control. By 20 weeks of age, as many as 96% of the step cycles showed full weight support and as few as 2% of the step cycles were interrupted by a fall. Most kittens also showed coordination between the forelimbs and the hindlimbs. They differed from normal in the precocious onset of reflex stepping and in the less precise interlimb coordination and more precarious balance during overground locomotion. The overground locomotor performance of kittens with transplants greatly exceeded that of spinal kittens without transplants since few spinalized kittens showed any full-weight-supported step cycles and none showed coordination between the forelimbs and the hindlimbs. In the absence of a transplant, no fibers could grow across the lesion site. In the presence of a transplant, fibers grew across the lesion site and established anatomical connectivity with the host. Host segmental systems identified by the presence of calcitonin gene-related peptide- and substance P-immunoreactive fibers were found throughout the transplants. Descending host systems of supraspinal origin were identified by serotonin- and dopamine beta-hydroxylase-immunoreactive fibers throughout the transplants. The growth of supraspinal axons into the transplant, and in one case into the caudal host spinal cord, provided a possible anatomical basis for the development of coordinated overground locomotion.
Topics: Age Factors; Animals; Animals, Newborn; Behavior, Animal; Cats; Decerebrate State; Female; Hindlimb; Locomotion; Male; Spinal Cord
PubMed: 7589324
DOI: 10.1006/exnr.1995.1072