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  • American Physiological Society  (15)
  • 1
    Online Resource
    Online Resource
    American Physiological Society ; 1982
    In:  American Journal of Physiology-Regulatory, Integrative and Comparative Physiology Vol. 242, No. 3 ( 1982-03-01), p. R220-R226
    In: American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, American Physiological Society, Vol. 242, No. 3 ( 1982-03-01), p. R220-R226
    Abstract: The effect of ventromedial (VMN) or basolateral (LHA) hypothalamic electrical stimulation on glucose and hormone production was examined in conscious and anesthetized male rats. Barbiturate treatment alone led to large increases of corticosterone and smaller but significant increases of glucose, insulin, and glucagon. When hypothalamic stimulation was combined with anesthesia, interactions between the hypothalamic sites and the awake-anesthetized conditions were observed. This was most evident with LHA placements, as awake rats exhibited mild hypoglycemia and hypoglucagonemia in response to low-level (approximately 10 microA rms) current, but no effects on these values were seen with VMN electrodes. With barbiturate anesthesia, the same level of stimulation led to severe hyperglycemia in both VMN and LHA rats and a mild hyperglucagonemia in the LHA group. No consistent effects of stimulation on immunoreactive insulin or corticosterone were detected at either hypothalamic site or in any anesthesia condition. The present results point out the important role anesthetics may play in studies defining functional aspects of the hypothalamus. Furthermore, our inability to elicit consistent autonomic responses with electrical stimulation, when compared with the effectiveness of both metabolic agents and pharmacologic stimuli, suggests that the sites integrating autonomic function may be diffusely distributed over the basal diencephalon.
    Type of Medium: Online Resource
    ISSN: 0363-6119 , 1522-1490
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1982
    detail.hit.zdb_id: 1477297-8
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    American Physiological Society ; 1986
    In:  Journal of Neurophysiology Vol. 55, No. 2 ( 1986-02-01), p. 375-401
    In: Journal of Neurophysiology, American Physiological Society, Vol. 55, No. 2 ( 1986-02-01), p. 375-401
    Abstract: Recordings were made from single units in the medullary reticular formation (MRF) between AP-4.2 and AP-12.9 and from the midline to 3.7 mm lateral in chronically prepared, unrestrained cats walking on a treadmill. Recordings were made with rigid microelectrodes held in a microdrive, and reticulospinal neurons were identified by antidromic stimulation of their axons through microwires chronically implanted into the spinal cord at the L2 level. Electromyograms (EMGs) were recorded from flexor and extensor muscles of the fore- and hindlimbs as well as from back and neck muscles. In total, 295 cells were recorded from 40 penetrations in 4 cats; 252 of these cells were recorded from the more medial regions of the reticular formation encompassing the gigantocellular, magnocellular, and lateral tegmental fields; 38.5% of these (97/252) were antidromically identified from the spinal cord. The remaining 43 neurons (43/295) were recorded from a more lateral and ventral position. These medial and ventrolateral groups of neurons differed not only in position but also in aspects of their discharge during locomotion. Rank-ordered raster displays, triggered from the onset of each recorded muscle, were used to correlate neuronal and muscular activity. The discharge rate of 31% of the reticulospinal neurons (30/97) was modulated once or twice in each step cycle and was strictly related to one or more of the recorded EMGs (EMG-related neurons) on the basis of the pattern of discharge. The discharge of 33/97 (34%) of the neurons was modulated at the periodicity of the locomotor rhythm but could not be correlated with any of the recorded EMGs (locomotor-related cells), whereas the remaining 34/97 neurons (35%) were either silent, fired tonically, or were not related to the locomotor pattern (unrelated cells). Of the EMG-related neurons 27% were related to flexor muscles and the remaining 63% to extensor muscle activity. The discharge pattern of all except two of the flexor-related neurons was correlated with hindlimb muscle activity, whereas that of the extensor-related neurons was correlated almost equally with fore- and hindlimb muscles. Correlations were found with muscles lying both ipsilaterally and contralaterally to the site of the recordings. Although the locomotor-related neurons showed no preferential relation with any of the recorded EMGs, a comparison of the depth of modulation of their discharge measured from postevent histograms suggested that more of these cells were related to the forelimb than to the hindlimb.(ABSTRACT TRUNCATED AT 400 WORDS)
    Type of Medium: Online Resource
    ISSN: 0022-3077 , 1522-1598
    RVK:
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1986
    detail.hit.zdb_id: 80161-6
    detail.hit.zdb_id: 1467889-5
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  • 3
    Online Resource
    Online Resource
    American Physiological Society ; 1999
    In:  Journal of Neurophysiology Vol. 82, No. 2 ( 1999-08-01), p. 1074-1077
    In: Journal of Neurophysiology, American Physiological Society, Vol. 82, No. 2 ( 1999-08-01), p. 1074-1077
    Abstract: An in vitro brain stem–spinal cord preparation from an adult urodele ( Pleurodeles waltl) was developed in which two fictive rhythmic motor patterns were evoked by bath application of N-methyl-d-aspartate (NMDA; 2.5–10 μM) with d-serine (10 μM). Both motor patterns displayed left-right alternation. The first pattern was characterized by cycle periods ranging between 2.4 and 9.0 s (4.9 ± 1.2 s, mean ± SD) and a rostrocaudal propagation of the activity in consecutive ventral roots. The second pattern displayed longer cycle periods (8.1–28.3 s; 14.2 ± 3.6 s) with a caudorostral propagation. The two patterns were inducible after a spinal transection at the first segment. Preliminary experiments on small pieces of spinal cord further suggested that the ability for rhythm generation is distributed along the spinal cord of this preparation. This study shows that the in vitro brain stem–spinal cord preparation from Pleurodeles waltl may be a useful model to study the mechanisms underlying the different axial motor patterns and the flexibility of the neural networks involved.
    Type of Medium: Online Resource
    ISSN: 0022-3077 , 1522-1598
    RVK:
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1999
    detail.hit.zdb_id: 80161-6
    detail.hit.zdb_id: 1467889-5
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  • 4
    Online Resource
    Online Resource
    American Physiological Society ; 2005
    In:  Journal of Neurophysiology Vol. 93, No. 4 ( 2005-04), p. 2127-2141
    In: Journal of Neurophysiology, American Physiological Society, Vol. 93, No. 4 ( 2005-04), p. 2127-2141
    Abstract: Substance P initiates locomotion when injected in the brain stem of mammals. This study examined the possible role of this peptide on the supraspinal locomotor command system in lampreys. Substance P was bath applied or locally injected into an in vitro isolated brain stem, and the effects of the drug were examined on reticulospinal cells and on the occurrence of swimming in a semi-intact preparation. Bath applications of substance P induced sustained depolarizations occurring rhythmically in intracellularly recorded reticulospinal cells. Spiking activity was superimposed on the depolarizations and swimming was induced. The sustained depolarizations were abolished by tetrodotoxin, and substance P did not affect the membrane resistance of reticulospinal cells nor their firing properties, suggesting that it did not directly effect reticulospinal cells. To establish where the effects were exerted, successive lesions of the brain stem were made as well as local applications of the drug in the brain stem. Removing the mesencephalon abolished the sustained depolarizations, whereas large ejections of the drug in the mesencephalon excited reticulospinal cells and elicited bouts of swimming. More local injections into the mesencephalic locomotor region (MLR) also elicited swimming. After an injection of substance P, the current threshold needed to induce locomotion by MLR stimulation was decreased, and the size of the postsynaptic responses of reticulospinal cells to MLR stimulation was increased. Substance P also reduced the frequency of miniature spontaneous postsynaptic currents in reticulospinal cells. Taken together, these results suggest that substance P plays a neuromodulatory role on the brain stem locomotor networks of lampreys.
    Type of Medium: Online Resource
    ISSN: 0022-3077 , 1522-1598
    RVK:
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2005
    detail.hit.zdb_id: 80161-6
    detail.hit.zdb_id: 1467889-5
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  • 5
    Online Resource
    Online Resource
    American Physiological Society ; 2007
    In:  Journal of Neurophysiology Vol. 97, No. 5 ( 2007-05), p. 3181-3192
    In: Journal of Neurophysiology, American Physiological Society, Vol. 97, No. 5 ( 2007-05), p. 3181-3192
    Abstract: In lampreys, brain stem reticulospinal (RS) neurons constitute the main descending input to the spinal cord and activate the spinal locomotor central pattern generators. Cholinergic nicotinic inputs activate RS neurons, and consequently, induce locomotion. Cholinergic muscarinic agonists also induce locomotion when applied to the brain stem of birds. This study examined whether bath applications of muscarinic agonists could activate RS neurons and initiate motor output in lampreys. Bath applications of 25 μM muscarine elicited sustained, recurring depolarizations (mean duration of 5.0 ± 0.5 s recurring with a mean period of 55.5 ± 10.3 s) in intracellularly recorded rhombencephalic RS neurons. Calcium imaging experiments revealed that muscarine induced oscillations in calcium levels that occurred synchronously within the RS neuron population. Bath application of TTX abolished the muscarine effect, suggesting the sustained depolarizations in RS neurons are driven by other neurons. A series of lesion experiments suggested the caudal half of the rhombencephalon was necessary. Microinjections of muscarine (75 μM) or the muscarinic receptor (mAchR) antagonist atropine (1 mM) lateral to the rostral pole of the posterior rhombencephalic reticular nucleus induced or prevented, respectively, the muscarinic RS neuron response. Cells immunoreactive for muscarinic receptors were found in this region and could mediate this response. Bath application of glutamatergic antagonists (6-cyano-7-nitroquinoxaline-2,3-dione/d-2-amino-5-phosphonovaleric acid) abolished the muscarine effect, suggesting that glutamatergic transmission is needed for the effect. Ventral root recordings showed spinal motor output coincides with RS neuron sustained depolarizations. We propose that unilateral mAchR activation on specific cells in the caudal rhombencephalon activates a circuit that generates synchronous sustained, recurring depolarizations in bilateral populations of RS neurons.
    Type of Medium: Online Resource
    ISSN: 0022-3077 , 1522-1598
    RVK:
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2007
    detail.hit.zdb_id: 80161-6
    detail.hit.zdb_id: 1467889-5
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  • 6
    Online Resource
    Online Resource
    American Physiological Society ; 2006
    In:  Physiological Reviews Vol. 86, No. 1 ( 2006-01), p. 89-154
    In: Physiological Reviews, American Physiological Society, Vol. 86, No. 1 ( 2006-01), p. 89-154
    Abstract: Locomotion results from intricate dynamic interactions between a central program and feedback mechanisms. The central program relies fundamentally on a genetically determined spinal circuitry (central pattern generator) capable of generating the basic locomotor pattern and on various descending pathways that can trigger, stop, and steer locomotion. The feedback originates from muscles and skin afferents as well as from special senses (vision, audition, vestibular) and dynamically adapts the locomotor pattern to the requirements of the environment. The dynamic interactions are ensured by modulating transmission in locomotor pathways in a state- and phase-dependent manner. For instance, proprioceptive inputs from extensors can, during stance, adjust the timing and amplitude of muscle activities of the limbs to the speed of locomotion but be silenced during the opposite phase of the cycle. Similarly, skin afferents participate predominantly in the correction of limb and foot placement during stance on uneven terrain, but skin stimuli can evoke different types of responses depending on when they occur within the step cycle. Similarly, stimulation of descending pathways may affect the locomotor pattern in only certain phases of the step cycle. Section ii reviews dynamic sensorimotor interactions mainly through spinal pathways. Section iii describes how similar sensory inputs from the spinal or supraspinal levels can modify locomotion through descending pathways. The sensorimotor interactions occur obviously at several levels of the nervous system. Section iv summarizes presynaptic, interneuronal, and motoneuronal mechanisms that are common at these various levels. Together these mechanisms contribute to the continuous dynamic adjustment of sensorimotor interactions, ensuring that the central program and feedback mechanisms are congruous during locomotion.
    Type of Medium: Online Resource
    ISSN: 0031-9333 , 1522-1210
    RVK:
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2006
    detail.hit.zdb_id: 1471693-8
    SSG: 12
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  • 7
    Online Resource
    Online Resource
    American Physiological Society ; 1992
    In:  American Journal of Physiology-Endocrinology and Metabolism Vol. 263, No. 3 ( 1992-09-01), p. E550-E555
    In: American Journal of Physiology-Endocrinology and Metabolism, American Physiological Society, Vol. 263, No. 3 ( 1992-09-01), p. E550-E555
    Abstract: Glucoregulation and body composition were examined in 3-mo-old C57BL/6 ob/ob mice 6 wk after streptozotocin (STZ) or STZ plus adrenalectomy. STZ depressed somatic growth in ob/ob mice but did not cause hyperglycemia until immunoreactive insulin (IRI) was 40% (100 microU/ml) that of intact ob/ob mice. When IRI approached that of lean mice (40 microU/ml), ob/ob mice displayed severe hyperglycemia (800+ mg/dl) and other sequelae of type I diabetes but still maintained the same 50% body fat as untreated obese mice. In contrast, STZ diabetes in lean mice caused disproportionate reductions in body fat. Adrenalectomy before STZ led to the same insulinopenia, depressed growth, and hyperglycemia as STZ alone, but, after combined treatment, percent body fat declined in proportion to IRI. Thus a subgroup of severely diabetic adrenalectomized STZ obese mice with very low IRI (20 microU/ml) had body fat contents and fat-free masses equal to those of weight-matched lean mice. The data suggest that hypercorticoidism rather than hyperinsulinemia is largely responsible for obesity in ob/ob mice. However, in the absence of adrenal glucocorticoids, or perhaps with just their normalization, hyperinsulinemia appears necessary for maintaining excessive body energy stores.
    Type of Medium: Online Resource
    ISSN: 0193-1849 , 1522-1555
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1992
    detail.hit.zdb_id: 1477331-4
    SSG: 12
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  • 8
    Online Resource
    Online Resource
    American Physiological Society ; 1988
    In:  American Journal of Physiology-Regulatory, Integrative and Comparative Physiology Vol. 255, No. 5 ( 1988-11-01), p. R787-R793
    In: American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, American Physiological Society, Vol. 255, No. 5 ( 1988-11-01), p. R787-R793
    Abstract: Carcass composition was determined in intact and adrenalectomized (ADX) ob/ob mice after 6 wk of food restriction from weaning (21 days). Diets (2.6 or 3.2 g/day) led to reduced weight gain in intact ob/ob mice, but fat deposition was still greater, and lean growth was less than isocalorically fed lean mice. When diet was combined with ADX, obese mice fed 3.2 g/day had rates of fat-free body growth equal to ad libitum-fed lean mice but still gained more weight and deposited more fat. With 2.6 g/day, however, body weight gain, fat deposition, fat-free body growth, and protein deposition were all similar to intact lean mice receiving the same diet. Neither diet nor diet combined with ADX improved the defective thermoregulation of obese mice tested at 23 degrees C, 8 degrees C, or in response to food deprivation or food ingestion. Together, diet and adrenalectomy reduced blood glucose and insulin levels in ob/ob mice, and with the 2.6 g/day diet, the values of each were the same as littermate lean controls. The present results indicate that adrenal glucocorticoids are necessary for maintaining elevated fat deposition at the expense of lean body growth in dieted ob/ob mice, whereas hyperphagia, defective thermoregulation, energy efficiency, and diabetes are still expressed after surgery.
    Type of Medium: Online Resource
    ISSN: 0363-6119 , 1522-1490
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1988
    detail.hit.zdb_id: 1477297-8
    SSG: 12
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  • 9
    Online Resource
    Online Resource
    American Physiological Society ; 2023
    In:  Journal of Neurophysiology Vol. 130, No. 2 ( 2023-08-01), p. 401-416
    In: Journal of Neurophysiology, American Physiological Society, Vol. 130, No. 2 ( 2023-08-01), p. 401-416
    Abstract: The ability to generate and control locomotor movements depends on complex interactions between many areas of the nervous system, the musculoskeletal system, and the environment. How the nervous system manages to accomplish this task has been the subject of investigation for more than a century. In vertebrates, locomotion is generated by neural networks located in the spinal cord referred to as central pattern generators. Descending inputs from the brain stem initiate, maintain, and stop locomotion as well as control speed and direction. Sensory inputs adapt locomotor programs to the environmental conditions. This review presents a comparative and historical overview of some of the neural mechanisms underlying the control of locomotion in vertebrates. We have put an emphasis on spinal mechanisms and descending control.
    Type of Medium: Online Resource
    ISSN: 0022-3077 , 1522-1598
    RVK:
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2023
    detail.hit.zdb_id: 80161-6
    detail.hit.zdb_id: 1467889-5
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  • 10
    Online Resource
    Online Resource
    American Physiological Society ; 1974
    In:  American Journal of Physiology-Legacy Content Vol. 227, No. 3 ( 1974-09-01), p. 697-702
    In: American Journal of Physiology-Legacy Content, American Physiological Society, Vol. 227, No. 3 ( 1974-09-01), p. 697-702
    Type of Medium: Online Resource
    ISSN: 0002-9513
    RVK:
    RVK:
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1974
    detail.hit.zdb_id: 1477334-X
    detail.hit.zdb_id: 2065807-2
    detail.hit.zdb_id: 1477287-5
    detail.hit.zdb_id: 1477308-9
    detail.hit.zdb_id: 1477297-8
    detail.hit.zdb_id: 1477331-4
    detail.hit.zdb_id: 1477300-4
    detail.hit.zdb_id: 1477329-6
    SSG: 12
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