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Titolo:
Activity of hindlimb motor units during locomotion in the conscious rat
Autore:
Gorassini, M; Eken, T; Bennett, DJ; Kiehn, O; Hultborn, H;
Indirizzi:
Univ Oslo, Inst Neurophysiol, N-0317 Oslo, Norway Univ Oslo Oslo Norway N-0317 slo, Inst Neurophysiol, N-0317 Oslo, Norway Univ Copenhagen, Dept Med Physiol, Sect Neurophysiol, DK-2200 Copenhagen N, Denmark Univ Copenhagen Copenhagen Denmark N siol, DK-2200 Copenhagen N, Denmark
Titolo Testata:
JOURNAL OF NEUROPHYSIOLOGY
fascicolo: 4, volume: 83, anno: 2000,
pagine: 2002 - 2011
SICI:
0022-3077(200004)83:4<2002:AOHMUD>2.0.ZU;2-2
Fonte:
ISI
Lingua:
ENG
Soggetto:
MEDIAL GASTROCNEMIUS-MUSCLE; TIBIALIS ANTERIOR MUSCLE; MOTONEURONS IN-VITRO; LUMBAR MOTONEURONS; HISTOCHEMICAL PROPERTIES; LATERAL GASTROCNEMIUS; FICTIVE LOCOMOTION; DECEREBRATE CATS; SPINAL-CORD; PATTERNS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
37
Recensione:
Indirizzi per estratti:
Indirizzo: Gorassini, M Univ Alberta, Fac Rehabil Med, Div Neurosci, 3-48 Corbett Hall, Edmonton, AB T6G 2G4, Canada Univ Alberta 3-48 Corbett Hall Edmonton AB Canada T6G 2G4 ada
Citazione:
M. Gorassini et al., "Activity of hindlimb motor units during locomotion in the conscious rat", J NEUROPHYS, 83(4), 2000, pp. 2002-2011

Abstract

This paper compares the activity of hindlimb motor units from muscles mainly composed of fast-twitch muscle fibers (medial and lateral gastroenemius:MG/LG, tibialis anterior: TA) to motor units from a muscle mainly composedof slow-twitch muscle fibers (soleus: SOL) during unrestrained walking in the conscious rat. Several differences in the activation profiles of motor units from these two groups of muscles were observed. For example, motor units from fast muscles (e.g., MG/LG and TA) fired at very high mean frequencies of discharge, ranging from 60 to 100 Hz, and almost always were recruited with initial doublets or triplets, i.e., initial frequencies greater than or equal to 100 Hz. In contrast, the majority of SOL units fired at much lower mean rates of discharge, approximate to 30 Hz, and had initial frequencies of only 30-60 Hz (i.e., there were no initial doublets/triplets greater than or equal to 100 Hz). Thus the presence of initial doublet or triplets was dependent on the intrinsic properties of the motor unit, i.e., faster units were recruited with a doublet/triplet more often than slower units. Moreover, in contrast to units from the slow SOL muscle, the activity of single motor units from the fast MG/LG muscle, especially units recruited midway or near the end of a locomotor burst, was unrelated to the activity ofthe remainder of the motoneuron pool, as measured by the corresponding gross-electromyographic (EMG) signal. This dissociation of activity was suggested to arise from a compartmentalized recruitment of the MG/LG motoneuron pool by the rhythm-generating networks of the spinal cord. In contrast, whencomparing the rate modulation of simultaneously recorded motor units within a single LG muscle compartment, the frequency profiles of unit pairs weremodulated in a parallel fashion. This suggested that the parent motoneurons were responsive to changes in synaptic inputs during unrestrained walking, unlike the poor rate modulation that occurs during locomotion induced from brain stem stimulation. In summary, data from this study provide evidencethat the firing behavior of motor units during unrestrained walking is influenced by both the intrinsic properties of the parent motoneuron and by synaptic inputs from the locomotor networks of the spinal cord. in addition, it also provides the first extensive description of motor-unit activity from different muscles during unrestrained walking in the conscious rat.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 31/03/20 alle ore 10:20:28