The respiratory drive to thoracic motoneurones in the cat and its relation to the connections from expiratory bulbospinal neurones
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The respiratory drive to thoracic motoneurones in the cat and its relation to the connections from expiratory bulbospinal neurones. / Saywell, S A; Anissimova, N P; Ford, T W; Meehan, Claire Francesca; Kirkwood, P A.
In: Journal of Physiology, Vol. 579, No. Pt 3, 2007, p. 765-82.Research output: Contribution to journal › Journal article › Research › peer-review
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T1 - The respiratory drive to thoracic motoneurones in the cat and its relation to the connections from expiratory bulbospinal neurones
AU - Saywell, S A
AU - Anissimova, N P
AU - Ford, T W
AU - Meehan, Claire Francesca
AU - Kirkwood, P A
PY - 2007
Y1 - 2007
N2 - The descending control of respiratory-related motoneurones in the thoracic spinal cord remains the subject of some debate. In this study, direct connections from expiratory bulbospinal neurones to identified motoneurones were investigated using spike-triggered averaging and the strengths of connection revealed were related to the presence and size of central respiratory drive potentials in the same motoneurones. Intracellular recordings were made from motoneurones in segments T5-T9 of the spinal cord of anaesthetized cats. Spike-triggered averaging from expiratory bulbospinal neurones in the caudal medulla revealed monosynaptic EPSPs in all groups of motoneurones, with the strongest connections to expiratory motoneurones with axons in the internal intercostal nerve. In the latter, connection strength was similar irrespective of the target muscle (e.g. external abdominal oblique or internal intercostal) and the EPSP amplitude was positively correlated with the amplitude of the central respiratory drive potential of the motoneurone. For this group, EPSPs were found in 45/83 bulbospinal neurone/motoneurone pairs, with a mean amplitude of 40.5 microV. The overall strength of the connection supports previous measurements made by cross-correlation, but is about 10 times stronger than that reported in the only previous similar survey to use spike-triggered averaging. Calculations are presented to suggest that this input alone is sufficient to account for all the expiratory depolarization seen in the recorded motoneurones. However, extra sources of input, or amplification of this one, are likely to be necessary to produce a useful motoneurone output.
AB - The descending control of respiratory-related motoneurones in the thoracic spinal cord remains the subject of some debate. In this study, direct connections from expiratory bulbospinal neurones to identified motoneurones were investigated using spike-triggered averaging and the strengths of connection revealed were related to the presence and size of central respiratory drive potentials in the same motoneurones. Intracellular recordings were made from motoneurones in segments T5-T9 of the spinal cord of anaesthetized cats. Spike-triggered averaging from expiratory bulbospinal neurones in the caudal medulla revealed monosynaptic EPSPs in all groups of motoneurones, with the strongest connections to expiratory motoneurones with axons in the internal intercostal nerve. In the latter, connection strength was similar irrespective of the target muscle (e.g. external abdominal oblique or internal intercostal) and the EPSP amplitude was positively correlated with the amplitude of the central respiratory drive potential of the motoneurone. For this group, EPSPs were found in 45/83 bulbospinal neurone/motoneurone pairs, with a mean amplitude of 40.5 microV. The overall strength of the connection supports previous measurements made by cross-correlation, but is about 10 times stronger than that reported in the only previous similar survey to use spike-triggered averaging. Calculations are presented to suggest that this input alone is sufficient to account for all the expiratory depolarization seen in the recorded motoneurones. However, extra sources of input, or amplification of this one, are likely to be necessary to produce a useful motoneurone output.
KW - Action Potentials
KW - Animals
KW - Cats
KW - Efferent Pathways
KW - Electrophysiology
KW - Excitatory Postsynaptic Potentials
KW - Exhalation
KW - Female
KW - Inhalation
KW - Intercostal Nerves
KW - Male
KW - Motor Neurons
KW - Respiratory Center
U2 - 10.1113/jphysiol.2006.122481
DO - 10.1113/jphysiol.2006.122481
M3 - Journal article
C2 - 17204500
VL - 579
SP - 765
EP - 782
JO - The Journal of Physiology
JF - The Journal of Physiology
SN - 0022-3751
IS - Pt 3
ER -
ID: 40314888