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Electrophysiological properties of abdominal muscle‐projecting expiratory motoneurons of rats
Author(s) -
Silva Melina P.,
Moraes Davi J.A.,
Bonagamba Leni G.H.,
Varanda Wamberto A.,
Machado Benedito H.
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.1295.4
Subject(s) - electrophysiology , chemistry , neuroscience , resting potential , spinal cord , membrane potential , anesthesia , anatomy , medicine , biology
Expiration is considered a passive process during resting breathing condition. There is a lack of information about the intrinsic electrophysiological properties of expiratory motoneurons and their possible changes in conditions in which the expiration becomes an active process, such as hypoxia. Considering that abdominal expiratory muscle activity depends on excitability of these motoneurons, here we aimed to characterize the electrophysiological properties of abdominal muscle‐projecting expiratory motoneurons combining retrograde tracer, immunofluorescence and whole cell patch clamp, in thoraco‐lumbar spinal cord slices from juvenile Wistar rats. Three different types of cholinergic expiratory motoneurons with similar capacitance were recorded: neurons with spontaneous action potentials whose resting potential hyperpolarizes (−65 ± 5 mV vs −69.7 ± 4 mV, n=9) and firing frequency decreases (8.5 ± 2 Hz vs 1.7 ± 1.3 Hz, n=9) after synaptic blockade. The passive properties of these motoneurons, such as input resistance and excitability, did not change after synaptic blockade (Ri = 0.16 ± 0.03 GΩ vs 0.13 ± 0.03 GΩ; Excitability = 40 ± 10 Hz vs 32 ± 11 Hz, n=9). The second group of motoneurons also exhibited spontaneous action potentials, but showed spike frequency adaptation, slowing or ceasing firing frequency during a maintained stimulus. Their membrane potential also hyperpolarized (−60 ± 1 mV vs −66 ± 1 mV, n=4) and firing frequency was abolished by synaptic blockade. On the other hand, no differences in the input resistance was observed (0.13 ± 0.01 GΩ vs 0.11 ± 0.01 GΩ, n=4). The third group did not show spontaneous action potential and synaptic blockade did not change membrane potential (−72.2 ± 2 mV vs −76 ± 3 mV, n=6) or input resistance (0.1 ± 0.04 GΩ vs 0.06 ± 0.02 GΩ, n=6). However, synaptic blockade decreased their intrinsic excitability. Overall, our data show that there are three different populations of abdominal muscle‐projecting expiratory motoneurons in rats, which may contribute to recruitment of expiratory muscles in different physiological and pathophysiological conditions. Support or Funding Information FAPESP, CAPES, CNPQ