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Are pacemaker neurons active in eupnea when generated by an intact ponto‐medullary network?
Author(s) -
Paton Julian F.R.,
St.John Walter M
Publication year - 2006
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.20.4.a369
Subject(s) - bursting , excitatory postsynaptic potential , neuroscience , inhibitory postsynaptic potential , neurotransmission , blockade , electrophysiology , medicine , anesthesia , biology , receptor
How respiratory rhythmic activity generated by isolated in vitro preparations relates to eupnea recorded either in vivo or in situ , remains controversial. Some believe that the in vitro respiratory activity is generated by pacemaker neurones in the Pre‐Botzinger complex (PBC) that are dependent on a persistent sodium conductance. However, evidence for pacemaker neurones is based entirely on in vitro evidence; they have never been recorded in vivo . In a neonatal (P6–P10) in situ ponto‐medullary preparation generating eupnea, we made patch clamp recordings from the PBC before and after synaptic blockade of fast excitatory and inhibitory transmission. Following synaptic blockade, most neuronal activities ceased or discharged tonically. However some, having either inspiratory or expiratory‐inspiratory discharge patterns in eupnea, exhibited spontaneous rhythmic bursting. These pacemaker neurones displayed: (i) depolarizing ramp‐like membrane potentials in expiration; (ii) periodic discharges not synchronized with the phrenic burst during establishment of synaptic blockade; (iii) a voltage‐dependency in rhythmic bursting frequency following synaptic blockade; (iv) an elimination of rhythmic discharge by riluzole, a blocker of persistent sodium current. We conclude that we have recorded from pacemaker neurons during eupnea. Their rhythmic activity is defined by excitatory and inhibitory synaptic inputs in eupnea. Since riluzole blocks gasping, but not eupnea, these Pre‐Botzinger pacemaker neurons are consistent with a role in the neurogenesis of gasping. NIH, Wellcome Trust & BHF funded research.