Asymmetric control of inspiratory and expiratory phases by excitability in the respiratory network of neonatal mice in vitro.
J Physiol
; 587(Pt 6): 1217-31, 2009 Mar 15.
Article
em En
| MEDLINE
| ID: mdl-19171658
ABSTRACT
Rhythmic motor behaviours consist of alternating movements, e.g. swing-stance in stepping, jaw opening and closing during chewing, and inspiration-expiration in breathing, which must be labile in frequency, and in some cases, in the duration of individual phases, to adjust to physiological demands. These movements are the expression of underlying neural circuits whose organization governs the properties of the motor behaviour. To determine if the ability to operate over a broad range of frequencies in respiration is expressed in the rhythm generator, we isolated the kernel of essential respiratory circuits using rhythmically active in vitro slices from neonatal mice. We show respiratory motor output in these slices at very low frequencies (0.008 Hz), well below the typical frequency in vitro (approximately 0.2 Hz) and in most intact normothermic mammals. Across this broad range of frequencies, inspiratory motor output bursts remained remarkably constant in pattern, i.e. duration, peak amplitude and area. The change in frequency was instead attributable to increased interburst interval, and was largely unaffected by removal of fast inhibitory transmission. Modulation of the frequency was primarily achieved by manipulating extracellular potassium, which significantly affects neuronal excitability. When excitability was lowered to slow down, or in some cases stop, spontaneous rhythm, brief stimulation of the respiratory network with a glutamatergic agonist could evoke (rhythmic) motor output. In slices with slow (<0.02 Hz) spontaneous rhythms, evoked motor output could follow a spontaneous burst at short (
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Centro Respiratório
/
Potenciais de Ação
/
Inalação
/
Expiração
/
Neurônios Motores
Limite:
Animals
Idioma:
En
Revista:
J Physiol
Ano de publicação:
2009
Tipo de documento:
Article
País de afiliação:
Estados Unidos
País de publicação:
ENGLAND
/
ESCOCIA
/
GB
/
GREAT BRITAIN
/
INGLATERRA
/
REINO UNIDO
/
SCOTLAND
/
UK
/
UNITED KINGDOM