Neurones in a discrete region of the nucleus tractus solitarius are required for the Breuer-Hering reflex in rat.
AUTOR(ES)
Bonham, A C
RESUMO
1. The Breuer-Hering reflex consists of a shortening of inspiration and lengthening of expiration in response to afferent input from slowly adapting pulmonary stretch receptors (SAR). We hypothesized that neurones in a discrete region of the nucleus tractus solitarius (NTS) are required for producing the reflex. Accordingly, the present studies were undertaken to: (1) identify sites in the NTS in which chemical excitation of neurones inhibited phrenic nerve discharge in a manner consistent with SAR activation, (2) determine whether localized interruption of synaptic transmission prevented the Breuer-Hering reflex, and (3) determine whether these regions contained pump cells and SAR terminal afferents. Studies were carried out in urethane-anaesthetized rats. 2. Injection of picomoles of an excitatory amino acid, DL-homocysteic acid (DLH), in the NTS, at the rostrocaudal level of the area postrema and immediately medial to the tractus solitarius, silenced phrenic nerve activity similarly to that expected from SAR activation. These apnoeas lasted from 3 to 43 s and were produced with little or no change in arterial pressure or heart rate. 3. The Breuer-Hering reflex, physiologically activated by maintaining lung inflation, was transiently impaired by interruption of synaptic transmission following injections of cobalt chloride in the DLH-responsive region. 4. Pump cell (SAR interneurone) and SAR afferent activity were recorded at the site in which DLH produced apnoea. 5. Taken together, the results of chemical excitation, interruption of synaptic transmission and extracellular recording, suggest that cells within a discrete region of the NTS, probably pump cells, are necessary for the production of the Breuer-Hering reflex.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1189930Documentos Relacionados
- Neurones in commissural nucleus tractus solitarii required for full expression of the pulmonary C fibre reflex in rat.
- Reversible abnormalities of the Hering Breuer reflex in acrylamide neuropathy.
- A gamma-aminobutyric-acid-mediated inhibition of neurones in the nucleus tractus solitarius of the cat.
- Hypothalamic inhibition of neurones in the nucleus tractus solitarius of the cat is GABA mediated.
- Monosynaptic excitation of thoracic motoneurones by inspiratory neurones of the nucleus tractus solitarius in the cat.