| Autor: |
Moore, Constance T., Wilson, Christopher G., Mayer, Catherine A., Acquah, Sandra S., Massari, V. John, Haxhiu, Musa A. |
| Předmět: |
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| Zdroj: |
Journal of Applied Physiology; Jan2004, Vol. 96 Issue 1, p260-270, 11p, 4 Black and White Photographs, 2 Diagrams, 6 Graphs |
| Abstrakt: |
GABA is the main inhibitory neurotransmitter that participates in the regulation of cholinergic outflow to the airways. We have tested the hypothesis that a monosynaptic GABAergic circuit modulates the output of airway-related vagal preganglionic neurons (AVPNs) in the rostral nucleus ambiguous by using a dual-labeling electron microscopic method combining immunocytochemistry for glutamic acid decarboxylase (GAD) with retrograde tracing from the trachea. We also determined the effects of blockade of GABA[sub A] receptors on airway smooth muscle tone. The results showed that retrogradely labeled AVPNs received a significant GAD-immunoreactive (GAD-IR) terminal input. Out of a pooled total of 3,161 synaptic contacts with retrogradely labeled somatic and dendritic profiles, 20.2% were GAD-IR. GAD-IR terminals formed significantly more axosomatic synapses than axodendritic synapses (P < 0.02). A dense population of GABAergic synaptic contacts on AVPNs provides a morphological basis for potent physiological effects of GABA on the excitability of AVPNs. GAD-IR terminals formed exclusively symmetric synaptic specializations. GAD-IR terminals were significantly larger (P < 0.05) in both length and width than unlabeled terminals synapsing on AVPNs. Therefore, the structural characteristics of certain nerve terminals may be closely correlated with their function. Pharmacological blockade of GABA[sub A] receptors within the rostral nucleus ambiguous increased activity of putative AVPNs and airway smooth muscle tone. We conclude that a tonically active monosynaptic GABAergic circuit utilizing symmetric synapses regulates the discharge of AVPNs. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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