Airway vagal hypertonia is closely related to the severity of
asthma; however, the mechanisms of its genesis are unclear. This study aims to prove that asthmatic airway vagal hypertonia involves neuronal Cl- dyshomeostasis. The experimental airway
allergy model was prepared with
ovalbumin in male adult Sprague-Dawley rats. Plethysmography was used to evaluate airway vagal response to intracisternally injected γ-
aminobutyric acid (
GABA). Immunofluorescent staining and Western-blot assay were used to examine the expression of microglia-specific
proteins, Na+-K+-2Cl-
co-transporter 1 (NKCC1),
K+-Cl- co-transporter 2 (KCC2) and brain-derived
nerve growth factor (
BDNF) in airway vagal centers. Pulmonary inflammatory changes were examined with
hematoxylin and
eosin staining of lung sections and ELISA assay of
ovalbumin-specific
IgE in bronchoalveolar lavage fluid (BALF). The results showed that histochemically, experimental airway
allergy activated microglia, upregulated NKCC1, downregulated KCC2, and increased the content of
BDNF in airway vagal centers. Functionally, experimental airway
allergy augmented the excitatory airway vagal response to intracisternally injected
GABA, which was attenuated by intracisternally pre-injected NKCC1 inhibitor
bumetanide. All of the changes induced by experimental airway
allergy were prevented or mitigated by chronic intracerebroventricular or
intraperitoneal injection of
minocycline, an inhibitor of microglia activation. These results demonstrate that experimental airway
allergy augments the excitatory response of airway vagal centers to
GABA, which might be the result of neuronal Cl- dyshomeostasis subsequent to microglia activation, increased
BDNF release and altered expression of Cl- transporters. Cl- dyshomeostasis in airway vagal centers might contribute to the genesis of airway vagal hypertonia in
asthma.