N-methyl-D-aspartate mechanisms in depolarization of augmenting expiratory neurons during the expulsive phase of fictive cough in decerebrate cats.
Cough reflex is characterized by a large expulsive phase for expelling the mucus or particles from the airway. The present study investigated the involvement of N-methyl-D-aspartate (NMDA) mechanisms in the expulsive phase of cough reflex using decerebrate and paralyzed cats. A fictive cough was induced by repetitive stimulation of the superior laryngeal nerve, which was characterized by an increased inspiratory discharge in the phrenic nerve (the stage 1 of fictive cough; SC1) and large spindle-shaped discharge in the iliohypogastric nerve (the stage 2 of fictive cough; SC2). Intravenous injection of an antagonist of NMDA receptors, dizocilpine (0.1mg/kg), increased the threshold intensity of stimulation for inducing a fictive cough. The SC2 iliohypogastric response was more vulnerable to dizocilpine than the SC1 phrenic response. Membrane potential of augmenting expiratory (aug-E) neurons was recorded from the caudal ventral respiratory group. Aug-E neurons showed a large depolarization with a high frequency discharge during the SC2 in major cases (n=35) and hyperpolarization in minor cases (n=6). Dizocilpine inhibited the occurrence of these SC2 responses of aug-E neurons without any effect on the basal respiratory fluctuations of membrane potential. This drug had no significant effect on waves of excitatory and inhibitory postsynaptic potentials evoked in aug-E neurons by single pulse stimulation of the SLN. The present results demonstrated that NMDA mechanisms contribute preferentially to the expulsive phase response in aug-E neurons during fictive cough reflex.
Haji
Akira
A
Laboratory of Neuropharmacology, School of Pharmacy, Aichi Gakuin University, 1-100 Kusumoto, Chikusa, Nagoya 464-8650, Japan. haji@dpc.aichi-gakuin.ac.jp
Ohi
Yoshiaki
Y
Tsunekawa
Saori
S
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002415:Cats; D003371:Cough / Q000209:etiology / Q000473:pathology*; D003655:Decerebrate State; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004558:Electric Stimulation / Q000009:adverse effects; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D045853:Exhalation / Q000187:drug effects / Q000502:physiology*; D005260:Female; D008297:Male; D016202:N-Methylaspartate / Q000378:metabolism* / Q000494:pharmacology; D009474:Neurons / Q000145:classification / Q000187:drug effects / Q000502:physiology*; D010525:Peripheral Nerves / Q000502:physiology / Q000528:radiation effects; D011930:Reaction Time / Q000187:drug effects / Q000528:radiation effects; D012119:Respiration; D012125:Respiratory Center / Q000166:cytology*
D018691:Excitatory Amino Acid Antagonists; D016202:N-Methylaspartate; D016291:Dizocilpine Maleate