title: Inspiration-promoting vagal reflex in anaesthetized rabbits after rostral dorsolateral pons lesions.
abstract: The centrally generated respiratory rhythm is under strong modulation by peripheral information, such as that from the slowly adapting pulmonary stretch receptors (SA-PSRs) conveyed via the vagus nerve. We have already demonstrated that vagal afferent stimulation at a low frequency (5-40 Hz), or holding the lung volume at the end-expiratory level (no-inflation test) prevents spontaneous termination of the inspiratory (I) phase or initiates I activity in anaesthetized rabbits in which the NMDA receptors (NMDA-Rs) are pharmacologically blocked. Here we show that this I-promoting vagal reflex also becomes manifest in animals where the pontine respiratory groups are ablated. Following lesions of the rostral dorsolateral pons, including the nucleus parabrachialis medialis and Kölliker-Fuse nucleus, with radio-frequency current or local injection of kainic acid, low-frequency stimulation of the vagus nerve and the no-inflation test significantly prolonged the I phase in a manner highly similar to that observed in rabbits with NMDA-R block. Brief stimuli at low frequency during the mid-expiratory (E) phase evoked I discharge with a latency significantly smaller and less variable than that before the lesions. It is concluded that low-frequency input from the SA-PSR suppresses I-to-E phase transition and promotes central I activity when the medullary respiratory network is released from pontine influence, which involves NMDA-R-mediated signalling.
authors.affiliation: Department of Pharmacology II, Jikei University School of Medicine, Tokyo, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Takano
authors.forename: Fusao
authors.initials: F
authors.lastname: Kato
mesh_terms: D000758:Anesthesia; D000818:Animals; D004558:Electric Stimulation; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D007608:Kainic Acid / Q000633:toxicity; D008168:Lung / Q000502:physiology; D008297:Male; D008845:Microinjections; D010791:Phrenic Nerve / Q000502:physiology; D011149:Pons / Q000502:physiology*; D011661:Pulmonary Stretch Receptors; D011817:Rabbits; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D012018:Reflex / Q000502:physiology*; D015656:Respiratory Mechanics / Q000502:physiology*; D014630:Vagus Nerve / Q000502:physiology*
chemical_list: D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D007608:Kainic Acid