Central respiratory activity of the tadpole in vitro brain stem is modulated diversely by nitric oxide.
Nitric oxide (NO) is a potent central neuromodulator of respiration, yet its scope and site of action are unclear. We used 7-nitroindazole (7-NI), a selective inhibitor of endogenous neuronal NO synthesis, to investigate the neurogenesis of respiration in larval bullfrog (Rana catesbeiana) isolated brain stems. 7-NI treatment (0.0625-0.75 mM) increased the specific frequency of buccal ventilation (BV) events, indicating influence on BV central rhythm generators (CRGs). The drug reduced occurrence, altered burst shape, and disrupted clustering of lung ventilation (LV) events, without altering their specific frequency. LV burst occurrence and clustering also differed between pH conditions. We conclude that NO has diverse effects on respiratory rhythmogenesis, being necessary for the expression of respiratory rhythms, inhibiting the frequency of BV CRG, and affecting both shape and clustering of LV bursts through conditional modulation of LV CRG. We confirm central chemosensitivity in these preparations and demonstrate chemomodulation of LV burst clustering and occurrence but not specific frequency. Results support distinct oscillators underlying LV and BV CRGs.
Department of Physiology, Dartmouth Hitchcock Medical Center, Dartmouth College, Lebanon, New Hampshire 03756, USA. michael.b.harris@dartmouth.edu
Michael B
MB
Harris
Richard J A
RJ
Wilson
Konstantinon
K
Vasilakos
Barbara E
BE
Taylor
John E
JE
Remmers
D000704:Analysis of Variance; D000818:Animals; D001933:Brain Stem / Q000187:drug effects / Q000502:physiology*; D002245:Carbon Dioxide / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007191:Indazoles / Q000494:pharmacology; D007814:Larva; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D052248:Nitric Oxide Synthase Type I; D010507:Periodicity; D011892:Rana catesbeiana; D012143:Respiratory Physiological Phenomena / Q000187:drug effects
D004791:Enzyme Inhibitors; D007191:Indazoles; D002245:Carbon Dioxide; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C080122:7-nitroindazole