Opioid-induced quantal slowing reveals dual networks for respiratory rhythm generation.
Current consensus holds that a single medullary network generates respiratory rhythm in mammals. Pre-Bötzinger Complex inspiratory (I) neurons, isolated in transverse slices, and preinspiratory (pre-I) neurons, found only in more intact en bloc preparations and in vivo, are each proposed as necessary for rhythm generation. Opioids slow I, but not pre-I, neuronal burst periods. In slices, opioids gradually lengthened respiratory periods, whereas in more intact preparations, periods jumped nondeterministically to integer multiples of the control period (quantal slowing). These findings suggest that opioid-induced quantal slowing results from transmission failure of rhythmic drive from pre-I neurons to preBötC I networks, depressed below threshold for spontaneous rhythmic activity. Thus, both I (in the slice), and pre-I neurons are sufficient for respiratory rhythmogenesis.
Mellen
Nicholas M
NM
Department of Neurobiology, University of California, Los Angeles, P.O. Box 951763, Los Angeles, CA 90095, USA. nmellen@ucla.edu
Janczewski
Wiktor A
WA
Bocchiaro
Christopher M
CM
Feldman
Jack L
JL
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D001683:Biological Clocks / Q000187:drug effects / Q000502:physiology; D001933:Brain Stem / Q000187:drug effects / Q000502:physiology; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)- / Q000494:pharmacology; D066298:In Vitro Techniques; D009294:Narcotics / Q000494:pharmacology*; D009415:Nerve Net / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017450:Receptors, Opioid, mu / Q000819:agonists / Q000502:physiology; D012119:Respiration / Q000187:drug effects*
D009294:Narcotics; D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-