title: [Effect of microsectioning medulla, pH and temperature on rhythmical respiratory discharge activity of medulla-spinal preparation isolated from newborn rat].
abstract: OBJECTIVE
  The brain stem and the spinal cord were isolated from 0-4-day-old rats, placed in a bath and perfused with artificial cerebrospinal fluid (aCSF) in vitro. Spontaneous rhythmic neural activity could be recorded from phrenic (C4v, C5v) and hypoglossal nerves (XII). By microsection of medulla of medulla-spinal preparation, rhythmical respiratory discharge activity (RRDA) of C4v, C5v and XII were observed.
  
  
  RESULTS
  Medulla-spinal preparation survival about six to eight hours when preparation was perfused continuously with aCSF. RRDA of C4v or C5v and XII was synchronous and continued about four to six hours. RRDA of C4v or C5v and XII could not be perturbed until a level of 500 microm rostral to obex was reached when cutting brain stem coronally in a rostral-to-caudal direction, and until a horizontal plane at middle level was reached when cutting brain stem dorsal-ventrally from dorsal surface of the stem. RRDA of XII also could not be perturbed until a level just caudal to the caudalis root of the XII (50 micro m caudal to the obex) when cutting brain stem caudal-rostrally. Frequency of respiration gradually decreased and amplitude of RRDA gradully enhanced when pH of fluid perfused from 7.45 up to 7.85, and RRDA enhanced when from 7.35 down to 6.85 and ceased when 4.5 RRDA enhanced when temperature of fluid perfused from 27 degrees C up to 37 degrees C, and decreased when from 38 degrees C up to 41 degrees C and when from 27 degrees C down to 23 degrees C, and ceased when 42 degrees C or 22 degrees C.
  
  
  CONCLUSIONS
  A respiratory rhythm generating site is located in mNRF, there are neurons those are susceptible to change of pH and temperature in mNRF.
authors.affiliation: Department of Physiology, First Military Medical University, Guangzhou 510515.
authors.forename: D H
authors.initials: DH
authors.lastname: Hu
authors.forename: Z H
authors.initials: ZH
authors.lastname: Wu
authors.forename: Y
authors.initials: Y
authors.lastname: Gao
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D006863:Hydrogen-Ion Concentration; D007002:Hypoglossal Nerve / Q000502:physiology; D066298:In Vitro Techniques; D008526:Medulla Oblongata / Q000293:injuries / Q000502:physiology*; D010507:Periodicity; D010791:Phrenic Nerve / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000502:physiology*; D013696:Temperature