title: Participation of the dorsal periaqueductal grey matter in the hypoxic ventilatory response in unanaesthetized rats.
abstract: OBJECTIVE
  Although periaqueductal grey matter activation is known to elicit respiratory and cardiovascular responses, the role of this midbrain area in the compensatory responses to hypoxia is still unknown. To test the participation of the periaqueductal grey matter in cardiorespiratory and thermal responses to hypoxia in adult male Wistar rats, we performed a chemical lesion of the dorsolateral/dorsomedial or the ventrolateral/lateral periaqueductal grey matter using ibotenic acid.
  
  
  METHODS
  Pulmonary ventilation, mean arterial pressure, heart rate and body temperature were measured in unanaesthetized rats during normoxic and hypoxic exposure (5, 15, 30 min, 7% O2).
  
  
  RESULTS
  An ibotenic acid lesion of the dorsolateral/dorsomedial periaqueductal grey matter caused a higher increase in pulmonary ventilation (67.1%, 1730±282.5 mL kg(-1) min(-1)) compared to the Sham group (991.4±194 mL kg(-1) min(-1)) after 15 min in hypoxia, whereas for the ventrolateral/Lateral periaqueductal grey matter lesion, no differences were observed between groups. Mean arterial pressure, heart rate and body temperature were not affected by a dorsolateral/dorsomedial or ventrolateral/lateral periaqueductal grey matter lesion.
  
  
  CONCLUSIONS
  Middle to caudal portions of the dorsolateral/dorsomedial periaqueductal grey matter neurones modulate the hypoxic ventilatory response, exerting an inhibitory modulation during low O2 situations. In addition, the middle to caudal portions of the dorsolateral/dorsomedial or ventrolateral/lateral periaqueductal grey matter do not appear to exert a tonic role on cardiovascular or thermal parameters during normoxic and hypoxic conditions.
authors.affiliation: Department of Animal Morphology and Physiology, São Paulo State University (FCAV/UNESP), Jaboticabal, SP, Brazil.
authors.forename: L T
authors.initials: LT
authors.lastname: Lopes
authors.forename: V
authors.initials: V
authors.lastname: Biancardi
authors.forename: E B
authors.initials: EB
authors.lastname: Vieira
authors.forename: C
authors.initials: C
authors.lastname: Leite-Panissi
authors.forename: K C
authors.initials: KC
authors.lastname: Bícego
authors.forename: L H
authors.initials: LH
authors.lastname: Gargaglioni
mesh_terms: D000818:Animals; D062186:Arterial Pressure; D001833:Body Temperature Regulation; D002245:Carbon Dioxide / Q000097:blood; D003243:Consciousness; D004195:Disease Models, Animal; D006339:Heart Rate; D000860:Hypoxia / Q000097:blood / Q000503:physiopathology*; D007051:Ibotenic Acid / Q000633:toxicity; D008168:Lung / Q000294:innervation*; D008297:Male; D010100:Oxygen / Q000097:blood; D010487:Periaqueductal Gray / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology*; D012123:Pulmonary Ventilation / Q000187:drug effects; D017208:Rats, Wistar; D012018:Reflex; D013997:Time Factors
chemical_list: D002245:Carbon Dioxide; D007051:Ibotenic Acid; D010100:Oxygen
keywords: midbrain; peripheral chemoreflex; respiration