TY - JOUR
T1 - Central chemical regulation of breathing movements in fetal lambs
AU - Hohimer, A. Roger
AU - Bissonnette, John M.
AU - Richardson, Bryan S.
AU - Machida, Cindy M.
PY - 1983/4
Y1 - 1983/4
N2 - In 12 chronically prepared fetal lambs between 126 and 136 days of gestation, 17 ventriculocisternal perfusions (123 μl/min) were performed. The concentration of bicarbonate ([HCO3-1]) in the mock cerebrospinal fluid (CSF) perfusate was altered to manipulate the [HCO3-1] in the cerebral ventricles. These perfusions did not systematically alter fetal arterial PCO2, PO2, pH, heart rate or mean blood pressure. Fetal breathing movements (FBM) were noted as rhythmic negative intrathoracic pressures with reference to amniotic fluid pressure. The incidence of FBM was determined and expressed as the percent of the 3 h observation period during which breathing movements were present. Perfusions with mock CSF having an approximately normal [HCO3-1], resulted in cisternal [HCO3-1] of 23.9 ± 0.8 (SEM) meq/L and an incidence of fetal breathing movements (FBM) of 22.1 ± 10.0%. Perfusions with an elevated [HCO3-1] in the mock CSF increased the cisternal [HCO3-1] to 30.7 ± 0.4 meq/L and lowered the incidence of FBM to 0.6 ± 0.2%. Perfusions with a lowered [HCO3-1] mock CSF decreased the cisternal [HCO3-1] to 17.3 ± 0.8 meq/L and increased the incidence of FBM to 45.7 ± 6.8%. These perfusions did not alter the relative incidence of low voltage (LV) versus high voltage (HV) electrocortical (ECOG) state. In 4 animals, low [HCO3-1] perfusions induced FBM in the normally apneic HV ECOG state. We conclude that in the near-term fetal lamb, central chemoreceptors can modulate the incidence of rhythmic respiratory efforts, that tonic afferent stimuli arising from these receptors are critical for the generation of spontaneous FBMs and that central acidosis is capable of evoking FBMs in the normally apneic HV ECOG state.
AB - In 12 chronically prepared fetal lambs between 126 and 136 days of gestation, 17 ventriculocisternal perfusions (123 μl/min) were performed. The concentration of bicarbonate ([HCO3-1]) in the mock cerebrospinal fluid (CSF) perfusate was altered to manipulate the [HCO3-1] in the cerebral ventricles. These perfusions did not systematically alter fetal arterial PCO2, PO2, pH, heart rate or mean blood pressure. Fetal breathing movements (FBM) were noted as rhythmic negative intrathoracic pressures with reference to amniotic fluid pressure. The incidence of FBM was determined and expressed as the percent of the 3 h observation period during which breathing movements were present. Perfusions with mock CSF having an approximately normal [HCO3-1], resulted in cisternal [HCO3-1] of 23.9 ± 0.8 (SEM) meq/L and an incidence of fetal breathing movements (FBM) of 22.1 ± 10.0%. Perfusions with an elevated [HCO3-1] in the mock CSF increased the cisternal [HCO3-1] to 30.7 ± 0.4 meq/L and lowered the incidence of FBM to 0.6 ± 0.2%. Perfusions with a lowered [HCO3-1] mock CSF decreased the cisternal [HCO3-1] to 17.3 ± 0.8 meq/L and increased the incidence of FBM to 45.7 ± 6.8%. These perfusions did not alter the relative incidence of low voltage (LV) versus high voltage (HV) electrocortical (ECOG) state. In 4 animals, low [HCO3-1] perfusions induced FBM in the normally apneic HV ECOG state. We conclude that in the near-term fetal lamb, central chemoreceptors can modulate the incidence of rhythmic respiratory efforts, that tonic afferent stimuli arising from these receptors are critical for the generation of spontaneous FBMs and that central acidosis is capable of evoking FBMs in the normally apneic HV ECOG state.
KW - Apnea
KW - Central chemoreceptors
KW - Cerebrospinal fluid
KW - Control of respiration
KW - Fetal breathing
KW - Sleep state
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U2 - 10.1016/0034-5687(83)90139-1
DO - 10.1016/0034-5687(83)90139-1
M3 - Article
C2 - 6306748
AN - SCOPUS:0020536139
VL - 52
SP - 99
EP - 111
JO - Respiratory Physiology and Neurobiology
JF - Respiratory Physiology and Neurobiology
SN - 1569-9048
IS - 1
ER -