The cerebellar fastigial nucleus contributes to CO2-H+ ventilatory sensitivity in awake goats.
The purpose of this study was to test the hypothesis that an intact cerebellar fastigial nucleus (CFN) is an important determinant of CO(2)-H(+) sensitivity during wakefulness. Bilateral, stainless steel microtubules were implanted into the CFN (N=9) for injection (0.5-10 microl) of the neurotoxin ibotenic acid. Two or more weeks after implantation of the microtubules, eupneic breathing and CO(2)-H(+) sensitivity did not differ significantly (P>0.10) from pre-implantation conditions. Injection of ibotenic acid (50 mM) did not significantly alter eupneic Pa(CO2) (P>0.10). The coefficient of variation of eupneic Pa(CO2) was 4.0+/-0.6 and 3.7+/-0.4% over the 2 weeks before and after the lesion, respectively. CO(2)-H(+) sensitivity expressed as inspired ventilation/Pa(CO2) decreased from 2.15+/-0.17 pre-lesion to 1.58+/-0.26 l/(min mmHg) 3-6 days post-lesion (P<0.02, -27%). There was no significant (P>0.10) recovery of sensitivity between 7 and 10 days post-lesion. The lesion also increased (P<0.05) the day-to-day variability of this index by nearly 100%. When CO(2) sensitivity was expressed as elevated inspired CO(2)/room air V (I), values at 7%, but not 3 and 5% inspired CO(2), were reduced and more variable (P<0.05) after the ibotenic acid injections. We conclude that during wakefulness, the CFN contributes relatively more to overall ventilatory drive at high relative to low levels of hypercapnia.
Martino
P F
PF
Department of Physiology, Medical College of Wisconsin, Milwaukee, WI 53226, USA. paul.martino@wright.edu
Davis
S
S
Opansky
C
C
Krause
K
K
Bonis
J M
JM
Pan
L G
LG
Qian
B
B
Forster
H V
HV
D000704:Analysis of Variance; D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D002245:Carbon Dioxide / Q000032:analysis; D002529:Cerebellar Nuclei / Q000187:drug effects / Q000502:physiology*; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D005260:Female; D006041:Goats / Q000033:anatomy & histology / Q000502:physiology*; D006859:Hydrogen / Q000032:analysis; D007051:Ibotenic Acid / Q000494:pharmacology; D008297:Male; D011659:Pulmonary Gas Exchange / Q000187:drug effects / Q000502:physiology; D015656:Respiratory Mechanics / Q000187:drug effects / Q000502:physiology*; D014851:Wakefulness / Q000502:physiology*
D018690:Excitatory Amino Acid Agonists; D002245:Carbon Dioxide; D007051:Ibotenic Acid; D006859:Hydrogen