Submitted on March 18, 2006
Accepted on May 26, 2006
Lesions in the Cerebellar Fastigial Nucleus Have a Small Effect on the Hyperpnea Needed to Meet the Gas Exchange Requirements of Submaximal Exercise
Paul Frank Martino1*, Suzanne Davis1, Cynthia Opansky2, Katie Krause2, Joshua M Bonis2, Stephen G Czerniak2, Lawrence G Pan3, Baogong Qian4, and Hubert V. Forster5
1 Physiology, The Medical College of Wisconsin, Milwaukee, Wisconsin, United States
2 Physiology, The Medical College of Wisconsin, Milwaukee, Wisconsin, United States; Milwaukee, Wisconsin, United States
3 Physiology, The Medical College of Wisconsin, Milwaukee, Wisconsin, United States; Physical Therapy, Marquette University, Milwaukee, Wisconsin, United States
4 Milwaukee, Wisconsin, United States; Physiology, The Medical College of Wisconsin, Milwaukee, Wisconsin, United States
5 Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States; Zablocki V.A. Medical Center, Milwaukee, Wisconsin, United States
* To whom correspondence should be addressed. E-mail: pmartino{at}mcw.edu.
The purpose of this study was to test the hypothesis that an intact cerebellar fastigial nucleus (CFN) is necessary for the hyperpnea of submaximal exercise. Bilateral stainless steel microtubules (MT) (cannula) were implanted inside (n = 12) or outside (n = 2) the CFN for injection (0.5 to 10 ul) of the neurotoxin ibotenic acid. All goats had difficulty maintaining posture and walking for up to one month after the implantation of the microtubules and again for hours or days after injecting the neurotoxin. Post mortem histology indicated there were 55% fewer living neurons (Table 1A, P < .001, n = 9, 3720 ± 553 vs.1670 ± 192) in the CFN of the experimental goats compared to a control group of goats. As is typical for goats (12, 33), prior to implantation of the microtubules, the decrease in PaCO 2 from rest during mild and moderate treadmill exercise was 2.0 ± 0.39 and 3.5 ± 0.45 mmHg, respectively. Implantation of the microtubules did not significantly change this exercise hyperventilation. However, neurotoxic with 10 ul ibotenic acid lesions significantly (P < .05) attenuated the decrease in PaCO2 by 1.3 and 2.8 mmHg at the first and second workloads respectively. Injections of methysergide, serotonin receptor antagonist slightly attenuated the decrease in PaCO2 at the higher workload. The attenuation of the exercise hypocapnia at both workloads in CFN lesioned goats suggests that the CFN is part of the system that enables the ventilatory response to meet the gas exchange requirements of submaximal exercise.
