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ENVIRONMENTAL, EXERCISE AND RESPIRATORY PHYSIOLOGY

Medullary lateral tegmental field: control of respiratory rate and vagal lung inflation afferent influences on sympathetic nerve discharge

Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan

Submitted 16 September 2004 ; accepted in final form 12 December 2004

We used spectral analysis and event-triggered averaging to determine the effects of chemical inactivation of the medullary lateral tegmental field (LTF) on 1) the relationship of intratracheal pressure (ITP, an index of vagal lung inflation afferent activity) to sympathetic nerve discharge (SND) and phrenic nerve activity (PNA) and 2) central respiratory rate in paralyzed, artificially ventilated dial-urethane-anesthetized cats. ITP-SND coherence value at the frequency of artificial ventilation was significantly (P < 0.05; n = 18) reduced from 0.73 ± 0.04 (mean ± SE) to 0.24 ± 0.04 after bilateral microinjection of muscimol into the LTF. Central respiratory rate was unexpectedly increased in 12 of these experiments (0.28 ± 0.03 vs. 0.95 ± 0.25 Hz). The ITP-PNA coherence value was variably affected by chemical inactivation of the LTF. It was unchanged when central respiratory rate was also not altered, decreased when respiratory rate was increased above the rate of artificial ventilation, and increased when respiratory rate was raised from a value below the rate of artificial ventilation to the same frequency as the ventilator. Chemical inactivation of the LTF increased central respiratory rate in four of six vagotomized cats but did not significantly affect the PNA-SND coherence value. These data demonstrate that the LTF 1) plays a critical role in mediating the effects of vagal lung inflation afferents on SND but not PNA, 2) helps maintain central respiratory rate in the physiological range, but 3) is not involved in the coupling of central respiratory and sympathetic circuits.

cardiorespiratory synchronization; dorsal respiratory group; Hering-Breuer reflex; phrenic nerve activity; respiratory-related rhythm; ventral respiratory group

This article has been cited by other articles:

				H. S. Orer, G. L. Gebber, and S. M. Barman Medullary lateral tegmental field neurons influence the timing and pattern of phrenic nerve activity in cats J Appl Physiol, August 1, 2006; 101(2): 521 - 530. [Abstract] [Full Text] [PDF]

				S. M. Barman, S. W. Phillips, and G. L. Gebber Medullary lateral tegmental field mediates the cardiovascular but not respiratory component of the Bezold-Jarisch reflex in the cat Am J Physiol Regulatory Integrative Comp Physiol, December 1, 2005; 289(6): R1693 - R1702. [Abstract] [Full Text] [PDF]