Respiration during hypothermia: effect of rewarming intermediate areas of ventral medulla

1985 ◽  
Vol 59 (5) ◽  
pp. 1423-1427 ◽  
Author(s):  
J. P. Kiley ◽  
F. L. Eldridge ◽  
D. E. Millhorn
Keyword(s):  
Phrenic Nerve ◽  
Respiratory Activity ◽  
Ventral Surface ◽  
Respiratory Frequency ◽  
Independent Effect ◽  
Neural Function ◽  
Nerve Activity ◽  
Intermediate Area ◽  
Phrenic Nerve Activity ◽  
Significant Reversal

We studied respiration (phrenic nerve activity) during progressive hypothermia to as low as 30.5 degrees C in five anesthetized, paralyzed, glomectomized, and vagotomized cats. PCO2 was maintained at a constant level throughout the experiments. We confirmed the results of a previous study (J. P. Kiley, F. L. Eldridge, and D. E. Millhorn, J. Appl. Physiol. 58: 295–312, 1985) in which respiratory minute output decreased progressively with cooling and respiratory frequency decreased markedly. In addition we show that focal rewarming to normal temperature (37.5 degrees C) of the structures in the intermediate areas on the ventral surface of the medulla resulted in a significant reversal of the depressed respiratory minute activity observed with hypothermia. Respiratory frequency, however, was unaffected by intermediate area rewarming. We conclude that the decreased respiratory activity during hypothermia is due to a generalized interference with neural function. A major portion of these effects is due to cooling of the intermediate areas, but the slowing of respiratory frequency appears to be an independent effect.

Ventral medullary surface inputs to cervical sympathetic respiratory oscillations

1987 ◽  
Vol 252 (6) ◽  
pp. R1032-R1038 ◽  
Author(s):  
E. Van Lunteren ◽  
J. Mitra ◽  
N. R. Prabhakar ◽  
M. A. Haxhiu ◽  
N. S. Cherniack
Keyword(s):  
Phrenic Nerve ◽  
Sympathetic Activity ◽  
Respiratory Activity ◽  
Related Activity ◽  
Nerve Activity ◽  
Intermediate Area ◽  
Phrenic Nerve Activity ◽  
Cervical Sympathetic ◽  
Ventral Medullary Surface

To examine the effects of focally cooling three areas (rostral, intermediate, and caudal) of the ventral medullary surface (VMS) on respiratory oscillations in cervical sympathetic and phrenic nerve activity, 12 cats were anesthetized, vagotomized, paralyzed, and artificially ventilated with 7% CO2 in O2. Cooling the intermediate area from 37 to 20 degrees C significantly reduced the magnitude of respiratory oscillations in both cervical sympathetic activity (P less than 0.001) and phrenic activity (P less than 0.001). Graded cooling of all three areas caused graded reductions in sympathetic respiratory-related activity that were comparable to the reductions in phrenic activity. The magnitude of the reductions in sympathetic respiratory oscillations was greatest for the intermediate area, followed in order by the caudal and rostral areas. Eight cats also underwent graded VMS cooling while ventilated with 3% CO2 in O2 and 100% O2. At each level of inspired CO2, graded cooling resulted in graded reductions in respiratory oscillations in sympathetic activity; conversely, at each medullary temperature, graded increases in inspired CO2 caused graded increases in cervical sympathetic respiratory activity. These results suggest that all three areas of the VMS influence respiratory oscillations in cervical sympathetic activity, although to different extents.

Rhythmic phrenic nerve activity and respiratory activity in spinal dogs

1977 ◽  
Vol 29 (3) ◽  
pp. 247-254 ◽  
Author(s):  
Caryl J. Coglianese ◽  
C.N. Peiss ◽  
R.D. Wurster
Keyword(s):  
Phrenic Nerve ◽  
Respiratory Activity ◽  
Nerve Activity ◽  
Phrenic Nerve Activity

Patterns of neural and muscular electrical activity in costal and crural portions of the diaphragm

1989 ◽  
Vol 66 (5) ◽  
pp. 2092-2100 ◽  
Author(s):  
L. M. Oyer ◽  
S. L. Knuth ◽  
D. K. Ward ◽  
D. Bartlett
Keyword(s):  
Electrical Activity ◽  
Phrenic Nerve ◽  
Respiratory Activity ◽  
Respiratory Muscles ◽  
Emg Activity ◽  
Neural Responses ◽  
Nerve Activity ◽  
Phrenic Nerve Activity ◽  
Central Respiratory Activity ◽  
Spontaneously Breathing

To determine whether the central respiratory drives to costal and crural portions of the diaphragm differ from each other in response to chemical and mechanical feedbacks, activities of costal and crural branches of the phrenic nerve were recorded in decerebrate paralyzed cats, studied either with vagi intact and servo-ventilated in accordance with their phrenic nerve activity or vagotomized and ventilated conventionally. Costal and crural electromyograms (EMGs) were recorded in decerebrate spontaneously breathing cats. Hypercapnia and hypoxia resulted in significant increases in peak integrated costal, crural, and whole phrenic nerve activities when the vagi were either intact or cut. However, there were no consistent differences between costal and crural neural responses. Left crural EMG activity was increased significantly more than left costal EMG activity in response to hypercapnia and hypoxia. These results indicate that the central neural inputs to costal and crural portions of the diaphragm are similar in eupnea and in response to chemical and mechanical feedback in decerebrate paralyzed cats. The observed differences in EMG activities in spontaneously breathing animals must arise from modulation of central respiratory activity by mechanoreceptor feedback from respiratory muscles, likely the diaphragm itself.

Role of the ventral surface of medulla in the generation of Mayer waves

1989 ◽  
Vol 257 (4) ◽  
pp. R804-R809 ◽  
Author(s):  
M. A. Haxhiu ◽  
E. van Lunteren ◽  
E. C. Deal ◽  
N. S. Cherniack
Keyword(s):  
Blood Pressure ◽  
Arterial Blood Pressure ◽  
Phrenic Nerve ◽  
Pressure Oscillation ◽  
Nerve Activity ◽  
Intermediate Area ◽  
Mayer Waves ◽  
Phrenic Nerve Activity ◽  
Arterial Blood ◽  
Cyclic Changes

The regions adjacent to the ventrolateral medullary surface (VMS) play critical roles in the regulation of respiratory and cardiovascular function. Furthermore, these areas seem to be important sites for the integration of afferent inputs from certain sensory organs and the source of excitatory inputs to preganglionic sympathetic and parasympathetic neurons. To determine whether the VMS contributes to the generation of nonrespiratory-related periodic oscillations of arterial blood pressure (Mayer waves), excitatory substances, such as N-methyl-D-aspartate (NMDA), cholinergic agonists, and neuropeptides (substance P, neurokinin A, neurotensin), were applied topically to the intermediate area of VMS in anesthetized cats. In addition, the effects of application of lidocaine and inhibitory substances (benzodiazepines) on Mayer waves were studied. After application of excitatory substances to the VMS, we observed oscillations of arterial blood pressure, recurring with a period of 17.8 +/- 10 (SE) s, which had similar characteristics as the Mayer waves recorded during hypercapnia or hypoxia. In addition, cyclic changes in phrenic nerve activity and tracheal tone occurred with the same periodicity as arterial blood pressure oscillation. Application of lidocaine or benzodiazepines on the intermediate area of the VMS abolished Mayer waves observed during hypercapnia, hypoxia, or application of excitatory substances. These findings show for the first time that the VMS can be considered as one of several synaptic relays involved in the generation of arterial blood pressure oscillation, as well as the cyclic changes in phrenic nerve activity and tracheal smooth muscle tone that occur simultaneously.

A role for the ventral surface of the medulla in regulation of nasal resistance

1987 ◽  
Vol 253 (3) ◽  
pp. R494-R500 ◽  
Author(s):  
M. A. Haxhiu ◽  
K. P. Strohl ◽  
M. P. Norcia ◽  
E. van Lunteren ◽  
E. C. Deal ◽  
...  
Keyword(s):  
Phrenic Nerve ◽  
Nmda Antagonist ◽  
Ventral Surface ◽  
Nasal Resistance ◽  
Nasal Patency ◽  
Nerve Activity ◽  
Phrenic Nerve Activity ◽  
Cervical Sympathetic ◽  
Ventral Medullary Surface ◽  
Nasal Blood Vessels

Nasal resistance is known to be affected by changes in nasal blood volume and hence to depend on sympathetic discharge to nasal blood vessels. Structures located superficially near the ventrolateral surface of the medulla significantly affect respiratory and sympathetic activity and the tone of the trachea. To assess the importance of these structures on nasal patency, we measured transnasal pressure at a constant flow and examined the change in pressure produced by topically applied N-methyl-D-aspartic acid (NMDA). Experiments were performed in chloralose-anesthetized, paralyzed, and artificially ventilated cats. NMDA administered on the intermediate area of the ventral surface of the medulla decreased transnasal pressure and increased phrenic nerve activity. The response to NMDA could be diminished or abolished by application to the ventral medullary surface of the NMDA antagonist 2-amino-5-phosphonovalerate (2-APV) or the local anesthetic lidocaine. Carotid sinus denervation and posthypothalamic decerebration did not alter the nasal and phrenic nerve responses to NMDA; however, cervical sympathetic denervation decreased these responses, both in intact and in bilaterally adrenalectomized animals. Therefore, activation of NMDA receptors on structures near the ventral surface of the medulla increases tone in the nasal vasculature and leads to a response pattern that includes changes in not only phrenic nerve activity and blood pressure but also nasal patency.

Daily acute intermittent hypoxia enhances phrenic motor output and stimulus-evoked phrenic responses in rats

2021 ◽  
Author(s):  
Raphael Rodrigues Perim ◽  
Michael D. Sunshine ◽  
Joseph F. Welch ◽  
Juliet Santiago ◽  
Ashley Holland ◽  
...  
Keyword(s):  
Motor Neurons ◽  
Phrenic Nerve ◽  
Intermittent Hypoxia ◽  
Neural Control ◽  
Respiratory Cycle ◽  
Evoked Responses ◽  
Nerve Activity ◽  
Synaptic Inputs ◽  
Phrenic Nerve Activity ◽  
The Impact

Plasticity is a hallmark of the respiratory neural control system. Phrenic long-term facilitation (pLTF) is one form of respiratory plasticity characterized by persistent increases in phrenic nerve activity following acute intermittent hypoxia (AIH). Although there is evidence that key steps in the cellular pathway giving rise to pLTF are localized within phrenic motor neurons (PMNs), the impact of AIH on the strength of breathing-related synaptic inputs to PMNs remains unclear. Further, the functional impact of AIH is enhanced by repeated/daily exposure to AIH (dAIH). Here, we explored the effects of AIH vs. 2 weeks of dAIH preconditioning on spontaneous and evoked responses recorded in anesthetized, paralyzed (with pancuronium bromide) and mechanically ventilated rats. Evoked phrenic potentials were elicited by respiratory cycle-triggered lateral funiculus stimulation at C2 delivered prior to- and 60 min post-AIH (or an equivalent time in controls). Charge-balanced biphasic pulses (100 µs/phase) of progressively increasing intensity (100 to 700 µA) were delivered during the inspiratory and expiratory phases of the respiratory cycle. Although robust pLTF (~60% from baseline) was observed after a single exposure to moderate AIH (3 x 5 min; 5 min intervals), there was no effect on evoked phrenic responses, contrary to our initial hypothesis. However, in rats preconditioned with dAIH, baseline phrenic nerve activity and evoked responses were increased, suggesting that repeated exposure to AIH enhances functional synaptic strength when assessed using this technique. The impact of daily AIH preconditioning on synaptic inputs to PMNs raises interesting questions that require further exploration.

Influence of the ventral surface of the medulla on tracheal responses to CO2

1986 ◽  
Vol 61 (3) ◽  
pp. 1091-1097 ◽  
Author(s):  
E. C. Deal ◽  
M. A. Haxhiu ◽  
M. P. Norcia ◽  
J. Mitra ◽  
N. S. Cherniack
Keyword(s):  
Motor Activity ◽  
Phrenic Nerve ◽  
Ventral Surface ◽  
Intermediate Area ◽  
Tracheal Pressure ◽  
Cervical Trachea ◽  
Airway Responses ◽  
Airway Tone ◽  
Pressure Changes ◽  
Nerve Discharge

These studies investigated the role of the intermediate area of the ventral surface of the medulla (VMS) in the tracheal constriction produced by hypercapnia. Experiments were performed in chloralose-anesthetized, paralyzed, and artificially ventilated cats. Airway responses were assessed from pressure changes in a bypassed segment of the rostral cervical trachea. Hyperoxic hypercapnia increased tracheal pressure and phrenic nerve activity. Intravenous atropine pretreatment or vagotomy abolished the changes in tracheal pressure without affecting phrenic nerve discharge. Rapid cooling of the intermediate area reversed the tracheal constriction produced by hypercapnia. Graded cooling produced a progressive reduction in the changes in maximal tracheal pressure and phrenic nerve discharge responses caused by hypercapnia. Cooling the intermediate area to 20 degrees C significantly elevated the CO2 thresholds of both responses. These findings demonstrate that structures near the intermediate area of the VMS play a role in the neural cholinergic responses of the tracheal segment to CO2. It is possible that neurons or fibers in intermediate area influence the motor nuclei innervating the trachea. Alternatively, airway tone may be linked to respiratory motor activity so that medullary interventions that influence respiratory motor activity also alter bronchomotor tone.

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