PARABRACHIAL NUCLEI--ROLE IN RESPIRATORY SYSTEM DEFENSE

Research project

Description

One response to inhaled noxious aerosols is an abrupt termination of
inspiration. This reflex is elicited by the branch of trigeminal
nerve that innervates the nasal mucosa. If irritants persist in the
upper airway or enter the lower airway, then more complex changes
occur in the breathing pattern. Central mechanisms forming these
integrated responses, especially those elicited by the trigeminal
nerve, are poorly understood. We hypothesize that the pontine
respiratory group (PRG), a bilateral structure in the rostral, dorso-
lateral pons, is a major nucleus necessary for the incorporation of
sensory stimuli into the central pattern generator for respiration.
Specifically, we believe that the PRG shapes the breathing pattern in
response to stimulation of the nasal mucosal, laryngeal, and
intrathoracic airway receptors. Furthermore, we hypothesize that PRG
neurons that are poorly correlated with respiration are more
responsive to sensory stimulation and are more sensitive to changes
in state of consciousness than those neurons whose activity is highly
modulated by respiration. We propose a set of neurophysiologic experiments in both anesthetized
and unanesthetized cats to determine if airway afferent and PRG
activities terminate inspiration through post-inspiratory neurons and
if more complex reshaping of the breathing pattern is dependent on
the PRG. We will record inspiratory, expiratory and post-inspiratory
motor unit activity and compare their responses to stimulation of
trigeminal and superior laryngeal nerves before and after injection
of cobalt in the PRG. We will stimulate subregions of the PRG
chemically and electrically and record short-latency responses of
medullary post-inspiratory neuronal and respiratory muscle activity
and of respiratory timing (TI,TE,TTOT). We will use quantitative
methods for determining the relationship between recorded PRG neural
activity and respiration. This correlation reflects a balance
between respiratory and non-respiratory synaptic drive to a neuron.
A weakly correlated and poorly modulated cell reflects a predominance
of non-respiratory inputs. The aims are to: 1) compare the muscle and timing responses to
airway-afferent stimulation before and after blocking synaptic
transmission in the PRG, 2) determine the pattern of respiratory
muscle activity elicited by microstimulation of the PRG, 3) analyze
the activity patterns of PRG neurons and correlate their behavior to
their responses to afferent stimulation and to changes in state of
consciousness and 4) analyze the response of medullary post-
inspiratory neurons, neurons that are excited by superior laryngeal
nerve stimulation, to trigeminal nerve and PRG stimulation. Results
will provide insight into the neurophysiologic mechanisms for
influence of PRG and airway afferent information on medullary
stimulation, weakly and strongly modulated PRG neurons, and medullary
post-inspiratory neurons. Such interaction may be relevant to
understanding changes in the breathing pattern with activation of
upper and lower airway afferent nerves during inflammation and
irritation.
StatusFinished
Effective start/end date3/1/922/28/98

Funding

  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health: $157,120.00
  • National Institutes of Health: $6,543.00
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health: $13,087.00

Fingerprint

Respiratory System
Neurons
Parabrachial Nucleus
Respiration
Trigeminal Nerve
Laryngeal Nerves
Respiratory Muscles
Consciousness
Central Pattern Generators
Pons
Nasal Mucosa
Irritants
Cobalt
Aerosols
Nose
Reaction Time
Reflex
Cats
Inflammation
Muscles

Keywords

  • Medicine(all)