Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0085383 (hypocapnia)
 1,697 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Agents which depress respiration, such as alcohol, seem to increase the occurrence of obstructive apneas during sleep. It has been proposed that upper airway obstruction can result from an imbalance in the activity (or forces) produced by the upper airway muscles versus the chest wall muscles so that upper airway passages might be blocked when a disproportionate decrease in upper airway muscle activity occurs. This study examines the hypothesis that depression of respiration affects the activity of the hypoglossal nerve (the motor nerve to the tongue) more than the activity of the phrenic nerve (the motor nerve to the diaphragm). In addition, we examined the role of the putative central chemoreceptor area on the ventrolateral medullary surface (VMS) in maintaining phrenic and hypoglossal discharge. In chloralose-anesthetized, artificially ventilated, paralyzed cats, three methods of reducing respiratory drive were studied: hyperoxic hypocapnia (produced by mechanical hyperventilation), the application to the intermediate area of the ventral medullary surface of the respiratory depressant GABA and its agonist muscimol, and cooling the same area of the VMS (using a water-cooled thermode). All these interventions decreased hypoglossal nerve activity more than phrenic nerve activity (range of p values: p less than 0.001 to p less than 0.01). Moreover, the reduction in hypoglossal activity was greater with GABA and muscimol than with the other two maneuvers; this was statistically significant for both GABA versus VMS cooling (p less than 0.02) and muscimol versus VMS cooling (p less than 0.01). These results show that respiratory depression can differentially affect hypoglossal and phrenic nerve activity.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Responses of hypoglossal and phrenic nerves to decreased respiratory drive in cats. 374 14

Hypocapnia induced by hyperventilation (HV) has powerful effects on neuronal excitability and synaptic transmission. We have studied the effect of hyperventilation on the phase-locked oscillatory components of the evoked responses in the human brain. We recorded visually evoked magnetoencephalographic responses before, during, and after voluntary hyperventilation to pattern-reversal checkerboard stimuli. Gamma-band (30-45 Hz) responses phase-locked to the stimuli were generated in the occipital visual cortex. A wavelet-based time-frequency analysis revealed that the gamma responses increased during HV whereas their frequency did not change significantly. A recent in vitro study in the rat hippocampus demonstrated that the stability of spontaneous gamma activity increases during hypocapnia as a result of enhanced GABAergic transmission. To test if a similar mechanism could account for our findings, we performed simulations on a network of 100 Hodgkin-Huxley neurons connected by inhibitory synapses. We found that enhanced GABA(A) transmission, paired with enhanced excitability, can explain the increase in evoked gamma activity without changing the frequency.
 ...
PMID:Visually evoked gamma responses in the human brain are enhanced during voluntary hyperventilation. 1184