Augmentation of muscle nociceptive respiratory reflex facilitation by vagal afferents.
Vagal influence on the facilitation of phrenic neural activity during respiratory phase-locked, gastrocnemius muscle nerve nociceptive electrical stimulation was examined in anesthetized, glomectomized, paralyzed, and artificially ventilated cats. (1) In the vagi-intact state, respiratory reflex facilitation was characterized by a sharp rise in peak amplitude, maximum rate of rise or slope, and mean rate of rise of integrated phrenic nerve activity. This was greater during inspiratory phase-locked (T1-locked) muscle nerve electrical stimulation than during expiratory phase-locked (TE-locked) muscle nerve electrical stimulation. "Evoked post-inspiratory phrenic activity" during the early expiratory phase was also observed during TE-locked muscle nerve electrical stimulation. (2) Bilateral vagotomy significantly attenuated the respiratory facilitation during both T1- and TE-locked muscle nerve electrical stimulation. In particular, the "evoked post-inspiratory phrenic activity" during TE-locked muscle nerve electrical stimulation was also attenuated or almost completely abolished. (3) Conditioning electrical stimulation of the vagus nerve revealed facilitatory reflexes which co-exist with inspiratory inhibitory reflexes. (4) The "evoked post-inspiratory phrenic activity" during TE-locked muscle nerve electrical stimulation, which was attenuated or abolished after vagotomy, was restored after vagal T1-locked conditioning stimuli combined with TE-locked muscle nerve electrical stimulation. The results suggest that vagal facilitatory reflexes augment the respiratory reflex facilitation during muscle nociceptive stimulation.
Department of Nervous and Sensory Functions, Nagoya University, Japan.
D
D
Simbulan
E
E
Tadaki
Y
Y
Kozaki
K
K
Eguchi
T
T
Kumazawa
D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D002415:Cats; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000502:physiology; D009469:Neuromuscular Junction / Q000502:physiology; D009619:Nociceptors / Q000502:physiology*; D012018:Reflex / Q000502:physiology*; D015656:Respiratory Mechanics / Q000502:physiology*; D012132:Respiratory Muscles / Q000502:physiology; D014628:Vagotomy; D014630:Vagus Nerve / Q000502:physiology*