Inspiratory coupling to cardiac activity and to somatic afferent nerve stimulation in the anaesthetised rat

• Published in: Autonomic neuroscience Vol. 108; no. 1; pp. 45 - 49
• Main Authors: Larsen, P.D., Tzeng, Y.C., Galletly, D.C.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 31.10.2003; Elsevier
• Subjects: Anesthesia - methods; Animals; Biological and medical sciences; Cardiac activity; Electric Stimulation - methods; Fundamental and applied biological sciences. Psychology; Heart Rate - physiology; Inhalation - physiology; Inspiratory coupling; Male; Neurons, Afferent - physiology; Peripheral nervous system. Autonomic nervous system. Neuromuscular transmission. Ganglionic transmission. Electric organ; Rats; Somatic afferent nerve stimulation; Vertebrates: nervous system and sense organs; Somatic afferent nerve stimulation; Inspiratory coupling; Cardiac activity; Vertebrata; Mammalia; Rat; Autonomic nervous system; Animal; Rodentia
• ISSN: 1566-0702; 1872-7484
• DOI: 10.1016/j.autneu.2003.08.007

We examined the ability of somatic afferent nerve stimulation to entrain inspiratory onset in the anaesthetized spontaneously breathing rat, and compared features of this stimulus–ventilatory coupling to entrainment of inspiratory onset by cardiac activity. In 14 rats prior to stimulation, we commonly observed a constant temporal alignment between ECG R waves and inspiratory onset (cardioventilatory coupling). Stimulation of a hamstring nerve at rates close to the heart rate also caused coupling (a constant stimulus to inspiratory onset interval), although this was highly dependent upon frequency of stimulation, with small changes in frequency causing a loss of coupling. In experiments where stimuli were given at constant intervals after ECG R waves, we observed no augmentation of coupling. Our results indicate that both cardiac and somatic afferent nerve activity is able to entrain inspiratory onset. We have suggested that coupling causes respiratory frequency to increase, and it is possible that this is a general mechanism whereby non-respiratory afferents act as stimulants or pacemakers to respiratory rhythm. The role of non-respiratory activity in initiating inspiration needs to be more fully recognised and studied.