Continual recordings of cardiac sympathetic nerve activity in conscious sheep.
Cardiac sympathetic nerve activity (CSNA) is of major importance in the etiology of heart disease but is impossible to measure directly in humans. Ovine and human cardiovascular systems are similar; therefore, we have developed a method for the daily recording of CSNA in conscious sheep. After thoracotomy, electrodes were glued into the left thoracic cardiac nerve and CSNA, blood pressure (BP), and heart rate were recorded daily. Satisfactory recordings > or =7 days of CSNA were obtained in 11 of 28 sheep (40%), mean recording time 10.6 days, range 7-47. During the first week, CSNA decreased gradually from 78 +/- 8 at baseline to 60 +/- 7 bursts/min on day 5 (P = 0.02) or from 76 +/- 9 to 57 +/- 7 bursts/100 beats on day 7 (P = 0.04). Similarly, BP decreased from 103 +/- 4 to 94 +/- 4 mmHg (P = 0.03). Low-frequency heart rate variability decreased from 0.12 +/- 0.02 to 0.06 +/- 0.02 ms(2) on day 6 (P = 0.004) but was not correlated to CSNA. In conclusion, CSNA that can be continually recorded in conscious sheep decreases during the first week postsurgery and, thereafter, stabilizes. This model should provide valuable insights in future investigations of cardiac disease.
Jardine
David L
DL
Department of General Medicine, PO Box 4710, Christchurch Hospital, School of Medicine, Christchurch, New Zealand. david.jardine@cdhb.govt.nz
Charles
Christopher J
CJ
Melton
Ian C
IC
May
Clive N
CN
Forrester
Melanie D
MD
Frampton
Christopher M
CM
Bennett
Sinclair I
SI
Ikram
Hamid
H
D000818:Animals; D001794:Blood Pressure; D003243:Consciousness / Q000502:physiology; D004562:Electrocardiography; D005728:Ganglia, Sympathetic / Q000033:anatomy & histology / Q000502:physiology; D006321:Heart / Q000294:innervation*; D006339:Heart Rate; D012756:Sheep; D012890:Sleep / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000502:physiology*; D013908:Thoracotomy