Effect of captopril on sympathetic preganglionic efferent activity in cats.
In 13 decerebrate cats, we studied the effects of captopril (10 mg/kg iv bolus) on the background discharge of thoracic preganglionic sympathetic fibers. After drug administration there was an initial reduction in systolic arterial pressure (SAP), which was followed by a later inhibition of sympathetic discharge (from 2.7 +/- 0.5 to 0.79 +/- 0.1 imp/0.1 s; P < 0.01). Captopril significantly reduced the excitatory response of sympathetic fibers to premature ventricular contraction (70 +/- 17 vs. 257 +/- 30%), inferior vena cava obstruction (176 +/- 56 vs. 315 +/- 85%) and asphyxia (143 +/- 20 vs. 245 +/- 51%). Vice versa the sympathetic response to aortic occlusion was unaffected (-58 +/- 8 vs. -62 +/- 6%). A similar reduction in sympathetic discharge was observed after captopril administration in anesthetized cats (n = 3). On the contrary, no changes in background neural discharge were noticed in decerebrate-spinalized cats (n = 5), despite comparable hemodynamic effects. These data indicate that captopril reduces sympathetic efferent activity and its responsiveness to excitatory stimuli. The lack of neural effects in decerebrate-spinalized cats is consistent with a brain stem site of action of captopril.
Montano
N
N
Centro Ricerche Cardiovascolari, Università di Milano, Italy.
Gnecchi-Ruscone
T
T
Contini
M
M
Finocchiaro
M L
ML
Lombardi
F
F
Malliani
A
A
D000818:Animals; D002216:Captopril / Q000494:pharmacology*; D002415:Cats; D003655:Decerebrate State; D004525:Efferent Pathways / Q000187:drug effects / Q000502:physiology; D004594:Electrophysiology; D005728:Ganglia, Sympathetic / Q000187:drug effects* / Q000502:physiology; D012018:Reflex / Q000187:drug effects
D002216:Captopril