Centrally mediated increased sympathetic activity is not important in the genesis of ACTH-induced hypertension in sheep.
1. Adrenocorticotrophin (ACTH) administration to sheep produces a rapid adrenally dependent hypertension which is maximal after 3 days and associated with increased cardiac output (CO) and heart rate (HR), while calculated total peripheral resistance remains unchanged. 2. This study investigated the proposal that a centrally mediated increase in sympathetic activity is important in the development of ACTH-induced hypertension. 3. Concomitant intravenous infusions of either clonidine (60 micrograms/kg per day) or methyldopa (60 mg/kg per day) with ACTH (5 micrograms/kg per day) failed to inhibit the increase in mean arterial pressure (MAP) observed with ACTH. 4. In a separate experiment clonidine abolished the increase in CO and HR but not the pressor response associated with ACTH administration. 5. These results do not support a role for centrally mediated increase in sympathetic activity in the genesis of ACTH-induced hypertension.
Spence
C D
CD
Howard Florey Institute of Experimental Physiology and Medicine, Royal Melbourne Hospital, Parkville, Victoria, Australia.
Mathai
M
M
Mills
E H
EH
Coghlan
J P
JP
Whitworth
J A
JA
Scoggins
B A
BA
D000324:Adrenocorticotropic Hormone; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003000:Clonidine / Q000494:pharmacology; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006973:Hypertension / Q000139:chemically induced / Q000503:physiopathology*; D007275:Injections, Intravenous; D008750:Methyldopa / Q000494:pharmacology; D012756:Sheep; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D014655:Vascular Resistance / Q000187:drug effects
D008750:Methyldopa; D000324:Adrenocorticotropic Hormone; D003000:Clonidine