Prazosin unmasks a renin response to intravenous para-chloroamphetamine.
When injected intraperitoneally, p-chloroamphetamine (PCA) causes the acute release of catecholamines and serotonin, increases mean arterial pressure (MAP) and increases plasma renin activity (PRA) in rats. Experiments were designed to determine the dose-response and time-course for the effect of PCA administered intravenously on PRA in conscious, unrestrained rats. It was found initially that intravenous doses of PCA ranging from 0.3 - 6.0 mg/kg caused rapid and marked hypertension, but produced variable effects on PRA for up to 30 minutes after injection. In a second study PCA (0.3 - 6.0 mg/kg) did not alter PRA at 30 or 60 minutes after intravenous injection, but did increase PRA 60 minutes after 10 mg/kg, intraperitoneally. When the hypertension elicited by intravenous PCA was abolished by pretreatment with the alpha 1-adrenoceptor antagonist prazosin (100 micrograms/kg, iv), PCA produced marked elevations in PRA from 15 - 60 minutes. Thus it appeared that the renin response to intravenous PCA was masked by an elevation in MAP; when the vascular response to PCA was blocked, a large increase in PRA was observed.
Alper
R H
RH
Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City 66103.
Pergola
P E
PE
Sippy
B D
BD
Zink
M H
MH
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D004347:Drug Interactions; D007275:Injections, Intravenous; D008297:Male; D011224:Prazosin / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012083:Renin / Q000097:blood*; D010133:p-Chloroamphetamine / Q000008:administration & dosage / Q000494:pharmacology*
D010133:p-Chloroamphetamine; D012083:Renin; D011224:Prazosin