Differential effects of rANF and chronic guanabenz to presynaptic and postsynaptic alpha 2-adrenoceptor-mediated cardiovascular response in pithed rats.
1. In normal rats, intracerebroventricular (i.c.v.) guanabenz induced a decrease in blood pressure (BP) and heart rate (HR), and this hypotension or bradycardia was not changed by rANF pretreatment (3 micrograms i.c.v.). 2. In pithed rats, intravenous (i.v.) guanabenz, an alpha 2-adrenoceptor agonist, produced an increase in mean blood pressure (MBP) in a dose-dependent manner. The pressor response by guanabenz was attenuated by infusion of rANF. This attenuation was additive when incubated in combination with yohimbine. 3. In pithed rats, the pressor response due to the increase of sympathetic outflow with electrical stimulation was partially blocked by rANF infusion or chronic guanabenz treatment. This reduction was not augmented by chronic guanabenz plus rANF treatment. 4. The inhibitory action of guanabenz in tachycardia evoked by electrical stimulation at the C7-T1 site was attenuated by rANF, but not by chronic treatment with guanabenz.
Sohn
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UD
Department of Pharmacology, College of Pharmacy, Chung Ang University, Seoul, Republic of Korea. udsohn@cau.ac.kr
Choi
H C
HC
D000316:Adrenergic alpha-Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects; D003655:Decerebrate State / Q000503:physiopathology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006143:Guanabenz / Q000008:administration & dosage / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018341:Receptors, Adrenergic, alpha-2 / Q000187:drug effects* / Q000502:physiology; D017661:Receptors, Presynaptic / Q000187:drug effects* / Q000502:physiology
D000316:Adrenergic alpha-Agonists; D018341:Receptors, Adrenergic, alpha-2; D017661:Receptors, Presynaptic; D010656:Phenylephrine; D009320:Atrial Natriuretic Factor; D006143:Guanabenz