[Origin and role of circulating catecholamines in the normotensive sympathectomized rat].
Early chronic treatment with guanethidine destroys peripheral sympathetic nerves while sparing the adrenal medulla, and does not lower blood pressure (BP) in conscious normotensive rats (Julien et al. Am J Physiol 1990; 259: H1337). Therefore, the origin and role of circulating catecholamines (CAs) in BP maintenance were examined in conscious normotensive control, sympathectomized (SNX)--daily s.c. injections of guanethidine from 1 to 13 weeks of age--and sympathectomized-adrenalectomized (SNX-A) rats by measuring i) their plasma CAs (norepinephrine, NE and epinephrine, E) and 3,4-dihydroxyphenylglycol (DHPG) by HPLC-FD, and ii) their mean BP (MBP) responses to phenylephrine and phentolamine (5 mg/kg i.v.). The doses of phenylephrine that produced similar MBP rises were 3 micrograms/kg in controls (44 +/- 4 mmHg) and 1.5 micrograms/kg in SNX (47 +/- 3 mmHg) and SNX-A (48 +/- 2 mmHg) rats. Results are as follows: [table: see text] In conclusion, in conscious normotensive SNX rats: (1) most of the circulating NE is of adrenomedullary origin and plasma DHPG derives from neuronal NE; (2) due to supersensitivity of the cardiovascular system, stimulation of alpha-adrenoreceptors by circulating CAs play a significant role in BP maintenance.
Lo
M
M
Département de physiologie et pharmacologie clinique, URA CNRS 606, faculté de pharmacie, Lyon.
Julien
C
C
Boomsma
F
F
Barrès
C
C
Sassard
J
J
D000313:Adrenal Medulla / Q000502:physiology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002395:Catecholamines / Q000096:biosynthesis / Q000097:blood / Q000502:physiology*; D006145:Guanethidine; D008297:Male; D010646:Phentolamine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D013563:Sympathectomy, Chemical
D002395:Catecholamines; D010656:Phenylephrine; D010646:Phentolamine; D006145:Guanethidine
Origine et rôle des catécholamines circulantes chez le rat normotendu sympathectomisé.