AJP - Heart and Circulatory Physiology, Vol 249, Issue 1 64-H70, Copyright © 1985 by American Physiological Society
Enhanced depressor effect of bromocriptine in the DOCA/NaCl hypertensive rat
S. Nagahama, Y. F. Chen and S. Oparil
To elucidate the role of the dopaminergic system in the maintenance of
hypertension in the deoxycorticosterone acetate (DOCA)/NaCl hypertensive
rat, the responses of mean arterial pressure (MAP), plasma norepinephrine
(NE), epinephrine (E), and prolactin (PRL) to intravenous (iv)
administration of bromocriptine, a dopamine agonist, and hexamethonium
bromide, a ganglion blocker, were examined in conscious, unrestrained 4-wk
DOCA/NaCl hypertensive rats. Bromocriptine was administered to
adrenomedullectomized (ADMX) rats to assess the role of the adrenal medulla
in its depressor effect. Bromocriptine (50, 250, and 500 micrograms/kg) and
hexamethonium (3 and 30 mg/kg) caused dose-dependent decreases in MAP that
were greater in DOCA/NaCl rats than in uninephrectomized controls. Basal
plasma NE, E, and PRL were significantly higher in DOCA/NaCl rats than in
controls. Bromocriptine (500 micrograms/kg iv) decreased plasma PRL to
undetectable levels and increased plasma E significantly without changing
NE levels in DOCA/NaCl and uninephrectomized control rats. In ADMX rats
bromocriptine (500 micrograms/kg iv) decreased MAP, PRL, and NE without
affecting E levels. These results suggest that the depressor response to
bromocriptine could be related to inhibition of sympathetic outflow without
participation of the adrenal medulla. The hyperprolactinemia and enhanced
depressor response to bromocriptine observed in DOCA/NaCl animals suggest
that the dopaminergic system might be altered in this model of
hypertension.
