Effects of injection of selective adrenergic receptor antagonists into the lateral hypothalamic area on renal function

ABSTRACT

Studies were underlaken to characterize the participation of specific alpha-1, alpha-2 and beta adrenoceptors of the lateral hypothalamic area *LHA) in the urinary excretion of sodium and potassium. Alpha-1 and alpha-2 IHA receptors were shown to participate in the regulation of renal sodium and potassium excretion. the effects of noradrenaline microinjection (30 nmol in 1 micronl) into the LHA on urinary sodium excretion (UNaV) are blocked by previous injection of the alpha-1 antagonist prazosin (4 nmol in 1 micronl) from 3.22 ñ 0.25 to 0.59 ñ 0.04 micronEq min-1 100g body weigh-1. Pre-injection of yohimbine, an alpha-2 antaghonist (4 nmol in 1 micronl), synergistically potentiated the action of noradrenaline on UNaV (3.22 ñ 0.25 to 4.02 ñ0.27 micronEq min-1 100g body weight-1) and on urinary potassium excretion (UKV) (0.70 ñ 0.08 to 1.15 ñ 0.12 micronEq min-1g body weight-1). The beta-adrenergic blockers metoprolol (100 nmol in 1 micronl) and propranolo (100 nmol in 1 micronl) had no sunergistic or antagonistic action on the sodium excretion fraction, suggesting that neither of these recptors in present in the LHA. Our results indicate that natriuresis occurs even in the absence of changes in glomerular filtration rate and demonstrate an inhibitory natriuretic effect of an alpha-1 blocker (prazosin) injected into the LHA before adrenaline, wile an alpha-2 antagonsit (yohimbine) yielded a potentiating effect (AU)ñ