The effect of α-, β adrenergic receptor agonists and antagonists on the efflux of 22Na and uptake of 42K by rat brain cortical slices

Abstract

The effects of norepinephrine on ion fluxes in rat brain cortical slices have now been ascertained. 22Na efflux and 42K influx are enhanced by norepinephrine. The increase in ion fluxes can be blocked by ouabain, phentolamine and propranolol, suggesting that the catecholamine activates a membrane sodium pump by a receptor-mediated step. The facilitation of 22Na efflux is stereospecific as demonstrated by the very weak action of d-norepinephrine at 10 −5 M concentration. Various α-adrenergic and β-adrenergic receptor agonists, including oxymetazoline, naphazoline, clonidine, tramazoline, methoxamine, phenylephrine, l-isoproterenol and methoxyphenamine are potent stimulants of the sodium pump as demonstrated by their enhancement of ion fluxes in rat brain cortical slices. Our results are consistent with the hypothesis that norepinephrine hyperpolarizes central neurons by activating an ouabain-sensitive, receptor-mediated sodium pump.