The release of [3H]norepinephrine from isolated mouse vas deferens has been measured. 1-Phenylephrine and 1-norepinephrine significantly enhanced the spontaneous release of radioactivity. As shown by a combination of HPLC and scintillation spectrometry, the release of total radioactivity in response to 1-phenylephrine or 1-norepinephrine consisted mainly of [3H]norepinephrine. Evidence has been obtained that the release of endogenous norepinephrine by exogenous norepinephrine and 1-phenylephrine is independent of the external Ca2+ concentration. The released endogenous norepinephrine in turn inhibits the release of norepinephrine in response to electrical field stimulation. In the presence of yohimbine, the enhancement of spontaneous release due to 1-phenylephrine (or to 1-norepinephrine) was not affected, whereas there was a significant superimposed release of [3H]norepinephrine in response to field stimulation, indicating that the inhibition of stimulation-induced norepinephrine release is an alpha 2-adrenoceptor-mediated process. An important consequence of these findings is to question previous interpretations that the effects of administration of 1-norepinephrine or 1-phenylephrine are due exclusively to their direct effec...Continue Reading
Adrenergic receptor trafficking is an active physiological process where adrenergic receptors are relocated from one region of the cell to another or from one type of cell to another. Discover the latest research on adrenergic receptor trafficking here.