UPTAKE OF EXOGENOUS CATECHOLAMINES BY MONOAMINE-CONTAINING NEURONS OF THE CENTRAL NERVOUS SYSTEM: UPTAKE OF CATECHOLAMINES BY ARCUATO-INFUNDIBULAR NEURONS

¹ Department of Pharmacology, University of Zurich, Zurich, Switzerland

The uptake of norepinephrine (NE), epinephrine (E), dopamine (DA) and 3,4-dihydroxyphenylalanine (dopa) into the mouse brain has been studied by means of the histochemical fluorescence method of Falck. Prior to the intraperitoneal administration of one of the catecholamines or of dopa, the amine stores were depleted by reserpine and monoamine oxidase was inhibited by Nialamide. In addition, azapetine was given shortly before high doses of NE or E. The animals were killed 5 hr after reserpine, when no green fluorescence (indicating the presence of a catecholamine) was observed in the controls. The uptake of NE administered in high doses was found to be limited to nerve cell bodies in the nucleus arcuatus, with axons descending to the external layer of the median eminence, nucleus periventricularis anterior and posterior hypothalami, area retrochiasmatica, area postrema and bulbus olfactorius and nerve endings in the median eminence. After smaller doses of NE the fluorescence intensity decreased accordingly. After DA and E, only a weak green fluorescence developed in these neurons even if high doses were given. The existence of a catecholamine-containing arcuatoinfundibular neuron is indicated by the demonstration of green fluorescent axons which connect green fluorescent nerve cell bodies in the arcuate nucleus with their nerve endings in the median eminence. In both regions, green fluorescent nerve cells and nerve endings respectively are also found in normal, untreated animals. The nerve endings are situated in the region of the primary plexus of the hypophyseal portal system.