ULTRASTRUCTURAL CYTOCHEMISTRY AND PHARMACOLOGY OF 5-HYDROXYTRYPTAMINE IN ADRENERGIC NERVE ENDINGS. I. LOCALIZATION OF EXOGENOUS 5-HYDROXYTRYPTAMINE IN THE AUTONOMIC NERVES OF THE RAT VAS DEFERENS

¹ Instituto de Anatomia General y Embriologia, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Republica Argentina

Pharmacologic and electron microscopic cytochemical procedures were performed in the rat vas deferens in order to study the localization of exogenously administered 5-hydroxytryptamine (5-HT) in adrenergic nerve endings. Exogenous 5-HT accumulated in the nerve terminals was not incorporated into the intravesicular compartment, demonstrating that it is unable to displace norepinephrine from this storage site. Administration of -methyl-m-tyrosine markedly reduced the norepinephnine content of the vas deferens as well as the dense cores of the granulated vesicles of nerve endings. The administration of 5-HT to -methyl-m-tyrosine-pretreated rats resulted in a marked increase of 5-HT concentration in the organ and in the reappearance of the dense cores of both types of vesicles observed within the endings. That these cores corresponded to 5-HT was confirmed by the results of cytochemical tests. These data siggest that, under appropriate conditions, 5-HT can be incorporated and stored in the intravesicular compartment of the postganglionic sympathetic nerve endings normally storing norepmepllnine.