An evaluation of the use of intraventricularly administered [3H]5-hydroxytryptamine as a marker for endogenous brain 5-hydroxytryptamine.
Following the intraventricular injection of a small amount of [3H]5-hydroxytryptamine ([3H]5-HT), the amount of radioactivity in telencephalic structures on the injected side was 6--7 times larger than that in corresponding areas on the opposite side. Moreover, a multiphasic disappearance of [3H]5-HT from whole brain or midbrain was found after the intraventricular injection of the labeled amine. However, after the intraventricular injection of [3H]tryptophan, the levels of [3H]5-HT in midbrain declined in a monophasic manner. A significant portion of the labeled amine derived from intraventricularly administered [3H]5-HT was resistant to the depleting effect of Ro4-1284 or to that elicited by destruction of the midbrain raphe nuclei, both of which caused an almost complete loss  of endogenous 5-HT and labeled 5-HT formed from tryptophan. It thus appears that the intraventricular injection of [3H]5-HT leads to the formation of artifactual pools which are not present if the amine is synthesized in vivo. Studies with 6-hydroxydopamine suggested, however, that uptake of [3H]5-HT into adrenergic neurons did not occur to any great extent.
D012369:2H-Benzo(a)quinolizin-2-ol, 2-Ethyl-1,3,4,6,7,11b-hexahydro-3-isobutyl-9,10-dimethoxy- / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000187:drug effects; D001923:Brain Chemistry; D002552:Cerebral Ventricles / Q000378:metabolism; D006624:Hippocampus / Q000378:metabolism; D006892:Hydroxydopamines / Q000494:pharmacology; D006897:Hydroxyindoleacetic Acid / Q000032:analysis; D007267:Injections; D008297:Male; D008636:Mesencephalon / Q000187:drug effects / Q000378:metabolism; D008722:Methods; D051381:Rats; D012701:Serotonin / Q000032:analysis* / Q000096:biosynthesis / Q000378:metabolism; D013687:Telencephalon / Q000378:metabolism; D013997:Time Factors; D014316:Tritium; D014364:Tryptophan / Q000378:metabolism
D006892:Hydroxydopamines; D014316:Tritium; D012369:2H-Benzo(a)quinolizin-2-ol, 2-Ethyl-1,3,4,6,7,11b-hexahydro-3-isobutyl-9,10-dimethoxy-; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D014364:Tryptophan