Localization and quantification of 5-hydroxytryptophan and serotonin in the central nervous systems of Tritonia and Aplysia.

Serotonin (5-hydroxytryptamine, 5-HT) plays a central role in several behaviors in marine molluscs and other species. In an effort to better understand the regulation of 5-HT synthesis, we used high performance liquid chromatography (HPLC) with electrochemical detection and immunohistochemistry to measure and map the distribution of the immediate precursor of 5-HT, 5-hydroxytryptophan (5-HTP), in two model opisthobranch molluscs, the nudibranch Tritonia diomedea and the anaspid Aplysia californica. HPLC measurements showed that 5-HTP is present at approximately the same level as the 5-HT metabolite, 5-hydroxyindolacetic acid (5-HIAA) but is more than 100 times lower in concentration than either 5-HT or dopamine in the same tissue. Specific 5-HTP immunoreactivity was colocalized with serotonin in both species. The overall intensity of 5-HTP immunoreactivity in individual ganglia agreed with HPLC measurements for those ganglia. The intensity of 5-HTP immunolabeling varied between cell types and was correlated with the intensity of 5-HT immunolabeling. In particular, differences in staining intensity were consistently seen among the three dorsal swim interneurons of the Tritonia swim central pattern generator circuit. Some nonserotonergic neurons also displayed low levels of 5-HTP immunolabeling that were above background levels. Together, these results support the notion that production of 5-HTP is a rate-limiting step in serotonin synthesis and suggest that there may be additional regulation that allows 5-HTP to accumulate to varying levels.

[Immune mechanism of regulating the balance of chemical compounds of endogenous origin]. / Ob immunnom mekhanizme reguliatsii balansa khimicheskikh soedinenii éndogennogo proiskhozhdeniia.

Specific autoantibodies of neutralizing character to histamine, serotonin, kallikrein, bradykuinine, acetylcholine, adrenalin, noradrenalin, insulin, and to the serotonin metabolite--5-hydroxyindolacetic acid, were found in donor serum (47.2%) and in intact rabbits, guinea pigs, rats, and mice (24.4%). Anti0odies to histamine, serotonin, kallikrein were found in a number of samples of commercial gamma-globulin. They were relatively often observed during the morning and day-time hours, in summer and in winter, in luteal phase of menstrual cycle, early in pregnancy (6-8 weeks), after surgical treatment, burns, inflammation, administration of foreign albumin, in the course of immunization by different antigens. The results of fractional analysis of serum showed that antibodies belonged to immunoglobulins with the constant of sedimantation 7S and 19S. The data obtained suggest the existence of an immune mechanism for the content regulation of different substances of endogenous origination in any organism.