invertebrate examined. Venus ganglia synthesized from added 5-hydrox- 

 ytryptophan (5-HTP) from 50 to over 250 ug 5-HT/g of tissue in 3 hrs. 

 Evidence was found for a seasonal variation in 5-HTP decarboxylase levels. 

 With blood as an incubation medium, addition of marsilid (l-isonicotinyl-2- 

 isopropyl hydrazide) , which was used as an inhibitor of amine oxidase, 

 usually increased slightly the amount of 5-HT found. Pyridoxal phosphate was 

 used in some experiments because it had been shown to be a cofactor for 5-HTP 

 decarboxylase. This compound, for some unknown reason, sometimes increased 

 the amount of 5-HT, but sometimes reduced it. (Abstracter's note: the 

 bibliography to this paper, containing 20 references, was not searched 

 because titles were not given. It is probable that all pertinent papers were 

 located by other means.) - J.L.M. 



1983 



Welsh, John H., and Merilyn Moorhead. 1959. 



Identification and assay of 5-hydroxytryptamine in molluscan tissues by 

 fluorescence method. Science 129(3361): 1491-1492. 



Earlier identification of 5-hydroxytryptamine (5-HT, serotonin, enteramine) 

 in nerve tissue of Venus mercenaria and Busycon has been confirmed. Content 

 of 5-HT in various tissues of V. mercenaria ranged from 30 yg/g in pooled 

 ganglia to less than 0.004 ug/g in blood. No tissues other than ganglia had 

 a value as high as 1 ug/g. The rather large spread of values (12-52 yg/g 

 in ganglia) reflected seasonal and individual variations in 5-HT content, and 

 difficulty of freeing the small, fragile Venus ganglia of surrounding tissue. 

 Low levels of 5-HT in non-nervous tissues may be derived from nerve endings. 

 Ganglia of Busyaon eanalioulatum contained less than 1/3 as much 5-HT as those 

 of Venus. - J.L.M. 



1984 



Welsh, John H., and Merilyn Moorhead. 1960. 



The quantitative distribution of 5-hydroxytryptamine in the invertebrates, 

 especially in their nervous systems. J. Neurochem. 6(2): 146-169. 



5-Hydroxytryptamine (5-HT), also known as serotonin or enteramine, is 

 distributed in a variety of cells and tissues of plants and animals. Its 

 unusual distribution, and the probable multiple role of 5-HT, have diverted 

 attention from what may be its most important single function, that of a 

 neurohumor. 5-HT has been found in tissues of many invertebrates, including 

 ganglia of Venus mercenaria, in fresh tissue of which the average con- 

 centration is 40.0 ug/g. No consistent differences in 5-HT levels of 

 different ganglia of Venus were found. Earlier estimates of 5-HT values in 

 Venus ganglia were too low, probably because remnants of other tissues were 

 present. The present value of 40 ug/g is one of the highest for any nervous 

 tissue. Equivalent amounts of 5-HT of nervous origin are found only in other 

 bivalves. No organ or part of Venus outside the nervous system contained more 

 than 0.75 ug/g (mantle edge), and none was detected in blood. Lower amounts 

 of 5-HT occur in Venus nerve than in ganglia, which suggests that it is 

 concentrated in cell bodies or nerve terminals. The 5-HT found in Venus 

 heart, mantle, and other non-nervous tissues may derive from nerve endings. 

 More primitive and less specialized invertebrates appear to have more 5-HT 

 in their nervous systems than do more specialized forms. - J.L.M. 



1985 



Welsh, John H., and Alan G. Slocombe. 1952. 



The mechanism of action of acetylcholine on the Venus heart. Biol. Bull. 

 102(1): 48-57. 



Large Venus mercenaria from Narragansett Bay were used. When heart was 

 stimulated with a train of impulses at 10/sec for 30 sec an inhibition 

 similar to that produced by acetylcholine (ACh) was observed. Stimulation 

 with direct current produced negative intropic, chronotropic, and tonotropic 

 effects when anodal, and positive chronotropic and tonotropic effects when 

 cathodal. This reversibility with changing polarity was interpreted to mean 

 that the step in the regulatory process influenced by electrical stimulation 

 is fundamentally electrical. Chemical response to electrical stimulation was 



552 



