A control assay, using homogenate in which muscle cholinesterase was still 

 active, showed considerably less inhibition. The inhibitory effect could be 

 abolished totally by adding active serum cholinesterase to the homogenate 

 before the test, or by pretreating Venus heart with Mytolon, an ACh blocking 

 agent. Activity of extracts assayed against known quantities of 5-HT on 

 Venus heart proved equivalent to 1.0 yg 5-HT/g wet tissue. 5-HT and the 

 extract proved excitatory. 5-HT is of widespread natural occurrence. It 

 appears to be identical with enteramine, which has been detected in salivary 

 glands of Octopus and Eledone, in mammalian gastrointestinal mucosa and spleen, 

 intestine of Ciona and Tethium, and in skin of amphibia. The vasoconstrictor 

 principle first isolated from beef serum is the creatinine sulfate salt of 

 5-HT. Serotonin or a very similar substance is possibly released from brain 

 tissue. The mechanism of action of 5-HT was still unknown. - J.L.M. 



1849 



Twarog, Betty M. 1959. 



The pharmacology of a molluscan smooth muscle. British J. Pharmacol. 

 Chemother. 14(3): 404-407. 



Venus mercenaria is mentioned, but only by reference to papers by Welsh and 

 Taub (1953), Luduena and Brown (1952), and Welsh and McCoy (1957), abstracted 

 elsewhere in this bibliography. - J.L.M. 



1850 



Twarog, Betty M. 1960. 



Innervation and activity of a molluscan smooth muscle. J. Physiol. 152(2): 

 220-235. 



The paper deals with Mytilus edulis. Mercenaria (Venus) mercenaria is not 

 mentioned. - M.W.S. and J.L.M. 



1851 



Twarog, Betty M. 19 60. 



Effects of acetylcholine and 5-hydroxytryptamine on the contraction of a 

 molluscan smooth muscle. J. Physiol. 152(2): 236-242. 



The paper deals with Mytilus . Mercenaria (Venus) mercenaria is not 

 mentioned. - M.W.S. and J.L.M. 



1852 



Twarog, Betty M. 1967. 



The regulation of catch in molluscan muscle. J. Gen. Physiol. 50: 157-169. 



The paper deals with Mytilus. Mercenaria mercenaria is not mentioned. - 

 - M.W.S. 



1853 



Twarog, Betty M. 1968. 



Possible mechanism of action of serotonin on molluscan muscle. Adv. 

 Pharmacol. 6 B, Academic Press, New York: 5-15. 



Serotonin (5-hydroxytryptamine or 5-HT) causes relaxation of catch, 

 increased spiking, decreased membrane resistance, and stimulation of 

 metabolism of Mytilus smooth muscle. It has been speculated that 5-HT 

 controls translocation of intracellular Ca++. The chapter describes 

 experiments to test the validity of the proposed Ca++ - 5-HT interaction, 

 and provide further knowledge of the site of action of 5-HT in Mytilus 

 edulis . Mercenaria mercenaria is not mentioned. - J.L.M. 



514 



