1964 



Welsh, John H. 1943. 



Acetylcholine level of rat cerebral cortex under conditions of anoxia and 

 hypoglycemia. J. Neurophysiol. 6(5-6): 329-336. 



Among several assay methods used was isolated heart preparation of Venus 

 meroenaria. Venus heart apparently is unaffected by substances other than 

 ACh in tissue suspensions at the great dilutions used. (Abstracter's note: 

 because it is so extremely sensitive to acetylcholine (ACh) Venus heart can 

 be used to assay ACh with very dilute extracts and thus reduce to a minimum 

 the possibility of interference by other substances.) - J.L.M. 



1965 



Welsh, John H. 1948. 



IV. Concerning the mode of action of acetylcholine. Bull. Johns Hopkins 

 Hosp. 83: 568-579. 



Isolated heart of Venus meroenaria, like some other biological preparations, 

 is sometimes excited, sometimes inhibited, by acetylcholine (ACh). Complete 

 stoppage of heart occurs at concentrations about 50 times the threshold 

 concentration for inhibition. This suggests that an enzyme system is 

 involved directly in the action of ACh. Venus heart has very little 

 cholinesterase, which accounts for the very slight potentiation of ACh action 

 by anti-cholinesterases. When ethyl radicals are substituted for methyl in 

 the onium group of choline or ACh, activity is lost, and relatively high 

 concentrations are without effect. This directs attention to this portion 

 of the molecule, and the action of quaternary ammonium compounds on Venus 

 heart becomes of interest. The pentavalent nitrogen with its 3 methyl 

 groups becomes, in certain respects, the most significant part of the ACh 

 molecule. The rapidity with which ACh in small amounts acts on Venus heart 

 suggests that it is acting as a "trigger" to set off a reaction or chain of 

 reactions. The specificity of the (CH3)3N group suggests that size and 

 configuration are important. Rapid recovery of heart after washing and rapid 

 blocking action of quaternary ammonium ions other than tetra methyl ammonium, 

 when present with ACh in the medium surrounding the heart, suggest that ACh is 

 acting at or near the surface of the smooth muscle membrane. It is suggested 

 that ACh may play a role in regulation of cellular metabolism and growth. 

 This more general role of ACh could account for its wide distribution in plants 

 and animals. ACh may act as a coenzyme to regulate activity of an enzyme or 

 receptive substance in or near the cell membrane, which alters excitability of 

 the cell. The instability of ACh makes it a possible regulator of a process 

 that must be started and stopped quickly. - J.L.M. 



1966 



Welsh, John H. 1953. 



The occurrence of an excitor amine in the nervous system of Buooinium and its 

 action on the heart. Anat. Rec. 117(3): 637-638 (abstract 232). 



Regulatory nerves of molluscan hearts, including Venus meroenaria, appear to 

 produce opposing mediators. Evidence thus far obtained identified the excitor 

 agent as 5-hydroxytryptamine. - J.L.M. 



1967 



Welsh, John H. 1953. 



Excitation of the heart of Venus meroenaria. Arch. Exper. Pathol. Pharmakol. 

 219: 23-29. 



Isolated heart of Venus meroenaria is excited by compounds known to be 

 acetylcholine (ACh) antagonists, probably by blocking endogenous ACh. Certain 

 ergot alkaloids excite Venus heart in low concentrations and strongly resist 

 washing out. They may be removed from heart tissue with alkaline wash fluid. 

 Adrenalin, noradrenalin, tyramine, and histamine excite at relatively high 

 concentrations. 5-Hydroxytryptamine (5-HT) , also known as enteramine or 

 serotonin, excites Venus heart at concentrations as low as 10 - 10m. Electrical 

 stimulation of regulatory nerves to the heart has an effect similar to that 



547 



