FIELD T- 1 

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as simulating, by its action, a chemical whose action is already familiar to the author or is widely 

 known. Many compounds will come to mind whose actions have been so long observed and so 

 thoroughly measured that their actions are virtually classic standards. Examples of these are the 

 best known effects of digitalis, adrenaline, acetylcholine, curare, etc. However, compounds that 

 are less familiar than the examples named may be demonstrated by test data as being simulated by the 

 test compound. 



Besides considering "simulation" as restricted to comparison to chemicals whose simulated 

 action has previously been investigated and understood, it should be noted that generally an author 

 implies by the term "simulation" that the two compounds act through the same mechanism (i. e. , act 

 through the same anatomical, physiological, or biochemical paths) to bring about the specific response 

 such as reduction of heart rate, lowering of perspiration rate, increase of blood pressure, etc. 



Neither of these restrictions to the use of the term "simulation" for description of chemicals' 

 actions is absolute, but they are mentioned here to help explain that merely because two compounds 

 cause the same response, they are not always (or even frequently) specially described by an author 

 as simulating each other except when, by doing so, it assists significantly in describing a test 

 compound's action. 



Symbol A has been provided to code the fact that the test compound's action on the biological 

 state or physiological process coded in Field T-2 is essentially similar to the action of another 

 compound, to be coded in Field D. Simulation, as well as replacement, is ordinarily (although not 

 necessarily always) expressed by an author only under the restrictive conditions mentioned in the first 

 paragraphs of this division. Therefore, Symbol A is used only when an author states that the test 

 compound has been demonstrated to simulate or substitute for a specific secondary compound. Simu- 

 lation is sometimes expressed by the author with one of certain terms referring to a specific chemical 

 and implying all aspects characteristic of its action, such as "nicotinic", "muscarinic", or "atropinic", 

 For such data, nicotine, muscarine, or atropine would be coded in Field D and Symbol A would be 

 coded in Field T-l, assuming that the nicotinic, muscarinic, or atropinic effect was on a specific 

 biological state or physiological process coded in Field T-2. In case the author uses such terms 

 to describe a test compound's general effects on an organism without specifying a biological state 

 or process affected, this general simulation is not coded with Symbol A, but the general effect is 

 coded in Field T-3, if the appropriate term is available in Field T-3 (nicotinic effect, atropinic, etc. ), 

 Field T-2 is coded with Symbol 14 which refers to Field T-3, Field T-l is coded with Symbol 7 instead 

 of Symbol A, and it is unnecessary to code in Field D the compound simulated. 



When the compound simulated is a normal constituent of the organism or an essential dietary 

 component and the simulation is the test compound's ability to substitute adequately for that normally 

 occurring compound, the test compound is more frequently described as functionally "replacing" that 

 secondary compound than as simulating it. 



Each time the evaluation of a test compound's action is expressed in terms of comparison to a 

 standard (Criteria 03 or 04 of Field X), the situation involves two compounds that simulate each other, 

 even if their potencies for the action they both perform are not the same. 



Although Criteria 03 and 04 (Field X) necessarily involve two compounds simulating each other, 

 they can not be used for evaluating that simulation or replacement (i. e. , when Field T-l is coded with 

 Symbol A); in the reverse, when evaluation of a test compound's action is made on the basis of 

 Criterion 03 or 04, Symbol A should not be substituted in Field T- 1 for the action being so evaluated. 



Note that by using Field T-l to denote that a test compound's action simulates or replaces, 

 there is omitted any specification of the actual action performed and simulated. Therefore, a problem 

 exists similar to the problem of not being able to code the action when Field T-l is coded with Symbol 

 8, 9, or C, discussed in Division 12. 



When Symbol A is used to indicate that the test compound replaces a normal constituent or 

 dietary component, the role that constituent or dietary component normally plays in the organism need 

 not be recorded and therefore a second line especially to code this is not constructed. However, when 

 Symbol A is used to indicate that the test compound action simulates the action of a secondary 

 compound which is not a normal constituent or dietary component, the action simulated is not to be 

 construed by the CBCC coder as always obvious to every potential user of the coded information. When 



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