Table 8

Receptor type codes

 1.  For well established classifications, the receptor type category will be represented by an upper case alphanumeric code that is recognizable as analogous to the trivial nomenclature, e.g., for the G protein-coupled serotonin receptors (see Hoyer et al., 1994; Eglen et al.,1997): 2.1.5HT.01A. for the 5-HT1A receptor 2.1.5HT.01B. for the 5-HT1B receptor 2.1.5HT.01D. for the 5-HT1D receptor 2.1.5HT.02A. for the 5-HT2A receptor 2.1.5HT.07. for the 5-HT7 receptor, etc. 2.1.ADR.A1A. for the α1A adrenoceptor 2.1.ADR.B1. for the β1 adrenoceptor, etc. 2.  Where subclassification has not been attempted, a simple chronological numeric code may be assigned, although this approach seems scientifically parsimonious and circumvents an opportunity to provide additional classifying information (e.g., as for dopamine receptors; see Humphrey, 1998).8-a 2.1.DA.01. 2.1.DA.02., etc.

The use of an alphanumeric abbreviation for the receptor type category would allow either for recognizable reference to trivial names or direct reference for more recently identified receptors to the simple numbering system used by molecular biologists. Parenthetically, it is suggested that in some cases, for example the muscarinic acetylcholine and dopamine receptor families, consideration should be given as to whether the latter current schemes are still appropriate (see Humphrey, 1997). Regardless, the two options for designating an RC are outlined below and each subcommittee could choose one for their receptor family.

• 8-a It is recognized that there is a view strongly held by some that an arbitrary numeric code should be used for all receptor types, which would circumvent past problems associated with incorrectly assigning trivial names. However, after much discussion at NC-IUPHAR meetings, it was agreed that many pharmacologists would not readily accept a system which, for example, groups together the adrenoceptor family without distinguishing between alpha and beta types, with their very different pharmacological characteristics. Nevertheless, if consistent yet arbitrary numeric codes were considered desirable in the future, it would be simple to number each receptor type according to its established position in the database.