Multiple Receptors and Binding Sites for Tachykinins

The evidence for the existence of multiple classes of receptor for the naturally occurring tachykinins has been reviewed previously [1–4]. Our original proposal for a sub-division of SP-P and SP-E receptors [1] was based on pharmacological data. showing differences in the relative potencies of tachykinins in different peripheral tissue bioassays. These differences have since been confirmed in other laboratories [5,6]. More recently. several different radiolabelled tachykinin derivatives have been used to characterise tachykinin receptors in peripheral tissues and in CNS. Using binding studies [7–10]. Such studies have suggested that there may be three rather than two types of tachykinin receptor binding sites in mammalian tissues. and some of these findings will be reviewed here and by the contributors to this symposium session.